Mammary adenoid cystic carcinoma presenting with Ductal carcinoma in situ and axillary lymph node metastasis.

Mammary adenoid cystic carcinoma (ACC) is extremely rare tumors, comprising <0.1% of all breast cancers. Moreover, lymph node metastasis is <2% of mammary ACC. Here, we report a case of 51-year-old female presented with painful mass on her left breast and left axillary lymph node enlargement. Core needle biopsy revealed invasive ductal carcinoma. Left lumpectomy and axillary lymph nodes dissections were performed. The final pathological report showed triple-negative mammary ACC arising with high grade ductal carcinoma in situ (DCIS) and axillary lymph node metastasis. Immunohistochemistry study is useful in confirming a diagnosis. Given the rarity of this cancer, natural history of disease is still not clearly understood. Complete surgical excision is the mainstay of treatment. To our best knowledge, mammary ACC presenting with DCIS and axillary lymph node metastasis has never been reported and should be considered in the differential diagnosis of breast cancers.