Evaluation of tumour associated macrophages in different histopathological types and grades of canine mammary tumours

Canine mammary tumours (CMTs) are the second highest reported tumours in female dogs, following skin tumours. Human breast cancers (HBCs) and CMTs share common clinical and molecular features and hence, CMTs are considered as ideal models to study the different aspects of HBC. The study utilised samples from 25 CMT suspected cases presented to University Veterinary Hospitals in Thrissur district from December 2020 to October 2021. The tumour samples were analysed histopathologically and the lesions were classified. Among the 25 cases, one was identified as ductal hyperplasia, one as a benign myxoma and all the others were found to be malignant neoplasms. Malignant tumours were further categorised into different histotypes.Histological Malignancy Grading (HMG) was also done in 23 malignant CMTs and 21.74 percent were found to be of grade I, 47.83 per cent were grade II and 30.43 per cent were grade III. Majority of the malignant tumours were simple carcinomas which comprised tubulopapillary, ductal, cribriform, solid and comedocarcinomas. Highly aggressive tumours like cribriform, solid, comedo and inflammatory carcinomas belonged to higher grades, either II or III. Infiltration of tumour associated macrophages (TAMs) was studied in different histotypes and grades of CMTs. It was identified that malignant high grade CMTs had greater TAM infiltration and hence, with further validation TAMs could be effectively used in predicting prognosis and also as a therapeutic target.