The Study of the Clinical, Histopathological Features of Pilomatricoma and the Differentiation to Normal Hair Follicles / 대한피부과학회지

ABSTRACT

BACKGROUND: Pilomatricoma is a benign appendageal tumor characterized by basaloid and shadow cells. Differentiation towards normal hair follicles is often observed in this condition. OBJECTIVE: The purpose of this study was to analyze the clinical and histopathological features of pilomatricoma and to confirm diverse types of differentiation towards normal hair follicles, and its origin. METHODS: We retrospectively reviewed medical records and histopathological findings of 64 patients who had visited our hospital in the last 7 years. The evolutional stages of tumor and differentiation were analyzed through histopathological findings. RESULTS: The majority of the tumors occurred in the first two decades (69.8%). Unlike previous reports, the male to female ratio was 1.11. The mean duration was 11.8 months. The predilection sites were the upper extremities (40.8%), face (33.8%), neck (15.5%), back (2.8%), scalp (2.8%), and thigh (2.8%) in that order. Histopathologically, most of the tumors were located in the lower dermis (76%) and enclosed by pseudocapsules. The evolution of tumor was divided into four groups- early, fully developed, early regressive, and late regressive stage, as previously reported. Our 71 cases were classified as 2 early, 16 fully developed, 34 early regressive, and 19 late regressive stage. Calcification (60.5%) and ossification (8.4%) were observed, and the ratio increased as the tumor aged. Inflammatory cell infiltration and multinucleated giant cells were observed disorderly. Differentiation to normal hair follicles was observed 14 cases to infundibulum, 10 isthmus, 17 outer root sheath, and 11 inner root sheath. CONCLUSION: Pilomatricoma is a benign tumor that differentiates toward the hair cortex. Basaloid and shadow cells correspond to hair matrix cells and immature hair cortex cells, respectively. Basaloid cell can also differentiate to normal hair follicles.