Biphasic Feline Mammary Carcinomas Including Carcinoma and Malignant Myoepithelioma

Abstract

Feline mammary tumors are usually malignant and aggressive carcinomas. Most cases are simple monophasic carcinomas (1 epithelial population), and additional phenotyping is usually not needed. In this study, we describe 10 malignant mammary tumors from 9 female cats that had unusual histomorphology: they appeared biphasic, with 2 distinct cell populations. Initially, they were morphologically diagnosed as either carcinosarcoma (1/10) or malignant pleomorphic tumor (9/10) of the mammary gland, as the latter did not match any previously described histological subtype. Immunohistochemistry (IHC) was performed for pancytokeratin, cytokeratins 8 and 18, cytokeratin 14, cytokeratins 5 and 6, vimentin, p63, calponin, alpha-smooth muscle actin, Ki-67, ERBB2, estrogen receptor alpha, and progesterone receptor. In 7 of 10 cases, the biphasic nature was confirmed and, on the basis of the IHC results, they were classified as carcinoma and malignant myoepithelioma (4/10), ductal carcinoma (1/10), and carcinosarcoma (2/10). The other 3 of 10 cases were monophasic based on IHC. In the cases of carcinoma and malignant myoepithelioma, the malignant myoepithelial cells were 100% positive for vimentin (4/4) and variably positive for p63, calponin, and cytokeratins (4/4). These findings show that, although rare, biphasic mammary carcinomas do occur in cats. In dogs and humans, tumors composed of malignant epithelial and myoepithelial cells have a less aggressive behavior than certain simple carcinomas, and therefore, their identification might also be clinically significant in the cat.

Histological Characterization of Some Feline Mammary Gland Tumors with Whole Slide Images Scan as a Trial of Remote Diagnosis

“…Unlike the results ofMorris (2013); Mills et al (2015) andCassali et al (2018) that reported lobular hyperplasia and duct ectasia as a single lesions. Many of our cases showed those changes along with different patterns of malignant carcinomas.In agreement with Mills et al(2015);Sammarco et al (2020) andChen et al (2020), FMT were usually associated with intense stromal fibrosis (scirrhous reaction) while,…”

“…As previously described by Sammarco et al (2020), presence of biphasic FMT not a quite common finding that could not be distinguished easily by histologic examination, in our results a case of proliferating pleomorphic population of vimentin positive myoepithelial cells was reported. Glycogen-rich carcinoma with its described histologic patterns was similar to that reported in a Persian queen by Campos et al (2016).…”

“…Masons trichrome stain (MTC) and some tissue immune markers were used. Histological criteria were carefully described for each sample including, the carcinoma type, degree of necrosis, stromal scirrhous reaction, peripheral lymphocytic infiltration, desmoplasia and local invasion, vascular invasion and clearance of the surgical margins (Sammarco et al, 2020).…”

“…Tissue sections were incubated with primary antibodies (CK8/18 (NCL-L-5D3, 1 in 30 dilution, Novocastra, Newcastle Upon Tyne, UK) and vimentin (V9, 1 in 150 dilution, Dakocytomation) overnight at 4 o C. After washing with PBS, HRP labelled secondary antibody was applied for 2 hours at room temperature, followed by a detection step using DAB substrate kit (Thermo Fisher Scientific, USA). Mayer's hematoxylin was used as counterstain (Sammarco et al, 2020).…”

Mammary Fibroadenoma in Cats: A Matter of Classification

“…The availability of anti-human PR antibodies cross-reacting in animal tissues is, at the moment, an unsolved issue. Previously cross-reacting antibodies are no longer commercially available and those tested did not give robust results after several attempted protocols [16,41,42,[44][45][46].…”