Definition: infantile (juvenile) hemangioma is a form of capillary hemangioma which occurs during infancy.
Epidemiology: about 1 in every 200 live births.About 1/5 of cases are multiple.
Sites of location: infantile hemangioma may be located on any body surface but is most common in the region of the head and neck, particulary the parotid, where follows distribution of cutaneous nerves and arteries.
Clinical findings: during early stage may resemble a common birthmark in that it is a flat, red lesion that intensifies in color when infant strains or cries. With time bocome elevated with protruding appearance that distinguished it from birthmarks and sometimes is called strawberry nevus. They appear within a few weeks after birth and rapidly enlarge over a period of several months, achieving the largest size in about 6-12 months; they regress over the period of a few years. Regression show changes from scarlet to dull grey-red and wrinkling of the skin. It has been estimated that by age 7 years, 75-90% of cases involuted, leaving small pigmented scar.
Histopathology: the tumor forms multinodular mass fed by a single normally occuring arteriole. Histological features varies with its age. Early lesions are characterized by plump endothelial cells that line vascular spaces with small inconspicuous lumens. Mitotic figures may be found. Mast cells may be present. As the lesion mature and blod flow through the lesion commences, the endothelium becomes flattened and resembles adult form of capillary hemangioma. Maturation usually begins at the periphery of the tumors but ultimately involves all zones. Regression is accompanied by a progressive, diffuse interstitial fibrosis.
Immunohistochemistry: immunophenotypic profile correlates with clinical phases of infantile hemangioma:
proliferative phase (0-12 months) tumor cell express proliferative cell nuclear antigen (PCNA), VEGF, and type IV collagenase
involuting phase (1-5 years) CD31, vWF, GLUT1 (CD31 and vWF may be lost when lesion is fully involuted)
Prognosis: Treatment of these lesions must be individualized and depends on location and rate of growth. Large, life threatening lesions arising on critical organs (e.g. airways) are usually treated with glucocorticoids until a clinical response is achieved. It has been established that not complicated cases have involuted, 75-90% of cases at age 7 years.
Definition: rare, benign but clinically extensive vascular lesion of soft tissue occuring in infants.
Epidemiology: these lesions probably begin to grow during intrauterine life when the limb buds to form, grow proportionately with the fetus and involve large areas of extremities and trunk. Can occurs in newborn and infants (when occur in the first year of life is called diffuse neonatal angiomatosis)
Sites of involvement: involvement may be of two types:
1. extensive vertical involvement of multiple tissues (e.g., subcutis, muscle, and bone)
2. extensive involvement of tissue of the same type (e.g., multiple muscles).
Frequently affects the lower extremities and buttock but may occur throughout the body.
Clinical findings: usually symptoms of diffuse swelling, sometimes associated with pain and discoloration.
Imaging: CT scans appear as ill-defined nonhomogenous masses that may resemble sarcoma exept for presence of dense areas corresponding to thick-walled vessels.Large presence of fat may appear as fatty tumors.
Histopathology: histologically angiomatosis may show two patterns. The first and more common pattern show proliferation of vessels of different size, composed of large venous, cavernous, and capillary-sized vessels scattered in soft and fat tissue. The venous vessels are remarkable for their irregular, thick walls that have occasional attenuations and herniations. A rather characteristic features is the presence of small vessels clustered around the wall of large vein. The second pattern is identical to that of capillary hemangiomas, exept that the nodule of tumor diffusely infiltrate the surrounding soft tissue.The abundance of fat within angiomatosis has given rise to the alternative designation of "infiltrative angiolipoma".
Prognosis: nearly 90% of patients experienced recurrences, and 40% had more than one recurrence within 5-year period.
LYMPHANGIOMA
Definition: a benign, cavernous/cystic vascular lesion composed of dilated lymphatic channels.
Epidemiology: lymphangiomas are common pediatric lesions, most often present at birth or during first year of life. Some cases may identified in Turners syndrome ( monosomy chromosome X, 46 X) and may be found in abortuses. Cavernous/cystic lymphangioma of head and neck represents the most common type and is also called cystic hygroma.
Sites of involvement: cystic lymphangiomas are mostly located in the neck, axilla and groin. Cavernous type occurs additionally in the oral cavity, upper trunk, limbs and abdominal sites including mesentery and retroperitoneum.
Clinical features: the lesions rather present as circumscribed painless swelling, which are soft and fluctuant in palpation, and can show displacement surrounding organs at mediastinal or abdominal sites.
Imaging: USG show cystic nature, angiography show poor vascularization and CT scan reveals multiple, homogenous, nonenhancing areas.
