Introduction: Apocrine carcinoma of the breast is rare, accounting for 0.3% to 1% of all mammary gland malignancies. The incidence of bilateral breast cancer has been reported to range from 0.3% to 12% of all breast cancers. Furthermore, the incidence of synchronous bilateral carcinoma of the breast (SBC) is reported to be 1.0% of all breast cancers, while the incidence of metachronous bilateral carcinoma (MBC) of the breast is reported to be 7% of all breast cancers. Metachronous bilateral noninvasive cancer is even rarer, and few such cases have been reported to date. Metachronous noninvasive apocrine carcinoma of the breast developing in the contralateral breast after surgical treatment for ductal carcinoma in situ is extremely rare and has not been reported to date. This is the first report. Case Report: The patient is a 73-year-old woman. A week ago, she noticed a lump in her left breast and visited the author’s clinic. The patient underwent right mastectomy and sentinel lymph node biopsy for right breast cancer five years ago. The histopathological result was ductal carcinoma in situ (papillary ductal carcinoma). After the subsequent five years without postoperative follow-up visits, she returned to the author’s clinic. On palpation, an elastic, hard mass approximately the size of 3.8-centimeter was palpable in the upper-outer quadrant and in the upper-inner quadrant of the left breast. Core needle biopsy (CNB) was performed. The results demonstrated apocrine breast cancer. More specifically, she had ductal cancer in situ (DCIS) with tumor cells showing apocrine features. Conclusion: Apocrine breast cancer is a rare disease, and metachronous bilateral noninvasive breast cancer is even rarer and has not been reported to date. Here, a rare case of apocrine carcinoma of the breast is reported.
Keiichi Takahashi (Sat,) studied this question.