Incidence of cytokeratin 20 expressed cells in primitive follicular structure and secondary neoplastic proliferations of nevus sebaceus.

BACKGROUND: Nevus sebaceus of Jadassohn (NSJ) is a complex hamartoma in which various kinds of secondary neoplastic or hyperplastic proliferations such as primitive follicular structure (PFS) may arise. Recently, cytokeratin (CK) 20 expressed cells in PFSs and trichoblastomas of NSJs were demonstrated.

OBJECTIVE: To clarify the nature and relationship among these proliferations, those in other secondary neoplasms and precise CK distributions in such lesional epidermis are examined.

METHODS: 49 cases of NSJ were analyzed clinicopathologically and immunohistochemically using ten monoclonal antibodies against involucrin and CKs.

RESULTS: 15 of 49 cases possessed PFSs, and six cases, of which five were associated with PFSs, possessed seven lesions of secondary neoplasms: four BCC, two syringocystadenoma papilliferum (SAP) and one trichilemmoma. The age distribution of 15 patients with PFSs was significantly higher than that of the other 34 patients without the PFSs. The six patients with secondary neoplasms were statistically situated in a higher age range than the ten cases with the PFSs alone. Although the CK expression in lesional epidermis of NSJs were similar to that of normal epidermis, CK20 expressed cells were scattered in the PFSs of 11 cases among the 15 NSJs, but not in the other four cases. Three of the four cases were associated with BCC in which CK20 was not expressed.

CONCLUSIONS: From the statistical analysis, we presumed that the existence of the PFSs indicates potency to develop secondary neoplasms. Moreover, the absence of CK20 expressed cells (Merkel cells) in the structures was speculated to predict the development of BCC in the future.