Breast cystic hypersecretory duct carcinomas (CHDC), characterized by cystic dilatation of ducts, cysts filled with thyroid colloid-like eosinophilic material, and by micropapillary carcinomas in the epithelium lining the cyst, is a rare histological variant of intraductal carcinomas. CHDC is differentiated from cystic hypersecretory hyperplasia. It's clinical manifestations are similar to those of other intraductal carcinomas. CHDC has a low-grade behavior for many years, but can be invasive, with the potential for metastasis. The importance of CHDC is its differentiation from a variety of other lesions of the breast, both benign and malignant. Various differential diagnoses for CHDC include: fibrocystic changes of the breast with microcyst formation, juvenile papillomatosis, benign mucocele-like lesions, juvenile secretory carcinomas, mucin-producing colloid carcinomas and metastatic follicular thyroid carcinomas. Histochemical staining (PAS, alcian blue and mucicarmine) or immunoperoxidase studies (CEA, alpha-lactalbumin and thyroglobulin) may also helpful in differential diagnoses. We report a case of a cystic hypersecretory duct carcinoma (CHDC) of the breast, and present a review of the literature.