IDO1 and breast carcinoma: Of the examined 96 excisional biopsies with a mammary carcinoma, 76 (79%) contained adjacent normal/non-neoplastic mammary gland, in which alveoli and intralobular ducts showed positive cytoplasmic immunostaining for IDO1 in 80–100% of lining luminal epithelial cells, whereas the myoepithelial cell layer was negative.