EPITHELIOID GLOMUS TUMOR

Reported are five cases of an unusual histological variant of glomus t umor that we have designated epithelioid glomus tumor, Unlike conventi onal glomus tumors, which consist of small polygonal cells with dark r ound nuclei and scanty cytoplasm, the epithelioid lesions were compose d of large polygonal to spindle-shaped cells with abundant eosinophili c cytoplasm and large, irregularly shaped nuclei: The cells had both e pithelioid and myoid qualities, Two of the cases studied were predomin antly epithelioid, with small remnants of conventional glomus tumor at the periphery. The three other lesions were purely epithelioid, Epith elioid glomus tumors are of particular importance because they may be mistaken for other lesions histologically, Both benign and malignant e pithelial lesions may be considered in the differential diagnosis; spi ndle-cell lesions, such as schwannoma, leiomyoma, hemangiopericytoma, and others, are in the histological differential diagnosis, Immunohist ochemical and ultrastructural studies indicated that epithelioid glomu s tumors had characteristics identical to those of conventional glomus tumors: the cells showed features consistent with smooth muscle deriv ation, The epithelioid areas frequently exhibited cytological atypical ity-features that we believe to be a manifestation of cellular degener ation or senescence (analogous to ''ancient'' change in schwannomas or symplastic change in leiomyomas) rather than evidence of neoplastic p rogression, Simple surgical excision seems to have been curative (mean duration of follow-up of 4 years in the three cases in which such inf ormation was available). To our knowledge, no similar cases have previ ously been reported. Copyright (C) 1995 by W.B. Saunders Company