Gross: lymphangiomas vary from well-circumscrbed lesions made up of one or more large interconnecting cysts to ill-defined, sponge-like compressible lesion composed of microscopic cysts. The former were traditionally termed as cystic lymphangiomas (cystic hygroma) and the latter as cavernous hemangioma.
Histopathology: cavernous lymphangiomas are characterized by thin-walled, dilated lymphatic vessels of different size, which are lined by a flatened endothelium and frequently surrounded by lymphocytic aggregates. The lumina may be either empty or contain proteinaceous fluid, lymphocytes and sometimes erythrocytes. Larger vessels can be invested by a smooth muscle layer, and long standing lesions may show fibrosis and inflammatory changes. Stromal mast cells are common and hemosiderin deposition is frequently seen.
Immunohistochemistry: positive for lymphatic lineage markers D2-40, VEGFR 3.
Prognosis: recurrences are due to incomplete surgical removal, whereas malignat transformation does not occur. Lymphangiomas of neck/axilla may extend to mediastinum and may compromise trachea, esophagus.
Definition: lipomatosis of nerve is characterized by infiltration of the epineurium by adipose and fibrous tissue. The tissue grows between and around nerve bundles causing enlargement of involved nerve.
Epidemiology: frquently first noted at birth or in early childhood. In the largest reported series patients ranged in ages 11 to 39 y/o. In some cases it is associated with macrodactyly of the digits inervated by the affected nerve. Females predominate when lipofibroma is accompanied by macrodactyly, whereas males are more commonly affected when macrodactyly is absent.
Sites of involvement: the medial nerve and its digital branches are most commonly affected followed by the ulnar nerve.
Clinical features: presents with a gradually enlarged mass in the affected area that may be asymptomatic or associated with motor or sensory deficits. Patients with macrodactyly have symmetrical or assymetrical enlargementf of affected finger(s) with enlargement of the involved bones.
Imaging: fat around fascicles of enlarged nerve (usually median)
Gross: grossly there is fusiform enlargement of the nerve by yellow fibrofatty tissue, which is generally confined within the epineural sheath.
Histopathology: the epineurial and perineurial compartments of enlarged nerve are infiltrated by mature adipose tissue which dissects and separate nerve bundles. Concentric perineural fibrosis is additional prominent feature. The affected nerve may also show other changes as perineural septation, microfascicle formation and pseudoonion bulb formation mimicking an intraneural perineurioma.
Prognosis: lipomatosis is benign lesion with no effective therapy. Surgical excision usually causes severe damage of the involved nerve. Division of the transverse carpal ligament may relieve neurological symptoms.
Definition: a well-demarcated intraneural or diffusely infiltrative extraneural tumor consisting of mixture of cell types, including Schwann cells, perineural-like cells, and fibroblasts; multiple and plexiform neurofibromas are typically associated with neurofibromatosis type 1.
Epidemiology: neurofibromas are common and occur either as sporadic solitary nodules unrelated to any apparent syndrome or as solitary, multiple or numerous lesions in individuals with neurofibromatosis type 1 (NF1 loss of 17q gene region). All ages and both sexes are affected.
Sites of involvement: neurofibroma presents most commonly as a cutaneous nodule (localized cutaneous neurofibroma) and less often as a circumscribed mass in a peripheral nerve (localized intraneural neurofibroma) or as a plexiform enlargement of a plexus or major nerve trunk.
Clinical features: rarely painful, the tumors present as a mass. The presence of multiple neurofibromas is the hallmark of NF1, in which they are associated with pigmented cutaneous macules (cafe-au-lait spots) as well as 'freckling', often axillary in location.
Gross: cutaneous neurofibromas are either nodular to polypoid and rather circumscribed, or are diffuse and involve skin and subcutaneous tissue. On cut surface, both are firm, glistening and grey-tan. Plexiform neurofibromas consist of either multinodular tangles ("bag of warms") when tumor involves multiple trunks of a plexus or rope-like lesions when multiple fascicles of a large, non-branching nerve such as the sciatic are affected.
Histopathology: neurofibromas are composed of schwann cells with ovoid to thin, curved to elongated nuclei and scant cytoplasm as well as fibroblasts in a matrix of collagen fibers and Alcian blue-positive, myxoid material. The schwann cells are considerably smaller than those of schwannomas. Neurofibromas may show numerous atypical nuclei (atypical neurofibroma) or significantly increased cellularity (cellular neurofibroma). Even in the latter mitotic figures are rare. Stromal collagen formation varies in abundance and sometimes looks like dense, retractile bundles resembling "shredded carrots". Growth of neurofibroma cells is intially along the course of nerve fibers, which become enmeshed by tumor. When neurofibroma arising from medium or large size nerve, often remain confined to the nerve and encompassed by it thickening epineurium. In contrast, tumors arisisng in small nerves often spread diffusely into the surrounding dermis and soft tissue. Unlike schwannomas blood vessels in neurofibromas generally lack hyalinization.
