Feline breast carcinoma has aggressive and invasive behavior, with biological characteristics to breast cancer in women. This paper aims to identify how collagen type I and III forms in normal breast and in grouped carcinomas according to histopathological grading. The kurtosis attribute was the most representative to quantify the numeric stromal density. Results suggest that the gain of reticular fibers occurs both in the portion of higher biological activity (periphery) and in the center.