34. Recurrent vulvar plexiform schwannoma: an unusual variant in an unusual site

Abstract

A 5-year-old girl presented with a 3 year history of a slow-growing lump in the right labia minora. On examination, a 20×15 mm mass was attached to the overlying vulva skin. After an initial incomplete resection the lump recurred twice, with subsequent repeat excisions 10 and 12 years after initial presentation. Microscopic examination of all three excisional biopsies revealed classical histological features of plexiform schwannoma, namely Antoni A and B areas including Verocay bodies and a multinodu-lar architecture. The most recent excision performed in 2012 also contained scattered bizarre pleomorphic nuclei, consistent with ancient change. Diffuse strong positive staining for S100 was seen. Plexiform (multinodular) schwannoma is an uncommon variant of schwannoma, accounting for approximately 5%. This variant is characterised by a multinodular growth pattern, and can occur in both conventional and cellular types of schwannoma. Plexiform schwannomas can occur in both superficial and deep soft tissues, however the vulva is an uncommon site. Most cases of plexiform schwannoma have no association with neurofibromatosis. Plexiform neurofibroma is an important differential diagnosis to exclude. As seen in our case, plexiform schwan-noma can recur locally, which is thought to be related to the mul-tinodular growth pattern. Malignant transformation and distant metastases of plexiform schwannoma have not been reported.