Prognosis: plexiform neurofibromas and neurofibromas of major nerves are considered a precursor lesion to the majority of malignant peripheral nerve sheath tumors. Malignant transformation occurs in 5% of sizable plexiform tumors, but is rare event in diffuse cutaneous and massive soft tissue neurofibromas. Patients with large neurofibromas are highly likely associated with NF1 and should be investigated for other evidence of the disorder.
Definition: also known as nerve sheath myxoma, dermal nerve sheath myxoma
Epidemiology: usually arise in childhood and early adult life.
Sites of involvememt: situated in the dermis and subcutis and rare in deep soft tissue. Neurothecomas have predilection for upper portion of the body, such as the head, neck, and shoulder.
Clinical findings: subcutaneous nodule.
Histopathology: neurothecoma has a distinctive compartmentalized appearance due to fibrous bands divinding lesion into irregular lobules. Each lobule consists of variable mixture of cells and myxoid stroma, so tumor may appear myxoid or solid. The cells vary from round to spindled and typically have little atypia or mitotic activity. Giant cells are occasionally present in the lobules, and rarely neurites are identified among the tumor cells. Although most of the cases are myxoid, there are some more cellular, with marked cellular atypia, rare mitoses and extension to adjacent soft tissue ( cellular neurothecoma), which may be mistaken for sarcoma. The most helpful clues to recognize neurothecoma with atypical features are the superficial dermal location and the distinctive septate architecture.
Immunohistochemistry: tumor cells positive for S100 and PGP9.5.
Prognosis: benign neural tumor cured with excision.
Definition: pediatric, benign, poorly circumscribed, superficial soft tissue mass with three components: dense fibrocollagenous tissue,loosely textured areas of immature rounded mesenchymal cells and mature fat.
Epidemiology: accounting for 0.02% of all benign soft tissue, although is one of the relatively more common tumors of fibrous tissue in early childhood.
Sites of involvement: occurs most frequently in the anterior or posterior axillary fold, followed by the upper arm and shoulder, thigh, groin, back, and forearm. Rarely arises in the hands and feet.
Clinical features: the majority of fibrous hamartomas of infancy present in the first 2 years of life and up to 25% are discovered at birth. They do not occur after puberty, and there is boy predominance. Fibrous hamartoma of infancy is almost always a solitary lesion, rapidly growing, freely movable mass in the subcutis or dermis, occasionally attached to underlying fascia and rarely involving skeletal muscle.
Gross: usually poorly circumscribed, grey-white tissue alternating with yellow fat. Most lesions are less than 5 cm in diameter, tumors rarely reach larger than 10 cm.
Histopathology: characterized by three distinct components forming organoid structures. The well defined intersecting trabeculae of dense fibrocollagenous tissue are composed of fibroblastic and myofibroblastic spindle cells with bland, straight or wavy nuclei separated by varying amounts of collagen. Between fibrous trabeculae are islands of immature-appearing , small, rounded or stellate, primitive mesenchymal cells with scant cytoplasm embedded in myxoid matrix containing abundant hyaluronidase-sensitive acid mucopolysaccharides. The primitive myxoid areas are frequently oriented around small veins. The mature fat component is interspersed among the other two components. The relative proportions of these components vary between cases.
Prognosis: fibrous hamartoma of infancy is benign and usually cured by local excision. Rare recurrences are cured by reexcision.
INFANTILE DIGITAL FIBROMATOSIS (INCLUSION BODY FIBROMATOSIS)
Definition:a benign proliferation of fibroblastic and myofibroblastic cells that typically occur on the digits of young children. It is named for the intracytoplasmic round inclusions staining red with trichrome.
Epidemiology: rare lesion on the digits of young children.
Sites of involvement: typically, lesion develop on the dorsal aspect of digits of the hands and feet. More than one digit involvement is less common. Involvement of the thumb or big toe is extremely unusual. Rarely infantile digital fibromatosis may occur in extra-digital sites such as the soft tissue of the arm or breast.
Clinical features: patients typically present in the first year of life. There is no sex predilection. The nodule on the digit usually measures less than 2.0 cm and the overlying skin is typically taught and strched.
Gross: the lesion have a uniform white/tan appearance. They are typically ill defined.
