HER2-positive feline mammary carcinoma

models have been crucial to increase knowledge about oncogenic mechanisms but due to the limitations of rodents and cell culture approaches, they are viewed as artificial models, whereas the spontaneous tumors in pets are empirically considered to be a more powerful and reliable tool. With the publication and full annotation of cat's genome [1], researchers showed that the genome of the cat was subjected to a very small number of genomic rearrangements when compared to the human genome, reinforcing the general accepted idea that feline mammary carcinomas (FMC) may be a good translational model, also based on their epidemiological and histopathological features that closely resemble those found in the more aggressive breast cancer subtypes. Nowadays, the incidence of feline mammary carcinoma (FMC) is increasing, probably because of the humanized lifestyle of the cat, unregulated environmental factors and better prevention/efficient treatment of infectious diseases. Despite this scenario, few studies have evaluated the protein expression in FMC, in order to uncover new prognostic factors and discover possible therapeutic targets. In two recent studies, we identified in a pool of FMC, the six molecular subtypes described in breast cancer patients, using the broadly accepted IHC-based classification established by St. Gallen International Expert Consensus Panel [2,3]. The results demonstrated that cats with Luminal A mammary carcinomas showed less aggressive clinicopathological features, contrasting with the cats that had triple negative mammary carcinomas which were associated with the lowest survival and disease free survival times, as reported for humans. Additional data on disease progression revealed that lungs, pleura and liver are the organs mostly affected by metastases, with a large heterogeneity in protein expression being found in primary FMC and paired metastases, particularly in distant metastases, where both estrogen and progesterone receptors are usually downregulated, in contrast, to cytokeratin 5/6 and Ki-67 expression, leading to an enrichment of triple negative/basal-like lesions over luminal A/B metastases, similar to what is reported in woman. Concerning the role of the feline homologue of human epidermal growth factor receptor-2 (HER2) in mammary Editorial carcinoma, some reports have brought fragmentary data revealing that the molecular mechanisms underlying HER2 tumorigenesis may not be fully conserved between cat and man. The overexpression of this transmembrane glycoprotein that belongs to the epidermal growth factor receptor family, is correlated with a rapid tumor growth and progression in breast patients and because of this, is routinely measured by immunohistochemistry and by in situ hybridization, since in …