Differentiation and Apoptosis in Pilomatrixoma

The study investigated pilomatrixoma, a benign skin tumor, focusing on apoptosis and hair differentiation to understand amorphous debris and cyst formation. Among 16 cases, 11 were in the early regressive stage and 5 in the late regressive stage. Tumor nests comprised basophilic, transitional, and shadow cells, with cyst formation evident in all cases. Immunohistochemical analysis showed β-catenin and Lef-1 in basophilic and transitional cells, with differing distributions. Hair keratins were present in transitional and shadow cells but absent in amorphous debris. The TUNEL method indicated apoptosis in transitional and some shadow cells. The findings suggested simultaneous hair keratin production and apoptosis, with irregular β-catenin and Lef-1 expression leading to amorphous debris and cyst formation, unlike normal hair follicles.