Merkel Cell Differentiation in Trichoblastoma

The study reported on four cases of trichoblastoma rich in Merkel cells (MCs), involving two men and two women aged 58 to 76 years. MCs were identified using antibodies to keratin 20, chromogranin A, and neuron-specific enolase. The research aimed to better understand the role of MCs in trichoblastoma by examining their distribution in normal adult and fetal skin, as well as in ten cases of sebaceous naevus of Jadassohn (NSJ). MCs constituted 2–20% of the tumor cells in trichoblastomas and were found in normal fetal skin but were rare in normal adult skin. Most NSJ cases showed numerous positive cells with all three antibodies, while associated basal cell carcinomas and syringocystadenoma papilliferum were negative. The findings suggested that hair follicle cell tumors might mimic skin embryogenesis, as fetal follicles contain numerous MCs, whereas adult skin has few.