Hybrid Cyst Coexisting with Glomus Coccygeum

ABSTRACT

A 36-year-old female patient with a mass in the coccygeal region underwent surgical removal of the mass, and this revealed a hybrid cyst in coexistence with a glomus coccygeum. This unusual cutaneous cyst had an epithelial lining composed of keratinizing, stratified squamous epithelium with an intact granular layer immediately adjacent to apocrine cells, and the apocrine cells showed the characteristic features of "decapitation secretion". The glomus coccygeum, which is a minor finding in specimens from the sacral area and it may represent a diagnostic challenge to the unaware observer, was incidentally identified in the dermis. The glomus coccygeum was located beneath the epithelial transition area of the hybrid cyst. Immunohistochemical analysis revealed that the cytoplasm of the epithelioid glomus cells was positive for smooth muscle actin, and these epithelioid glomus cells were arranged in concentric layers around blood vessels, and the cellular stroma surrounding the glomus bodies were positive for S-100 protein.