Spiradenoma and cylindroma originate from the hair follicle bulge and not from the eccrine sweat gland: an immunohistochemical study with CD200 and other stem cell markers

Background Spiradenoma and cylindroma have historically been described as sweat gland tumors and have often been considered to be of eccrine lineage. However, (a) associations with trichoepitheliomas in Brooke-Spiegler syndrome or with trichoepitheliomas and milia in Rasmussen syndrome, (b) neoplastic combinations with hair follicle tumors in solitary cases, and (c) anatomical considerations support a folliculosebaceous-apocrine lineage. Follicular stem cell markers may allow for further characterization of these neoplasms. Methods A total of 97 tumors were examined for the expression pattern of follicular stem cell markers cytokeratin 15 (CK15), cytokeratin 19 (CK19), pleckstrin homology-like domain, family A, member 1 (PHLDA1), and CD200. The tumors were comprised of 27 spiradenomas, 30 cylindromas, 16 hidradenomas, 19 poromas, 4 dermal duct tumors and 1 hidroacanthoma simplex. Results All spiradenomas and cylindromas were CD200-positive whereas the other tumors classified as eccrine in lineage were all CD200-negative. CK15 also discriminated between spiradenomas and cylindromas and the remaining neoplasms but not to the degree of CD200. PHLDA1 and CK19 were noncontributory. Conclusions It is concluded that both spiradenoma and cylindroma are not eccrine but follicular tumors. More specifically, it is proposed that both adnexal neoplasms are derived from the hair follicle bulge and as such represent one of the least differentiated follicular tumors.