Nodular fasciitis of the vulva. Report of a case with immunohistochemical study.

Nodular fasciitis (NF) is a tumor-like condition composed of fibroblasts and myofibroblasts, usually located in the subcutaneous tissue of the extremities. Histologically, it can mimic a myogenic sarcoma because of its hypercellularity, brisk mitotic rate and the presence of actin. NF of the vulva is rare with only eleven cases reported in the English literature. A 40 year-old woman developed a nodule in labium majus that was surgically excised. Microscopical examination revealed a typical example of NF with occasional multinucleated giant cells. The immunohistochemical study showed positivity for vimentin and muscle-specific actin in the spindle cells. The multinucleated cells stained with CD68. MIB-1 was positive in less than 5% of the cells which indicated a low proliferative activity. The patient has been followed for 5 years and no relapses occurred. The rarity of this lesion in the vulva and the potential difficulties for its diagnosis led us to report the clinical and immunohistochemical study of this case.