Sclerosing epithelioid fibrosarcoma R.REID, A.BARRETT* & D.L.HAMBLEN* ² University Departments of Pathology, *Radiation Oncology and ² Orthopaedic Surgery, Western Infirmary, Glasgow, UK REID R., BARRETT A. & HAMBLEN D.L. (1996) Histopathology 28, 451–455 Sclerosing epithelioid fibro-sarcoma A case of sclerosing epithelioid fibrosarcoma arising in the thigh of a 40-year-old man is reported. This recently described sarcoma has a distinctive histological appearance which may cause confusion with a variety of other sarcomas with an epithelioid pattern, and indeed with benign soft tissue tumours showing hyalinization. Despite its bland cytology, sclerosing epithelioid fibrosarcoma is capable of metastases, often several years after surgical removal. The patient described here developed lung metastases five years after excision and remains alive a further three years later. The differential diagnosis and possible histogenesis are discussed. Keywords: sclerosing epithelioid fibrosarcoma Introduction In 1995, Meis-Kindblom and colleagues 1 described a series of 25 cases, drawn largely from the files of the Armed Forces Institute of Pathology, of a previously unrecognized and histologically distinctive sarcoma whose peculiar sclerosing pattern could simulate a carcinoma. The tumours arose principally in deep soft tissue and affected mainly adult patients with a wide age range from 14 to 87 years. Since each example contained foci of spindle-celled sarcoma similar to conventional fibrosarcoma, the authors suggested that the tumour was a variant of fibrosarcoma, a conclusion supported to some extent by the ultrastruc- tural appearances. However, the wide variety of antigens expressed by the tumour suggests that fibro- sarcoma may be an inappropriate designation. Although the tumours have a bland cytological appear- ance and mitotic figures are usually sparse, six (43%) of the 14 patients with appropriate follow-up infor- mation developed metastases indicating that the tumour, although slow growing, has fully malignant potential. We report a case of sclerosing epithelioid fibrosarcoma occurring in a 40-year-old man, who is alive with pulmonary metastases eight years after diagnosis. The histological and ultrastructural appear- ances are described together with a discussion of the differential diagnosis and possible histogenesis of this rare tumour. Case report A 40-year-old man presented with a two month history of swelling and an 18 month history of discomfort above the left knee. There was no history of local trauma and no other medical history of note. An indurated mass measuring 6 cm in greatest dimension was palpable in the muscles on the medial aspect of the thigh. Plain radiographs showed that the underlying femur was not involved. An MR scan of the lesion suggested that the femoral vessels were closely applied to the mass and this was confirmed by arteriography. No evidence of other lesions was found by CT scan of the chest or by isotope bone scan. At exploration the swelling was found to lie in the belly of semitendinosus and an open biopsy was carried out which was reported as a sarcoma of uncertain histogenesis showing vascular invasion. The tumour was then resected by an excision of the medial compartment of the thigh along with segments of the femoral artery and vein. The tumour involved adductor magnus, adductor longus and semimembranosus. No adjuvant chemotherapy or radiotherapy was given and the patient remained well for over 5 years. Following a chest infection, an X-ray showed a large well-defined pulmonary metastasis in the lower halfof the right lung field, with smaller pleural-based lesions on the right Histopathology 1996, 28 , 451–455 451 1996 Blackwell Science Limited. Address for correspondence:: Dr R.Reid, University Department of Pathology, Western Infirmary, Glasgow G11 6NT, UK.