Histopathology: the nodules are composed of intradermal sheets and fascicles of uniform spindle cells associated with varying amounts of extracellular collagen. They are non-encapsulated and ill defined with extension to adjacent soft tissue. Individual cells have central elongated nuclei and vaguely fibrillar cytoplasm. The diagnostic feature is presence intracytoplasmic round to spherical eosinophilic "inclusion". Inclusions are brightly red trichrome positive and PAS negative. These are present in minority of cells and are not always uniformly distributed. The lesional cells lack nuclear atypia and there are no prominent mitoses present.
Prognosis: local recurrence occurs in about 50% of cases. The main prognostic indicator is margin free primary excision. Metastasis does not occur.
Definition: myofibroma (solitary) and myofibromatosis (multicentric) is benign neoplasm composed of contractile myoid cells arranged around thin-walled vessels. Myofibroma(tosis) forms a morphological continuum with myopericytoma and so-called infantile hemangiopericytoma.
Epidemiology: may occur from newborn to elderly, however many cases are diagnosed at birth or within the first two years of life. Myofibroma(tosis) is more common in males.The relative frequency of solitary versus multicentric forms in unclear. In adults, solitary lesions are more common.
Sites of involvement: 50% of solitary myofibromas occur in the cutaneous/subcutaneous tissues of head and neck region, followed by trunk, lower and upper extremities. The other 50% occur in skeletal muscle or aponeuroses, with a small number involving bone, predominantly the skull. Myofibromatosis (multicentric) involves both soft tissue and bone and frequently (10-20%) occurs in the deep soft tissue and visceral location.
Clinical features: lesions may be of short or long standing duration. Cutaneous lesions have the appearance of purplish macules, simulating vascular neoplasm. Subcutaneous lesions occur most often as painless, freely movable masses while more deeply seated lesions may be fixed. Visceral lesions may cause symptoms referable to the organs that are involved.
Imaging: soft tissue lesions varies, and can be well-circumscribed or infiltrative, often with calcifications, either within or surrounding the lesion. Bony lesions characteristically occur as multiple elongated radiolucent lesions within the metaphyseal regions, spering the region adjacent to epiphysis.
Gross: nodules vary in size from 0.5 - 7.0 cm. Lesion in cutaneous or subcutaneous tissue are better defined than those in deep soft tissue.On cut surface have a firm surface, greyish-white, light-tan to brown. They often have central yellow (necrotic) areas or cystic spaces filled with caseous-like material or hemorrhage.
Histopathology: at low power show nodular or multinodular proliferation with zonation. Usually within periphery of the nodules, there are plump myofibroblasts arranged in short fascicles or whorls. Myofibroblasts are spindle shapedwith pale pink cytoplasm and have elongated, tapering nuclei with vesicular chromatin pattern and one or two nuclei. There is no significant atypia or pleomorphism. Within the center of the lesion, cells are less well differentiated, they are round, polygonal or spindle cells with slightly larger hyperchromatic nuclei. These cells have scant cytoplasm, and are arranged around thin-walled, irregulary branching, hemangipericytoma-like vessels. The hemangiopericytoma-like component can predominate. Calcification, necrosis and stromal hyalinization are identified frequently. Mitotic activity is usually minimal.
Immunohistochemistry: tumor cells positive for vimentin and actin and negative for S100.
Prognosis: some myofibromas regress spontaneously. A small number (<10%) recur, but there are not specific factors suggesting
recurrence and reexcision in most of the cases is curative. The extent and location of the visceral lesions determines the prognosis, with involvement of vital organs, leading to cardiopulmonary or gastrointestinal complication, causing death in rare cases. Pulmonary involvement appears to be especially bad prognostic factor.
Definition: benign disorder characterized by the accumulation of extracellular "hyaline material" within skin, somatic soft tissues and the skeleton mimicking tumor like masses, and typically presents in infancy.
Epidemiology: juvenile hyaline fibromatosis is rare disorder. There is no sex predilection and affected infants are often the progeny of affected parents. Most of the time there is progressive increase in the number and size of superficial and deep nodules with resulting deformity and dysfunction.
Sites of involvement: the tumor-like masses of hyaline material develop in the skin (particulary the face and neck resulting in papules and nodules), gums (causing gingival hyperplasia), periarticular soft tissue (resulting in joint contractures) and bones (especially the skull, long bones and phalanges).
Clinical features: patients present with skin papules affecting the face and neck, in particular around the ears. Perianal papules may resemble genital warts. Periarticular deposit of hyaline material may cause joint contracures, most commonly involving knees and elbows.
Imaging: imaging studies of affected bones reveal generalized osteoporosis and discrete lytic lesions.
