Abstract
Skin tumors on the lumbosacral area and the head in a German shepherd dog and a domestic cat, respectively, were removed surgically. Histopathologically, both tumors consist of extremely enlarged cysts resembling hair follicles. Multiplication of basophilic tumor cells and ghost cells were observed in the follicular wall and the lumens, respectively. Thus, the tumors were diagnosed as trichoepithelioma. We then computed the incidence rates of trichoepithelioma in histopathological specimens of tumors in dogs and cats submitted to a single diagnostic laboratory. The incidence rate of the tumor in the dog was 3.26%, whereas it was only 0.36% in the cat. To the authors' knowledge, this is the first report on trichoepithelioma in cats in Japan. It is also suggested that the low incidence rate of trichoepithelioma is associated with infrequent reporting of the tumor in feline cases.
