Epithelioid sarcoma, first described by Enzinger in 1970 [1, 2], is a rare soft tissue sarcoma of adolescents and young adults usually involving the distal part of upper extremities [1, 2]. The epithelioid sarcomas are difficult to diagnose and can be confused with a variety of malignant and benign conditions; especially granulomatous process, synovial sarcoma and ulcerating squamous cell carcinoma [2]. This is usually a slow growing tumour which commonly involves the dermal or subcutaneous area of distal part of upper extremities. Sometimes it can be deeply seated attached to tendons, tendon sheaths or fascial structures [4]. The “proximal type or axial type” variant was later recognized in 1997 [2], with very few reports on such cases. It is usually seen in adults and are commonly deep seated and occurs in perineum, sex organs, pelvis and thighs. It is more aggressive with poorer prognosis with tendency for local recurrence and early metastases. The proximal type epithelioid sarcomas are rare undifferentiated soft tissue sarcomas usually seen in adults with epithelioid features and a frequent rhabdoid phenotype on histopathology [1] thus posing diagnostic difficulty and has to be differentiated from extrarenal rhabdoid tumour, synovial sarcoma, angiosarcoma and melanoma [1, 5] (Figs. 1, ,2,2, and and33). Fig. 1 (a & b): Ultrasound and colour Doppler images showing the mass(white arrow), femoral vessels (thin white arrow) in relation to the lesion Fig. 2 (a, b, c & d): CT scan images showing the mass as slightly hypodense to adjacent skeletal muscle(white arrow). Neurovascular bundle in close proximity to the lesion. The mass shows mild enhancement in post contrast scan (fig b). Coronal reformation ... Fig. 3 PhotoMicrograph(H&Ex 400) showing densely cellular sheets and nests of moderately pleomorphic predominantly polygonal to epithelioid cells with vesicular to hyperchromatic mitotically active nuclei and moderate amount of eosinophilic to clear ... Case Report A 5 year old boy presented with painless swelling in the posterior aspect of the right thigh of 1 month duration. There was no history of trauma, fever or weight loss. On local examination a well defined swelling measuring approximately 8 × 6 cms was noted in the posterior aspect of the middle one-third of the thigh. The swelling was non-tender, firm, non-mobile and not associated with local signs of inflammation. Skin over the lesion was pinchable. Radiograph of the right thigh was done which showed focal soft tissue swelling in the mid thigh posteriorly but no focus of calcification was identified. The femur was normal. Ultrasonogram of thigh was done in GE Voluson Pro using 11 Mhz probe which revealed a well circumscribed isoechoic mass in posterior aspect of thigh. Colour Doppler showed mild internal vascularity within the lesion. Contrast enhanced CT scan of thigh was performed in Asteion Toshiba CT scanner. Non contrast CT scan showed a well circumscribed homogenous oval mass measuring 30 × 38 × 45 mm which was slightly hypodense to adjacent skeletal muscles with HU of 50. No calcification was seen in this lesion. The lesion was in intermuscular plane between the posterior compartment and medial compartment of thigh. The lesion was closely abutting and indenting the adjacent muscles i.e. biceps femoris, semimembranosus and semitendinosus muscles laterally and adductor magnus muscle medially. In post contrast CT scan there was mild heterogeneous enhancement of the lesion. A few small areas of necrosis were seen in inferior part of the lesion. The lesion was closely abutting the femoral vessels but not encasing it. The lesion was in close proximity to the sciatic nerve. The femur was normal. The possibility of soft tissue sarcoma of thigh probably rhabdomyosarcoma was considered. To rule out metastatic foci, radiograph of chest, contrast enhanced CT scan of chest, abdomen and pelvis were done, which were normal. No metastatic foci were identified. Bone marrow biopsy was also done which was also normal. Since no distant metastases was seen, the patient was an ideal candidate for surgery. The patient underwent wide local excision of the tumour with resection of adjacent margins. The lesion was well encapsulated and measured 6.5 × 4 × 3 cms. There was no perineural invasion or muscular infiltration. Histopathological examination revealed densely cellular non descript sheets and nests of moderately pleomorphic predominantly polygonal epithelioid cells with moderate anisonucleosis, vesicular to hyperchromatic mitotically active nuclei and moderate amount of eosinophilic to clear cytoplasm. Based on histopathological features, diagnosis of undifferentiated sarcoma was considered with possibilities of extrarenal malignant rhabdoid tumour or alveolar soft tissue sarcoma or solid variant of alveolar rhabdomyosarcoma. The tumour was high grade and undifferentiated with TNM stage pT2bNxMx. Immunochemistry revealed that the neoplastic cells are diffusely positive for cytokeratins, epithelial membrane antigen and vimentin and focally positive for synaptophysin and chromogranin. Negative for desmin and myo D. The final diagnosis after histopathology and immunohistochemistry was proximal- type epithelioid sarcoma of thigh.
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Jan 1, 2015
Vlamis John Karampinas K 
Open Access
