Solitary cutaneous myofibromas in adults: report of six cases and discussion of differential diagnosis.

Six solitary, dermal or subcutaneous lesions occurring in adult patients are presented. These masses had a circumscribed, lobulated configuration; they were composed of fusiform and epithelioid cells that lacked atypical nuclear features. The pattern of growth featured fascicles and nests, a myxofibrous stroma, and prominent blood vessels with a focally "hemangiopericytoid" appearance. Immunohistochemical analyses showed uniform reactivity for vimentin and alpha isoform-actin, with negativity for desmin and neural determinants. The overall appearance of the lesions was similar to that of "infantile myofibromatosis," and corresponded to previous descriptions of "solitary myofibroma(tosis)" in adults. Immunophenotypic and ultrastructural support exists for a proposed myofibroblastic nature for such proliferations. Differential diagnostic considerations include neurothekeomas, plexiform fibrous histiocytomas, nodular fasciitis, cutaneous inflammatory pseudotumors, dermatomyofibromas, leiomyomas, and other forms of fibromatosis affecting the skin and superficial soft tissues.