Histopathology: individual nodules obliterate normal tissue. They are composed of an admixture of plump fibroblastic cells associated with extracellular uniform hyaline material (produced by fibroblasts) that is non-fibrillar and eosinophilic in H&E stain. In younger patients or new lesions the nodules are relatively more cellular. The fibroblasts have clear cytoplasm and may exhibit a vague fascicular arrangement. Nuclear atypia or necrosis is not seen. Older lesions are less cellular and the fibroblasts may appear compressed. PAS is strongly positive and diastase resistant.
Prognosis: the lesions are treated by surgical excision depending on their location. Local recurrences are high. The prognosis depends on number, size and location of nodules and the patient's functional impairement.
Definition: a benign, site-specific lesion that occurs in the distal sternocleidomastoid muscle of infants. The mass results in fusiform thickening of the muscle and cervicofascial assymetry due to its shortening (torticollis).
Epidemiology: uncommon, occurs in about 0.4% of live births. There is nosex predilection. The majority of cases are diagnosed before 6 months of age.
Sites of involvement: typically affects the lower one third of the sternocleidomastoid muscle.
Clinical features: the affected infants present with a smooth fusiform swelling of the distal sternocleidomastoid muscle.
Imaging: uniform isoechoic mass confined to muscle.
Gross: lesion appears as tan gritty mass confined to the muscle.
Histopathology: low cellularity, collagen rich-tissue that resembles scar or conventional fibroma. The lesion is composed of uniform plump fibroblastic and myofibroblastic cells embedded in rich collagen.Infiltration and entrapment of skeletal myocytes is evident.
Prognosis: when diagnosed early is managed in non-surgical manner. The treatment involves passive streching and physiotherapy. 70% of patients will have complete resolution of mass and demonstrate normal cervico-fascial posture and movement with this approach. Surgical intervention, principally tenotomy, is required in 10-15% of patients. The worse prognosis is in patients diagnosed and treated when older than 1 year.
Definition: benignfibrofatty tumor of childhood with predilection for distal extremities.
Clinical features: ill defined, slowly growing, painless mass in hands and feet and rarely occurs in the thigh, trunk and head. The tumor has been described exclusively in children. The madian age for surgery is 1 year. Male:female ratio 2:1.
Gross: the lesion usually is yellowish or whitish-tan, with fatty componenet, usually measuring 1-3 cm.
Histopathology: infantile fibromatosis has a wide morphologic spectrum reflecting progressive stages in the differentiation of the fibroblasts. The more common form of infantile fibromatosis is the diffuse (mesenchymal) type. This form is usually found in infants in first few months of life and is characterized by small, haphazardly arranged, round or oval cells deposited in a myxoid background. The cells are intermediate in appearance between primitive mesenchymal cells and fibroblasts and they are intimately associated with residual muscle fibers and lipocytes. Some cases have extensive lipocytic elemts, and is reffered as lipofibromatosis. Peripherally located lymphocytic inflammation is often present. Sometimes tumor may be highly cellular and mitotically active, making distinction from infantile fibrosarcoma difficult. The less common form of infantile fibromatosis (desmoid type) is virtually indistinguishable from the adult form of fibromatosis (desmoid tumor). This type usually occurs in children older than 5 years of age and behaves like adult desmoid tumor. Although the morphology is similar to aduilt lesion, calcification and/or ossification is a feature peculiar to pediatric cases.
Immunohistochemistry: spindle cells are often focally positive for CD34, BCL2, S100, actins and EMA.
Prognosis: the tumor has a high rate of nondestructive local recurrence, but no metastatic potential.
Definition: inflammatory fibroblastic tumor (IMT) is a histologically distinctive lesion composed of myofibroblastic spindle cells accompanied by infiltrative inflammatory component of plasma cells, lymphocytes and eosinophils. It occurs primarily in soft tissue and viscera of children and young adults.
Epidemiology: IMT is primarily soft tissue and visceral tumor of children and young adults. The mean age is 10 years,and the median is 9 years. There is slight female predominance. The finding of human herpervirus-8 DNA sequences were reported, although no exact etiology is known.
Sites of involvement: IMT can occur throughout the body, and the most common sites are the lung, mesentery, and omentum.
Clinical findings: The site of origin determine the symptoms of IMT. Pulmonary IMT may cause chest pain and dyspnoea, but may be asymptomatic. Adbominal tumors may cause gastrointestinal obstruction. In up to 1/3 of the patients, a clinical syndrome occur with fever, growth failure, malaise, weight loss, anemia, and elevated erythrocyte sedimentation rate. When the mass is exised, the syndrome disappears, and it reapperance may be sign of recurrence.
Imaging: lobulated solid mass, which may be inhomogenous. Calcifications are sometimes detectable.
