Morphologic and immunohistochemical features of Merkel cells in the dog

Merkel cells (MCs) are specialized skin receptors characterized by their particular location and close association with nerve terminals. They also are cells with a presumptive neuroendocrine function and are considered as part of the diffuse neuroendocrine system. By using commercially available monoclonal and polyclonal antibodies in samples of dog skin, MCs were properly distinguished from other clear cell types in the epidermis. They expressed cytokeratins 7, 8, 20, EpCAM, NSE, CGA, SYN, S100 protein, and NF, presented diverse cytological features and arrangements depending on the location considered, and showed pronounced heterogeneity with markedly different expression and distribution patterns for antibodies used. Anti-CK20 presented as the most reliable and specific antibody for their identification. The present study increases our knowledge of MCs and establishes a basis for future studies of the role(s) of the MCs in diseased tissues of the dog skin, including the cutaneous neuroendocrine (Merkel cell) tumour.