EPITHELIOID BENIGN FIBROUS HISTIOCYTOMA OF SKIN - CLINICOPATHOLOGICAL ANALYSIS OF 20 CASES OF A POORLY KNOWN VARIANT

Twenty new cases of epithelioid fibrous histiocytoma, a distinctive but poorly recognized variant of cutaneous benign fibrous histiocytoma are described. Twelve patients were male and eight were female. The age of the patients ranged from 7 to 80 years (median 40 years). Six lesions arose on the lower limb, five on the upper limb, three around the shoulder, two on the abdomen and one each on the eyelid, inner canthus and anal margin. In one case the age and site were not stated. All lesions presented as a solitary, polypoid or slightly raised cutaneous nodule, ranging in size from 0.5 cm to 2 cm in greatest diameter. Follow-up in 14 cases (mean 22.7 months) revealed local recurrence after 42 months in one case. Histologically, the more polypoid tumours were characterized by an epidermal collarette. In all lesions prominent polygonal or rounded epithelioid cells with abundant eosinophilic cytoplasm, a vesicular nucleus and small eosinophilic nucleoli accounted for at least 50% of the tumour cell population. Individual cells were separated by somewhat hyalinized collagen, containing prominent blood vessels and a sparse mononuclear inflammatory cell infiltrate. The edge of the lesions, especially those that were non-polypoid, often showed more typical features of ordinary fibrous histiocytoma. The main differential diagnosis is with other cutaneous epithelioid neoplasms, especially Spitz naevus.