Histomorphological stratification of stromal types associated with canine mammary tumours

Cancer associated stroma (CAS) consists mainly of a cellular fraction comprising fibroblasts, myofibroblasts, inflammatory cells, immune cells, endothelial cells, adipocytes and extracellular matrix (ECM). Recent reports have shown that the cancer stroma including the cellular fraction and ECM undergo considerable reprogramming during the process of tumourigenesis. Though there are some studies on CAS of human breast cancers (HBCs), similar studies are very much limited in canine mammary tumours. Hence, the present study was undertaken to classify the stromal types associated with malignant canine mammary tumours(CMTs). The excisional biopsy samples from 50 numbers of CMTs presented to Kerala Veterinary and Animal Sciences University hospitals at Mannuthy and Kokkalai during the period from November 2019 to December 2021 formed the study material. Histopathological stratification of cancer stroma was done using qualitative evaluation based on the stromal characteristics suggested for HBCs. Accordingly the cancer associated stroma in different tumour samples were classified as fibrotic stroma, inflammatory stroma and mixed stroma. Fibrotic stroma was further classified as mature/ sclerotic, intermediate and immature/desmoplastic types. The grade of tumours in relation to the type of stroma was also analysed and it was identified that with the exception of sclerotic stroma, all other stromal types could be observed in higher grades of CMTs. Desmoplastic and inflammatory stroma were predominantly seen associated with Grade II and Grade III tumours.