Benign Mixed Mammary Tumour with Hepatoid Gland Differentiation in a Dog.

A 10-year-old spayed female Shih Tzu underwent surgery to remove a tumour (8 mm diameter) in the right 4th mammary gland. Histopathologically, the tumour consisted of four different components: luminal epithelial cells, myoepithelial cells, cartilage and well-differentiated hepatoid gland-like cells. There were multiple nests composed predominantly of hepatoid gland-like tissue with a small number of tubules formed by luminal epithelial cells at the periphery, in which continuity between the two components was seen. Immunolabelling for cytokeratins (CK14, CK18 and CK19), p63 and α-smooth muscle actin clearly distinguished the neoplastic luminal epithelial, myoepithelial and hepatoid gland-like cells. The immunohistochemical phenotype of the hepatoid gland-like neoplastic cells was identical to that of normal hepatoid gland cells. Based on these findings, a diagnosis of benign mixed tumour of the mammary gland with differentiated hepatoid gland cells was made. To our knowledge, this is the first report of a canine mammary tumour with hepatoid gland differentiation.

The immunohistochemical detection of peroxiredoxin 1 and 2 in canine spontaneous vascular endothelial tumors.

Peroxiredoxin (PRDX) is an antioxidant enzyme family with six isoforms (PRDX1-6). The main function of PRDXs is to decrease cellular oxidative stress by reducing reactive oxygen species, such as hydrogen peroxide, to H2O. Recently, it has been reported that PRDXs are overexpressed in various malignant tumors in humans, and are involved in the development, proliferation, and metastasis of tumors. However, studies on the expression of PRDXs in tumors of animals are limited. Therefore, in the present study, we immunohistochemically investigated the expression of PRDX1 and 2 in spontaneous canine hemangiosarcoma (HSA) and hemangioma (HA), as well as in selected normal tissue and granulation tissue, including newly formed blood vessels. Although there were some exceptions, immunolocalization of PRDX1 and 2 in normal canine tissues was similar to those in humans, rats, or mice. In granulation tissue, angiogenic endothelial cells were strongly positive for PRDX1 and 2, whereas quiescent endothelial cells in mature vessels were negative. Both PRDX1 and 2 were significantly highly expressed in HSA compared to HA. There were no significant differences in the expression of PRDX1 and 2 among the subtypes and primary sites of HSA. These results suggest that PRDX1 and 2 may be involved in the angiogenic phenotypes of endothelial cells in granulation tissue as well as in the behavior in the malignant endothelial tumors.