Cutaneous pseudosarcomatous polyp: a recently described lesion.

Three cases of cutaneous pseudosarcomatous polyp, a lesion recently described in the dermatopathology literature, are reported here. These benign proliferations display dramatic cytologic pleomorphism, but despite their disquieting morphological features, they have behaved in a benign fashion to date. All 3 lesions in this study were clinically innocuous, with 1 having been present for 1 year and another for 2 years. The first lesion arose on the back of a 30-year-old man, the second on the nasal columella of a 65-year-old woman, and the third on the back of a 91-year-old woman. All 3 had the typical architecture of a fibroepithelial polyp (acrochordon) with widely separated stellate cells occupying a myxoid to collagenous stroma. Markedly pleomorphic stellate cells were widely dispersed, with an increased density of atypical cells beneath the epidermis and in small foci of adipose tissue in 1 case. Multinucleated cells, some with a floret-type configuration, were also observed. One of the polyps demonstrated focal mild hyalinization of vessel walls. Only rare mitotic figures were identified in 2 cases, but 1 showed atypical forms. Immunohistochemically, the atypical cells reacted diffusely for vimentin and variably for CD34 and factor XIIIa, but they lacked smooth muscle actin and desmin. Cutaneous pseudosarcomatous polyps can be added to the list of pathologic entities with symplastic or pseudomalignant features.