Immunohistochemical characterization of normal canine Merkel cells

Cutaneous Merkel cells (MCs) have been well documented in humans, but less in other mammals. In dogs, there are only a few references about immunohistochemical characterization of MCs. We present the immunohistochemical profile of MCs in the dog for the most reliable antibodies used in human medicine. Tissue samples from several locations were obtained from five adult dogs of both sexes and different age and breed, fixed in 10% buffered formalin, embedded in paraffin wax and cut in 3-mum tissue sections. The ABC method was used with different poly- and monoclonal antibodies. Positive immunoreaction was found in MCs of hair follicles, skin and mucosae of several locations in each dog studied for anticytokeratins 8, 18 and 20, anti-neurofilaments, anti-chromogranin A, anti-neuron-specific enolase, and anti-synaptophysin. Immunoreaction was always cytoplasmic with differences in intensity, pattern of intracytoplasmic distribution and reaction type. Other cytokeratins, anti-S100 protein, anti-vimentin and anti-glial fibrillary acid protein were absent in canine normal MCs.