Metastatic ovarian papillary cystadenocarcinoma to the small intestine serous surface: report of a case of high-grade histopathologic malignancy

Ovarian cystadenocarcinoma is characterized by marked heterogeneity and may be composed of an admixture of histologic growth patterns, including acinar, papillary and solid. In the present study, a case of isolated small intestine metastasis of ovarian papillary cystadenocarcinoma was reported. A 7-year-old female mixed-breed dog presented with a mass in the left upper quadrant with progressive enlargement of the abdomen, periodic bloody discharge from the vulva and incontinence. The tumor was histologically characterized by the presence of cysts and proliferation of papillae, both lined by single- or multi-layered pleomorphic epithelial cells. Furthermore, the mass was composed by intense cellular and nuclear pleomorphism and numerous mitotic figures. These findings indicate a tumor of high-grade malignancy with infiterative tumor cells resembling the papillary ovarian tumor in the serosal surface of the small intestine along with an intact serosa. Immunohistochemically, tumor was positive for CK7 and negative immunoreactivity for CK20. The histopathologic features coupled with the CK7 immunoreactivity led to a diagnosis of high grade ovarian papillary cystadenocarcinoma. To the best of our knowledge, this is the first case of small intestine serousal surface metastasis from ovarian papillary cystadenocarcinoma.