Epithelioid sarcoma mimicking angiosarcoma: the value of immunohistochemistry in the differential diagnosis.

Epithelioid sarcoma (ES) is a rare malignant tumour of young adults, usually presenting as a skin ulcer or subcutaneous nodule in the distal portion of the upper limb. Multiple recurrences and late metastases are typical, leading to fatality in a third to one-half of all cases. The slow evolution of the tumour is one reason for its delayed recognition. The other is its frequent histological misinterpretation, in particular, as a peculiar granulomatous reaction. In our case, the primary tumour presented a variant morphological pattern so closely mimicking a cavernous angiosarcoma as to mislead several reputable opinions. Later recurrences and metastases were typical of ES, while a focal angiomatoid pattern was maintained. The morphology and immunoreactivity to a wide spectrum of tumour markers is compared with that of six file cases of classical ES. Retrospectively, all neoplastic lesions in our patient were ES. In young adults, lesions of the upper extremity, even when angiomatoid or haemorrhagic, should raise a suspicion of ES. Once epithelioid sarcoma is suspected, the differential diagnosis can be elucidated on immunohistochemical grounds. Early diagnosis provides the best opportunity for radical surgery at a stage when the tumour has not spread locally or disseminated systemically.