Spontaneous Granular Cell Tumor of Cecum in a Laboratory Beagle

A spontaneous granular cell tumor was found in the cecum of a 9-month-old female beagle. The tumor cells were distributed widely and multifocally throughout the cecal submucosa and basal portion of the lamina propria, but never formed macroscopic nodular lesions. Partial infiltration into the muscular layer was observed, but neither metastasis nor invasion to other tissues was detected. The tumor cells were oval to polygonal and were characterized by abundant eosinophilic and PAS positive granules in the cytoplasm. Immunohistochemically, the tumor cells were positive for vimentin, but negative for S-100 protein, NSE, desmin, lysozyme, and α1-antichymotripsin. Ultrastructurally, various numbers of lysosomal bodies containing lamellar and membranous structures were present in the cytoplasm. Neither basal lamina nor cell-to-cell communications were observed. This is the first report of canine granular cell tumor arising in the cecum and is of interest as it occurred in a young laboratory beagle.