Histopathology of low, intermediate, high-grade DCIS in woman and cat. Low-grade ductal carcinoma in situ (DCIS) in woman (A) and cat (B) with proliferation of monomorphous, small and relatively uniform epithelial cells with moderate and eosinophilic cytoplasm, oval nuclei, arranged to form regular cribriform spaces. HE. Bar = 10 μm. Intermediate-grade ductal carcinoma in situ (DCIS) in woman (C) and cat (D) with proliferation of pleomorphic cuboidal cells with moderate eosinophilic cytoplasm, oval to elongate nuclei, and single prominent nucleoli; micropapillary pattern. Central secretion, necrotic cell debris and periductal inflammatory reaction is depicted in the human intermediate-grade DCIS. HE. Bar = 10 μm. High-grade comedo ductal carcinoma in situ in woman (E) and cat (F) with solid proliferation of epithelial cells in a distended duct with central necrosis. Highly pleomorphic cuboidal to oval cells with abundant eosinophilic granular cytoplasm, round vescicular nuclei and prominent nucleoli. Lymphocytes and plasma cells infiltrate the periductal stroma. Bar = 10 μm.