[Sclerotic fibroma].

The clinical and histological diagnosis of sclerotic fibroma is important because of its potential association with Cowden's syndrome. Despite its distinctive histological appearance the lesion is often mis-diagnosed. We therefore present five of our own cases (2F, 3M) in which the tumor was located on the head (n = 2), arm (n = 2) and leg (n = 1), respectively. Clinically, the lesions were white to flesh-colored firm nodules ranging in size from 0.5 to 1.2 cm. None of our patients revealed any clinical evidence of Cowden's disease. Simple surgical excision seems to be curative. Histologically, they were well-circumscribed but not encapsulated dermal nodules composed of stori-form-arranged sclerosing collagen bundles and vimentin-positive fibroblastlike cells interspersed in three cases by a number of alpha-smooth-muscle actin-positive myofibroblasts. Approximately 50% of cells (dermal dendritic cells (DD)) also reacted for factor XIIIa evenly scattered throughout the lesion in contrast to the very few (< 5%) CD34+ DD found predominantly at the lower border, thus possibly reflecting the distribution of these cells in normal skin. Sclerotic fibroma expands the spectrum of fibrous lesions that may express alpha-smooth-muscle actin.