The diagnosis of noninvasive papillary tumors begins with categorization of the lesions as macropapillary or micropapillary. Macropapillary lesions include papilloma, papillary carcinoma, and papilloma harboring carcinoma. Papillomas consist of a few broad fronds, abundant stroma, and an epithelium containing both luminal and myoepithelial cells. Papillary carcinomas have many irregular fronds, small amounts of stroma, and a uniform population of malignant glandular cells. Papillomas can give rise to both conventional ductal hyperplasia and carcinomas. One analyzes proliferations on the surface of a papilloma as one would analyze those in a duct. Proliferations within the stalk of a papilloma require especially careful attention; one must observe large masses of cells demonstrating both cytological and architectural atypicality and devoid of intervening stroma to make the diagnosis of low-grade ductal carcinoma in-situ involving the stalk of a papilloma. Micropapillary proliferations represent either ductal hyperplasia or ductal carcinoma in situ. The former shows slight dilatation of ducts, micropapillae of similar size and shape, maturation of cells, lack of dishesion and necrosis, and lack of cytological atypicality. Micropapillary ductal carcinoma in situ exhibits extreme dilatation of ducts and lobules, micropapillae varying in size and shape, lack of maturation, dishesion and necrosis, and cytological atypicality.