Cutaneous Cellular Pseudoglandular Schwannoma: An Unusual Histopathologic Variant.

Cellular schwannoma and pseudoglandular schwannoma are both previously described rare variants of schwannoma. The authors present an unusual case of a cellular spindle cell neoplasm with prominent gland-like structures, having features of both variants. The nature of this lesion was confirmed by histology and immunohistochemistry, with diffuse and strong S100 and membranous collagen type IV staining. The gland-like structures were lined by S100 + cells and contained proteinaceous, mucicarmine-negative material, supporting a degenerative, not true glandular, phenomenon. This is the first case of a cutaneous schwannoma demonstrating both marked cellularity and pseudoglandular formation, which the authors have designated cutaneous cellular pseudoglandular schwannoma. Recognition of this extremely rare variant will help avoid diagnostic confusion and overtreatment of this benign entity.