Hyalinizing spindle and epithelioid cell nevus. A study of five cases of a distinctive histologic variant of Spitz's...

Five cases are described of a distinctive histologic variant of benign spindle and epithelioid cell nevus characterized by extensive and prominent stromal hyalinization. The lesions consisted of a proliferation of spindle or epithelioid nevocytes scattered singly or in small clusters in the dermis and surrounded by abundant paucicellular hyalinized or collagenous stroma. Three patients were men and two were women. Their age range was 23 to 45 years (mean, 32). Two of the lesions were located in the head and neck region, two in the lower extremities, and one in the trunk. Immunohistochemical strains showed positive staining of the spindle or epithelioid cells with S-100 protein and vimentin; stains for keratin, EMA, CEA, actin, and desmin were all negative. Van Gieson and trichrome histochemical reaction demonstrated the collagenous nature of the hyalinized intercellular matrix; Congo red, crystal violet, and alcian blue stains were all negative. The etiology and pathogenesis of the intercellular hyalin deposits are unknown, but they probably represent a regressive phenomenon in longstanding or involuting lesions. Hyalinizing Spitz nevus must be included in the differential diagnosis of cutaneous lesions exhibiting a prominent hyalinized stroma and must be differentiated from other dermal neoplasms, particularly cutaneous metastases from occult internal malignancies and malignant melanoma.