Abstract
Two masses adjacent to the salivary glands of two Prairie dogs which were surgically removed and examined histopathologically as well as immunohistochemically, were diagnosed as pleomorphic adenomas. Histologically, each mass had a thin fibrous capsule, compressed surrounding tissue, and was lobulated by delicate connective tissue. The lobules mainly consisted of a solid growth of small ovoid-to spindle-shaped cells, and contained small duct or tubule lined with monolayered cuboidal epithelial cells. The amount of connective tissue stroma varied in different parts of the tumor mass, accompanied occasionally by a myxomatous stroma-rich area. Tumor cells in the solid growth area had indistinct cell borders, and usually showed spindle-like features resembling myoepithelial cells. Mitosis was prominent, whereas cellular pleomorphism was not seen. Tumor cells forming the tubular structure were positive for cytokeratin 19 and negative for smooth muscle actin (SMA), while the ovoid- to spindle-shaped tumor cells of the solid growth area were positive for SMA and negative for cytokeratin 19. Our results indicated that immunostaining was a useful and powerful method for the diagnosis of cell differentiation of salivary gland tumor cells.