Gross: circumscribed or multinodular firm, white or tan mass with a whorled fleshy or myxoid cut surface. Focal hemorrhage, necrosis, and calcification are seen in minority of cases.
Histopathology: the spindled myofibroblasts, fibroblasts and inflammatory cells form three basic histological patterns of IMT. Firts pattern show loosely arranged plump or spindled myofibroblasts in an oedematous myxoid background with abundant blood vessels and an infiltrate of plasma cells, lymphocytes and eosinophils resemble granulation tissue, nodular fasciitis, or other reactive processes. A second pattern is characterized by a compact fascicular spindle cell proliferation with variable myxoid and collagenized regions and a distinctive inflammatory infiltrate with diffuse inflammation, small aggregates of plasma cells or lymphoid nodules. This resembles a fibromatosis, fibrous histiocytoma, or a smooth muscle neoplasm. In some instances, the spindled myofibroblastic cells surround blood vessels or bulge into vascular spaces, similar to infantile fibromatosis or intravascular fasciitis. Ganglion-like myofibroblasts with vesicular nuclei, eosinophilic nucleoli, and abundant ampophilic cytoplasm are often seen these two patterns. The third pattern resembles a scar or desmoid type fibromatosis, with pale-like collagen, lower cellularity, and relatively sparse inflammation with plasma cells and eosinophils. Coarse or psammomatous calcifications and osseous metaplasia are occasionally seen.
Immunohistochemistry: positive for ALK (Anaplastic lymphoma kinase) and SMA (smooth muscle actin).
Genetics: IMT contain clonal cytogenetic rearrangements that activate the ALK receptor tyrosine kinase gene in chromosome band 2p23.
Prognosis: IMT has recurrence rate of approximately 25% related to location, resectability and multinodualrity. Although surgery is the principal treatment, regression and response to corticosteroids and nonsteroidal inflammatory agents have been noted in rare cases.
Definition: benign tumor of the palms and soles of children with propensity for local recurrence. Fici of calcification, palisaded round cells and fibroblasts are characteristic for this lesion.
Epidemiology: CAF is very rare. The age range spans 0-64 with a median age of 12 y/o. A slight male predisposition.
Sites of involvement: palms, soles, wrists and ankles are typical sites of involvement. CAF arises nesr tendons, fascia and aponeuroses.
Clinical features: CAF presents as a solitary, small, slowly growing, poorly circumscribed non-tender mass.
Gross: firm, pale, infiltrative mass, usually<3cm, with grity cut surface.
Histopathology: the typical lesion have twoo components.
1) nodular deposits of calcification, each surrounded by a palisade of rounded, chondrocyte-like cells, arranged in short, parallel arrays
2) a less cellular spindled, fibroblastic component between the coalescent calcified nodules emanating into the surrounding soft tissue.
The stroma of nodules is usually hyalinized but may have chondroid features. Osteoclastic giant cells may border the calcium.
Immunophenotype: positive for vimentin,smooth muscle actin, CD99 and S100.
Prognosis: about 50% of cases have local recurrence, usually within 3 years of diagnosis. Local recurrence is more likely in patients <5 y/o but the likelihood of recurrence is not predictable on the basis of morphology, location or the completeness of the primary excision.
Definition: rare benign fibrous lesion affecting children and young adults. It is paucicellular, with fibroblasts, dense collagenization, psammomatous and dystrophic calcification, and patchy lymphoplasmacytic infiltrates.
Epidemiology: most soft tissue examples affect children and young adults without gender predilection.
Sites of involvement: originally described in the subcutaneous and deep soft tissues (extremity, trunk, neck and scrotum) but have been reported all over the body.
Clinical features: soft tissue painless masses. Visceral examples may produce site-specific symptoms.
Imaging: radiographs show well marginated, noncalcified tumor. CT show apparent calcifications and may be thick, band-like or punctate. On MRI masses appear similar to fibromatoses, with a mottled appearance and a signal closer to that of muscle than fat.
Gross: tumors are well marginated but unencapsulated, ranging in size from <1 to 15 cm.
Histopathology: tumor is most of the time well circumscribed, unencapsulated, paucicellular, hyalinized fibrosclerotic tissue with a variable inflammatory infiltrate consisting of lymphocytes and plasma cells. Lymphoid aggregates may be present. Calcifications, both psammomatous and dystrophic, are scattered throughout.
Immunophenotype: lesional cells are positive for vimentn and factor XIIIa.
Definition: a benign neoplasm composed of mixture of fibroblastic and histiocytic cells arranged in sheets of short fascicles and accompanied by inflammatory cells, foam cells and siderophages, which may develop within subcutaneous tissue, deep soft tissue or in parenchymal organs.
