Histopathology attributes of Fox–Fordyce disease

Background  Fox–Fordyce disease is a rare chronic papular condition with a very characteristic clinical presentation but a nonspecific histopathology. Its traditionally described histopathologic features have been criticized as variable and indistinct. Recently, a perifollicular infiltrate of histiocytes with foamy cytoplasm has been described as a consistent and reliable diagnostic finding. Methods  To evaluate the traditional and most recently described histopathologic and immunohistochemical attributes of Fox–Fordyce disease, we performed a computerized search of specimens in two dermatopathologic databases in Puerto Rico from the years 2000–2010. An additional specimen was donated by a dermatopathologist from an outside institution. Three cases were evaluated using hematoxylin–eosin-stained sections. The tip of an axillary lipoma excision specimen was used as the control tissue. Periodic acid-Schiff, colloidal iron, and immunoperoxidase staining for CD68 and c-kit (CD117) were performed in all specimens. Results  We were able to verify traditionally described histological features such as infundibulum dilation, hyperkeratosis, plugging, acanthosis, and lymphohistiocytic infiltrate. Infundibular spongiosis was also common. A perifollicular foam cell infiltrate was the most distinct pathologic feature among our cases. The periodic acid-Schiff staining patterns suggested that the foam cell cytoplasm material might be similar in nature to the apocrine gland secretion content. Conclusions  Our results confirmed that a perifollicular foam cell infiltrate is the most distinct histopathologic feature. In addition, findings suggest that the intracytoplasmic foam cell material may be similar in nature to the apocrine gland secretion.