9Alveolar Soft part Sarcoma The most common sites:deep soft tissues of the thigh and leg.Most patients are young females.Gross:well circumscribed,usually large,moderately firm,gray or yellowish,area of necrosis and hemorrhage are common in larger tumors.This is a nested to alveolar proliferation of epithelioid cells which have eosinophilic granular cytoplasms.The nuclei are vesicular and show prominent nucleoli.Mitoses are exceptional.In children:more solid pattern of growthPAS positive-diastase resistant intracytoplasmic needle like structuresIHC:PAX8 (-),TFE3(diffusely +)
10Alveolar Soft Part Sarcoma Behavior & Prognosis: Slow and indolent clinical course but highly malignant.Vein invasion is common.Blood borne metastases in the lung or… can be seen lately after tumor excision.
11Alveolar soft part sarcoma Differential diagnosis: Renal cell carcinoma The absence of PAX8 immunoreactivity argues against this diagnosis.Granular cell tumors label diffusely for S100 protein, and should not show staining for TFE3 in a strong fashion in the majority of cases.Paraganglioma would label for neuroendocrine markers, and should not label for TFE3
12Mass of the foot (2.5 cm) in a 25 year old man. Case 2Mass of the foot (2.5 cm) in a 25 year old man.S100 stain was reactive
18Clear cell sarcoma Intimately associated with a tendon/aponeurosis . The most common site:feetMost of the patients are young adults,M>FGross:well crcumscribed,firm,gray or white,gritty sensation in cut sectionConsists of highly uniform cells arranged in nests and packets, punctuated by scattered giant cells.Most cells contain uniform enlarged nucleoli.Abundant extracellular and intracellular iron is present.Many tumor cells contain cytoplasmic melanin.IHC: The proliferating cells react with both S100 protein and HMB45 antibodies.
19Clear cell sarcomaClear cell sarcomas have been referred to as “malignant melanoma of soft parts” based on this immunophenotype.Differentiation from malignant melanoma:1) They have a specific translocation (t(12;22); EWS and ATF-1 fusion gene, in contrast to melanomas which have variably abnormal cytogenetic profiles)2) Their cytologic features are extremely monomorphic rather than pleomorphic3) They have different survival characteristics
20Clear cell sarcoma Differential diagnosis: 1)Malignant melanoma2) Tenosynovial giant cell tumor:. Tenosynovial giant cells occur in the fingers, typically, of middle-aged femalesTheir proliferating cells lack the prominent nucleoli found in clear cell sarcomas.Pigment found in clear cell sarcomas is melanin whereas that in tenosynovial giant cell tumors is hemosiderin.Tenosynovial giant cell tumors lack S100 protein and do not stain with HMB45 but, desmin is sometimes found in them.3) Schwannomas:Clear cell sarcomas express S100 protein, but the cells in schwannomas are more spindly and lack large nucleoli4) Epithelioid sarcomas :Occur in association with aponeuroses and tendon sheaths but they typically feature abundant necrosis and lack nucleoli. They express keratins and CD34 but not S100 protein.
21Case 3Posterior chest wall mass from a 87 year old man. There was no overlying ulcer.
28Atypical decubital fibroplasia/ishemic fasciitis This lesion is ill-definedZones of fibrinoid necrosis within fat lobules into which there is ingrowth of fibroblasts characterized by enlarged nuclei and macronucleoli, smudging of nuclear chromatin, and occasional mitoses.The overall cellularity is low.The proliferating nuclei are quite similar to those encountered in proliferative fasciitis (ganglion-like) but the overall lesion differs by having abundant necrosis
29Atypical decubital fibroplasia/ishemic fasciitis Occurs over bony prominences in bed-ridden (typically elderly) patientsCharacterized by tumefaction rather than ulceration .It is a benign presumably reactive lesions, although recurrences occasionally occur.
30Atypical decubital fibroplasia/ishemic fasciitis Differential diagnosis: 1)Well-differentiated liposarcoma: Atypical cells within fat but differs by having a zonated pattern, necrosis, and smudged degenerate nuclei rather than well-preserved malignant ones.2) Malignant fibrous histiocytoma:Differs by its overall low cellularity and zonation.
31Case 4Biopsy from a 3 cm paratesticular mass in a 3 year old boy. The lesion, at operation, was poorly marginated
37Fibrous hamartoma of infancy A tumorlike condition occure almost exclusively during the first 2 years of lifeM>FThe most common sites:shoulder,axilla,upper armThe"common less common" site is the genital region, resulting in a clinical impression of lymphadenopathy or rhabdomyosarcomaAlmost always solitaryGross:poorly circumscribed,whitish tissue of fibrous appearance with islands of fat
38Fibrous hamartoma of infancy Displays three components:A) Adipose tissue, some of which has tiny cytoplasmic droplets in keeping with brown fat.B)Haphazardly placed paucicellular fascicles of spindle cells with abundant collagen.C)Primitive-appearing rounded to spindled cells set in pale amphophilic stroma.There is no necrosis and mitoses are not identified.
39Fibrous hamartoma of infancy Differential diagnosis: 1)Rhabdomyosarcoma: Rhabdomyosarcomas are not triphhasic and feature mitotic activity and more impressive cytologic atypia.IHC of fibrous hamartoma of infancy:the paucicellular bands are actin(+),desmin(-). The primitive-appearing cells are immunohistochemically "inert" with muscle marker.IHC of Rhabdomyosarcomas :focal desmin(+) and MyoD1 or myogenin(nuclear +), although the latter has been reported in some myofibroblastic lesions in abstract form2) dedifferentiated liposarcoma :these are high grade sarcomas, usually of the retroperitoneum of older adults, featuring well-differentiated liposarcoma and juxtaposed high grade pleomorphic sarcoma
4023 year old man with thigh mass Case 523 year old man with thigh mass
47Mesenchymal chondrosarcoma About two thirds arise in bone and the remainder in soft tissue.In skeletal sites, the mandible, rib, pelvic bones, and femur are the most common sitesThe extraskeletal examples presented in lower extremities followed by the meninges.Most lesions present in the second and third decades of life.
48Mesenchymal chondrosarcoma Histologic features :"small round cells" with scant cytoplasm arranged around hemangiopericytoma-like vasculature and punctuated by islands of mature-appearing cartilage.Reticulin staining encloses small groups of cellsIHC:CD99(in the small cell component),S100(in the cartilaginous component),focal positivity for Actin,Desmin,Myogenin,NSEThe extracellular matrix contains type II Collagen(diagnostic)