Intracystic papillary carcinoma of the male breast: a case report

BACKGROUND: Intracystic papillary carcinoma (IPC) is defined as cancer that develops from the wall of a cyst in the breast. As breast cancer in men accounts for only 1% of all breast cancers, male IPC is an extremely rare form of the disease. The present case report examines IPC in a man, along with an in-depth literature discussion. CASE PRESENTATION: A 64-year-old Japanese man noticed a mass in the right breast and sought medical attention. An elastic and soft neoplastic 3-cm lesion was palpated in the right papilla. As a 1-cm solid tumor with a gradual rise from the cyst wall was confirmed within the cyst, vacuum-assisted biopsy (VAB) was performed on that site. Pathological examination of the biopsy revealed heterotypic cells with an enlarged oval nucleus forming dense papillary structures mainly of vascular connective tissue component. Contrast-enhanced computed tomography (CT) confirmed thickening of the wall that protruded outside the cyst. The preoperative diagnosis was right breast cancer (male IPC) TisN0M0 stage 0 luminal B-like. Total mastectomy and sentinel lymph node biopsy were performed. In the excised specimen, a 4.0-cm unilocular cyst was found, along with a 1-cm solid tumor with a gradual rise from the cyst wall. Pathological diagnosis of the resected specimen shared similar characteristics with the solid tumor in the cyst: notably, an oval nucleus with histologically clear nucleolus and fine granular chromatin, cylindrically shaped heterotypic cells, and the presence of basophilic cells in the papillary growth with a thin stem of fibrovasculature as the axis. Some invasion of tumor cells into the interstitium was confirmed. As such, the final diagnosis was right breast cancer (male IPC) T2N0M0 stage IIA luminal B-like. The expression of hormone receptor (ER and PgR) was high, and endocrine therapy was initiated postoperatively (20 mg/day tamoxifen). At the present time (3 months postoperation), there has not been any evidence of metastasis. CONCLUSIONS: We reported a rare case of an IPC in the male breast, along with a literature review.