Invasive Ductal Mammary Carcinoma in a Cow

Abstract

Background: Mammary gland carcinoma is a malignant epithelial neoplasm that can be classified as solid, papillary, ductal, invasive micropapillary, or invasive ductal. They are rarely diagnosed in livestock animals. Reports describing the breast as primary site of tumor in cows are scarce. In this case report, pathological and clinical findings of primary carcinoma of
the mammary gland in a cow are reported.
Case: A 7-year-old crossbred pregnant cow exhibited an increase in volume in the posterior region of the udder. Palpation raised suspicion of mastitis. The prefemoral lymph nodes (LNs) were enlarged. After calving, the clinical condition worsened, and edema was observed in the ventral region, from the udder to the neck. Poisoning by Amaranthus sp. was suspected. The cow died fifteen days after calving. Necropsy was performed. The affected mammary gland and its LNs, fragments of abdominal organs, brain, pelvic limbs, and udder skin were routinely prepared and stained with hematoxylin and eosin. Gross examination revealed significant alterations in the mammary gland, and in the mammary and prefemoral LNs. The mammary gland was firm and swollen; with loss of normal architecture, and released purulent, pinkish, fetid contents. The mammary LNs were enlarged, with diffuse coalescent
multifocal lesions, loss of corticomedullary delimitation, and the content was similar to that observed in the udder. The internal prefemoral LNs were also enlarged and contained the same fetid contents. Histopathology revealed proliferation of neoplastic ducts coated by numerous neoplastic cells; some areas were solid. There was moderate to severe pleomorphism, with moderate anisocytosis and anisokariosis. Most of the cells had vesicular nuclei, with up to two evident nucleoli. Other cells had dense chromatin, and moderately eosinophilic cytoplasm. There was marked cell dissociation, and cell detachment. The central portions
of the ducts were necrotic, with a predominantly neutrophilic inflammation. The mitotic index was low, but some areas had up to four mitotic figures per high power field. Numerous areas exhibited multiple foci of deposition of organized granular basophilic material, interpreted as mineralized areas, and stained positively for Von Kossa stain. Some areas of the mammary gland exhibited proliferative acini and ducts, composed of a single layer of cuboidal or columnar cells with moderately eosinophilic, vacuolated cytoplasm, and a basal rounded nucleus of generally aggregated chromatin (mammary hyperplasia). Many acini were dilated, and some contained circumscribed basophilic material (corpora amylacea). The structural architecture of the LNs was altered by malignant neoplastic infiltration, similar to that found in the mammary gland. No metastatic lesions were detected in the other organs. Immunohistochemistry (IHC) was performed using the streptavidin-biotin-peroxidase technique. Anti-pan-cytokeratin and antivimentin antibodies were used. Neoplastic cells exhibited strong and uniform cytoplasmic immunoreactivity for pan-cytokeratin. Expression of vimentin was absent in the neoplastic cells, but was present in the connective tissue associated with the neoplasm.
Discussion: Invasive ductal mammary carcinoma was confirmed by histopathological and IHC analyses. Edema can be explained by the neoplasm in the mammary gland and in the mammary LNs, with accumulation of fluid in the interstitium, caused by growth of the tumor and compression of large blood and lymphatic vessels. IHC confirmed the epithelial origin of the tumor and demonstrated the presence of epithelial tumor cells in the LNs, proving to be metastatic. Similar findings
were reported in a cow with a highly aggressive secretory mammary carcinoma, in which neoplastic cells exhibited immunoreactivity to cytokeratin, indicative of their epithelial origin.
Keywords: histology, immunohistochemistry, neoplasms, ruminant.