When located in skin is also called dermatofibroma.
Epidemiology: deep BFH are rare and may be misdaignosed with solitary fibrous tumor. More common is dermatofibroma. May occur in any age, but most affect adults over 25 y/o.
Sites of involvement: the lower limb and the head and neck region are the most common sites. Most cases involve subcutaneous tissue, but a few cases were described in muscle, mesentery, trachea and kidney.
Clinical features: most cases present as cutaneous, solitary pailess and slowly enlarging mass. A subset occurs following minor trauma or insect bite.
Gross: cutaneous BFH are elevated or pedunculated lesions measuring from a few milimeters to few centimeters.
Histopathology: cutaneous FH consist of nodular spindkle cell proliferation involving dermis and occasionally subcutis. The tumor is sharply demarcated laterally and typically interdigitates with dermal collagen ("collagen traping"). the tumor cells are cytologically bland and generally spndle shaped with elongated or plump vesicular nuclei and eosinophilic, ill defined cytoplasm. There is no nuclear pleomorphism, hyperchromasia, and mitosees may be common but usually less than 5 per 10 HPF. The stroma may show myxoid change or hyalinization and some xanthoma like cells. Deep fibrou histiocytoma usually is similar to cutaneous form, but show more prominent storiform pattern and fewer secondary elements like xanthoma cells.
Definition: benign histiocytic subcutaneous lesion that usually occurs during childhood.
Epidemiology: the lesion usually develop during infancy and is charactarized by one or more cutaneous nodules and less often by additional lesions in deep soft tissue or organs. As a rule, those that develop after the age of 2 years or in adults are usually solitary.
Clinical findings: about 50% of lesions develop on the head and neck, followed by the trunck and extremities. They measure from few milimeters to few centimeters. The early lesions present as red papules, and the older lesions are brown or yellow. In the less common form of the disease, cutaneous lesions may be accompanied by similar lesions in other sites, such as the eye, lung, epicardium, oral cavity or testis.
Histopathology: JX lesions are composed of sheets of histiocytes involving the dermis and extending to, but not invading, the flattened epidermis. The infiltrate closely approaches adnexal structures and extends into subcutis. Deeply situated JX appear circumscribed but blend with or infiltrate muscle at the periphery. Histiocytes are well differentiated and exhibit little or no pleomorphism with rare mitoses. Early lesions may show some lipid features. In older lesions the cells have a finely vacuolated or even xanthomatous cytoplasm. Giant cells, including Touton giant cells are typical for this lesion. Usually additional components of inflammatory cells are present, including lymphocytes, neutrophils, and eosinophils. Long standing lesions may develop interstitial fibrosis, even storiform pattern resembling conventional fibrous histiocytoma seen in adults.
Imunohistochemistry: tumor cells are positive for CD68, alpha1 antitrypsin, lysozyme, CD31 and factor XIIIa and negative for CD1a and S100.
Prognosis: the skin lesion usually regress or at least stabilize with time, and even large , deeply localized lesions pursue a favorable course.
Definition: painless nodule or mass in subcutis with the predilection for the back otf the thigh, inguinal region and chest wall in children younger than 5 years of age.
Epidemiology: 2/3 of the children were younger than 5 y/o when brought to medical attention, and the median age was 3 y/o. Male predominant (75%).
Clinical findings: painless nodule or mass in dermis or subcutis, with predilection for the back of the thigh, inguinal region, and chest wall.
Gross: grey to yellow mucoid masses that are poorly circumscribed and measure 1-8 cm.
Histopathology: composed of loosly arranged, wavy spindle cells with moderate degree of nuclear pleomorphism that infiltrate the deep dermis and subcutis and encircle adnexal structures in fasion similar to dermatofibrosarcoma protuberans. The tumors vary in cellularity from cellular resembling dermatofibrosarcoma protuberans to those that are hypocellular with a myxoid or hyaline stroma. The characteristic feature of tumor are pseudovascular spaces lined by giant cells.
Immunohistochemistry: positive for vimentin and some giant cells may express CD34, negative for S 100 and vascular markers.
Prognosis: may recur in 50% of cases, especially if not exised completely.
Definition: slowly growing plexiform fibrohistiocytic neoplasm of the deep dermis, occurs almost exclusively in children and young adults.
Epidemiology: slowly growing mass of the deep dermis and subcutaneous tissue, occuring almost exclusively in children and young adults.
Sites of involvement: the most common location is the upper extremity (63%) followed by the lower extremity (14%).
Clinical features: typical slow growing mass in deep dermis and subcutis.
Gross: relatively small (1-3 cm), ill-defined masses with a gray-white trabecular appearance.
