Genomic and clinical‑pathological features of mucinous cystadenocarcinoma of the breast with HER2 amplification: A case report

Mucinous cystadenocarcinoma (MCA) of the breast is a rare, invasive carcinoma that resembles pancreatobiliary or ovarian MCA in terms of histological appearance. Most cases of MCA of the breast are negative for the estrogen receptor, progesterone receptor and ERBB2 (HER2). To the best of our knowledge, only five reports of HER2-positive MCA cases have been reported in the English language, and no reports focusing on the molecular characteristics of HER2-positive MCAs have been published. In the present study, a rare case of a 64-year-old woman with HER2-positive MCA who underwent long-term follow-up without recurrence or distant metastasis is reported. In addition, a detailed analysis of the genomic characteristics of the tumor is provided.