Pleomorphic Adenoma of the Salivary Gland in Two Prairie Dogs (Cynomys ludovicianus)

Abstract

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. (J Toxicol Pathol 2003; 16: 171-173)

Spontaneous Poorly Differentiated Carcinoma with Cells Positive for Vimentin in a Salivary Gland of a Young Rat

“…Spontaneous epithelial tumors of salivary glands in rats are rare (Neuenschwander and Elewell 1990; Elwell et al 1990). So far, several cases in rodents have been reported: epithelial neoplasm in a Wistar rat (Sasaki 1982); adenocarcinoma in a rnu/rnu nude rat (Halter, Wetherall, and Holscher 1983); pleomorphic adenomas in a Sprague-Dawley rat (Okada et al 1985), a B6C3F 1 mouse (Hagiwara et al 1993), and prairie dogs (Ozaki and Narama 2003); poorly differentiated carcinoma in a Sprague-Dawley rat (Tsunenari et al 1997); and papillary cystadenocarcinoma in a Fischer 344 rat (Hosokawa et al 2000). In these reports, the tumor cells had obvious epithelial features (epithelial structures, ductal structures, cysts with luminal papillae, squamous cell differentiation, or positive reaction for pankeratin).…”

A Spontaneous Epithelial-Myoepithelial Carcinoma of the Submandibular Gland in a Sprague-Dawley Rat

“…However, only a few cases of epithelial-myoepithelial carcinoma (EMC), which is morphologically characterized by the proliferation of tumor cells consisting of epithelial and myoepithelial components, have been reported in humans 11 , 12 , 13 . In comparison with humans, the histogenetic classification of salivary gland tumors in rodents is very simple 14 . To date, the term EMC has not been used for the classification of a rodent salivary gland tumor.…”

“…In the salivary gland, criteria that have been reported to be helpful in differentiating between benign and malignant tumors include cytological atypia, mitotic activity and tumor infiltration into the surrounding salivary gland or other normal tissues 14 . In this case, rapid tumor growth, a fish-flesh sarcomatoid gross appearance, a diffuse solid growth pattern, the lack of any clear acinar structure or little tubular structure, prominent mitotic figures, necrotic foci and a tumor infiltrative margin, features associated with malignant behavior, were microscopically observed.…”

Pleomorphic adenoma of the labial gland, characterized by reticular pattern of myoepithelial cells in a dog

“…The proliferation patterns of myoepithelial cells are myxoid, solid, reticular/anastomosing, pseudocystic and pseudoglandular [ 1 , 10 ]. In rodents, spontaneous pleomorphic adenomas of the salivary gland are reported in prairie dogs ( Cynomys ludovicianus ) [ 9 ]. The tumors in prairie dogs consist of ductal or trabecular proliferation of luminal epithelium admixed with solid or diffuse proliferation of myoepithelium.…”