Clinicopathological features and expression of four keratins (K10, K14, K17 and K19) in six cases of eruptive vellus hair cysts.

Six cases of eruptive vellus hair cysts (EVHC) were evaluated for histopathology and the immunohistochemical profile of Ki-67 and four keratins (K10, K14, K17 and K19). The pathological hallmark of EVHC was the existence of vellus hair shafts within the cystic cavity, but atypical pathological changes included two or three cysts and a foreign-body granuloma in three cases. Our results demonstrate that atypical pathological changes are not uncommon in EVHC, and indicate that based on keratin expression, it is likely that EVHC is derived from the infrainfundibulum and sebaceous duct.