Benign glandular schwannoma.

The vast majority of reported glandular schwannomas, the rarest type of divergent differentiation in nerve sheath neoplasms, have been malignant tumors. We describe a benign glandular schwannoma, less than 1 cm in diameter, that developed in the deep subcutaneous region of the left flank of a 36-year-old woman. The glandular component occurred as a single large cyst with an undulating lining occupying the central one third of the lesion and was lined in large part by a well-oriented, flattened, single cell layer of cuboidal to low columnar cells with a basement membrane. This extremely unusual lesion, apparently the fourth benign instance reported, is important for several reasons: (1) it does not appear to be a result of inclusion of previously postulated dermal adnexal glands; (2) it further establishes the existence of a true benign counterpart of the glandular schwannoma, of which pathologists should be aware; (3) it can be distinguished from the recently reported pseudoglandular schwannoma; and (4) it lends additional support to the concept of a direct metaplastic origin of the epithelial element from the schwannian component because of the focal presence of a maloriented pseudoglandular element.