Enterobious vermicularis (pinworm) infestation of the vulva: report of 2 cases of a pseudoneoplastic lesion mimicking squamous carcinoma.

Enterobious Vermicularis (pinworm) infestation outside the gastrointestinal tract is rare. We report 2 patients with vulval involvement, one of whom presented with a clinically suspicious, rapidly growing mass. The histology of both lesions showed similar features of epidermal proliferation in the form of hyperkeratosis, acanthosis, and papillomatosis; this pseudoepitheliomatous hyperplasia raised the possibility of a well-differentiated squamous carcinoma. There was associated inflammation in both cases, including large numbers of eosinophils in 1 case. On the surface or within the keratin layer, structures with the morphology of enterobious vermicularis eggs were identified. In reporting this unusual pseudoneoplastic phenomenon, we stress the necessity for the pathologist to consider and look for parasites in proliferative squamous lesions of the vulva, especially when there is an associated inflammatory infiltrate rich in eosinophils.