Histopathology: typical form shows two components: a differentiated fibroblastic component and a round cell histiocytic component containing multinucleated cells. At low power microscopy you can see numerous tiny cellular nodules that occupy the dermis and subcutaneous tissue. These nodules are composed of nests of histiocytic cells that often contain multinucleated, osteoclast-like giant cells and occasionally undergo focal hemorrhage. The cells in nodules are well differentiated and do not express atypia or increased mitotic level. The nodules are circumscribed by short fascicles of fibroblastic cells that intersect slightly or ramify in the soft tissue, creating a plexiform growth pattern. The fascicles of fibroblastic cells may resemble fibromatosis, exept that the cells are usually plumper and the fascicles shorter than those of fibromatosis.
Immunohistochemistry: CD68 positive in giant cells and mononuclear cells, smooth muscle actin is positive in spindle cells.
Prognosis: these tumors appear to be low-grade neoplasm with recurrence 12-40% within 1-2 years of the original diagnosis and excision.
Definition: rare benign mesenchymal tumor that show immature skeletal muscle differentiation and predilection for the head and neck in children.
Sites of involvement: more than 90% of fetal rhabdomyomas occurs in the soft tissue or mucosal sites of the head and neck (most common postauricular site).
Clinical features: most pateints < 1 year old (medain age 4 y/o). Male to female ratio M:F 2.4:1. The median size is 3 cm. Mostly present as well defined solitary superficial mass involving soft tissue or mucosa of head and neck.
Gross: solitary, circumscribed, soft, grey-white to tan-pink mass with glistening cut surface.
Histopathology: Two closely related types can be distinguished by microscopy. The myxoid classic type is composed of primitive oval or spindle-shaped cells with indistinct cytoplasm, interspersed immature skeletal muscle fibers reminiscent to fetal myotubes seen during the seventh to tenth weeks of intrauterine life, in rich myxoid stroma. The immature skeletal muscle cells have small uniform nuclei with delicate chromatin and inconspicuous nucleoli with bipolar or sometimes unipolar, eosinophilic cytoplasm. Cross striations are rare and difficult to identified. The intermediate cellular type is characterized by the presence of numerous differentiated muscle fibers, less conspicuous or absent spindle-shaped mesenchymal cells, and little or no myxoid stroma. The predominant cells are strap-shaped muscle cells with abundand eosinophilic cytoplasm, centrally located vesicular nuclei, and frequent cross-striations reminiscent of the cells seen in adult rhabdomyomas; many of the cells contain glycogen and are often vacuolated. Others have prominent ganglion-like rhabdomyoblasts with large vesicular nucleai and prominent nucleoli. In some cases there is mild cellular pleomorphism, but marked cellular atypia is not seen. Transitional forms of myxoid and intermediate types are not rare and in fact age and duration may play a role.
Immunophenotype: skeletal muscle cells positive for myoglobin, desmin and smooth muscle antigen.
Genetics: multiple cases of fetal rhabdomyoma have been reported in patients with nevoid basal cell carcinoma syndrome.
Definition: a lobulated, localized (lipoblastoma) or diffuse(lipoblastomatosis) tumor, resembling fetal adipose tissue.
Epidemiology: both types of tumor are most commonly found in the first three years of life. They may occasionally be found at birth or in older children. There is male predilection.
Sites of involvement: The extremities are most common location but location in mediastinum, retroperitoneum and head and neck areas was described.
Clinical features: most patients present with slow growing soft tissue nodule/mass, well circumscribed and confined to the subcutis in case of lipoblastoma , infiltrating deeper muscle in case of lipoblastomatosis.
Gross: relatively small lesions (2-5 cm), showing fatty looking tissue with gelatinous areas.
Histopathology: lipoblastoma shows lobulated architecture with an admixture of mature and immature adipocytes, the latter corresponding to lipoblasts in various stages of development. Depending of age of the patient, the lipoblast may be very scarse and lesion may be dominated by lipoma-like component (mostly in older patients). Connective tissue septa separate lobules. The lobulation is less prominent in lipoblastomatosis. The matrix can be quite myxoid, with a plexiform vascular pattern, thus mimicking myxoid liposarcoma. Occasionally lipoblastoma(tosis) may show extramedulary hematopoiesis or cells resembling brown fat. Cellular maturation has been described, leading to lipoma-like picture.
Genetics: characteristic cytogenetic feature is rearrangement of 8q11-13, which has been found in majority of cases.
Prognosis: lipoblastoma is benign and malignant transformation or metastatsis does not occur. Recurrences are described in 9-22% of cases mainly in lipoblastomatosis.
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