Oncocytic metaplasia of canine palatine ductal epithelium

Oncocytic metaplasia of palatine gland ducts was demonstrated by light and electron microscopy in seven out of 54 dogs. Oncocytes were recognized as distinct swollen epithelial cells with bright eosinophilic cytoplasm, small dark nuclei and scattered microvilli at the luminal surface. Their cytoplasm contained numerous tightly packed mitochondria, which varied in size and shape. Some oncocytes formed nodular hyperplastic foci that were easily recognized by low-power light microscopy. Oncocytic metaplasia appears to be a common incidental finding in palatine ductal epithelium of older dogs.