Perineal nodular induration: a trauma-induced mass in a female equestrian.

A 55-year-old female equestrian presented with a 3.5 cm painful left perineal mass. Histologic examination of the excised mass showed a poorly circumscribed mesenchymal proliferation involving fibroadipose and fibrous tissue. The lesion consisted of a bland spindle cell proliferation with areas of fat necrosis, hemosiderin-laden macrophages, multinucleated histiocytes, and extracellular hyalinization with degenerative features. Immunohistochemical studies showed vimentin positivity and no staining for actin, desmin, and CD34. On the basis of clinical, morphologic, and immunostaining findings, the lesion was consistent with a diagnosis of perineal nodular induration. This lesion has been described almost exclusively in avid male cyclists with repetitive perineal trauma. A similar etiology of longstanding and repetitive perineal trauma from horseback riding is postulated for this case. Perineal nodular induration should be considered in the differential diagnosis of perineal masses in women with persistent perineal trauma, such as equestrianism, as well as other similar sport activities.