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Mammary secretory carcinoma , also termed secretory carcinoma of the breast, is a rare form of the breast cancers. MSC usually affects women but in a significant percentage of cases also occurs in men and children. Indeed, McDvitt and Stewart first described MSC in 1966 and termed it juvenile breast carcinoma because an increased number of cases were at that time diagnosed in juvenile females. MSC is the most common form of breast cancer in children, representing 80% of childhood breast cancers, although it accounts for less than 0.15% of all breast cancers.
In 1980, Tavaosoli and Norris renamed juvenile breast carcinoma as "secretory carcinoma of the breast" based on its characteristic microscopic appearance of having eosinophilic extracellular secretions when its tissues were stained with the H&E stain. MSC has sometimes been termed secretory carcinoma without reference to its breast cancer location. However, the term secretory carcinoma has also been used to name tumors with the microscopic appearance of MSC that are localized in the salivary glands , thyroid gland , or skin. Mammary secretory carcinoma is used here to distinguish it from these formerly termed secretory carcinomas.
MSCs typically develop as ductal breast tumors that have invaded the tissue around their ducts of origin, may have spread to nearby sentinel lymph nodes or axillary lymph nodes but have rarely metastasized to distant tissues. They are usually small, slow-growing, painless, well-circumscribed, movable breast masses. MSC tumors typically have distinctive microscopic features and tumor cells that carry a characteristic genetic abnormality that appears to underlie their development and/or progression.
Surgical removal has been considered the mainstay of treatment for localized MSCs tumors. The rare cases of MSC tumors that have metastasized to distal tissues have been treated with chemotherapy and radiation therapy but have shown little to no responses to these treatments. Emerging studies suggest that drug therapy targeted at the genetic abnormality in MSC tumor cells may be a more effective treatment for the latter tumors.