Breast metastasis from pelvic high-grade serous adenocarcinoma: a report of two cases

BACKGROUND: Metastatic tumors to the breast reportedly account for 0.5% to 2.0% of all malignant breast diseases. Such metastatic tumors must be differentiated from primary breast cancer. Additionally, few reports have described metastases of gynecological cancers to the breast. We herein report two cases of metastasis of pelvic high-grade serous adenocarcinoma to the breast. CASE PRESENTATION: The first patient was a 57-year-old woman with a transverse colon obstruction. Colostomy was performed, but the cause of the obstruction was unknown. We found scattered white nodules disseminated throughout the abdominal cavity and intestinal surface. Follow-up contrast-enhanced computed tomography (CT) showed an enhanced nodule outside the right mammary gland. Core needle biopsy (CNB) of the right breast mass was conducted, and immunohistochemical staining of the mass suggested a high-grade serous carcinoma of female genital tract origin. We diagnosed the patient’s condition as breast and lymph node metastasis of a high-grade serous carcinoma of the female genital tract. After chemotherapy for stage IVB peritoneal cancer, tumor reduction surgery was performed. The second patient was a 71-year-old woman with a medical history of low anterior resection for rectal cancer at age 49, partial right thyroidectomy for follicular thyroid cancer at age 53, and left lower lung metastasis at age 57. Periodic follow-up CT showed peritoneal dissemination, cancerous peritonitis, and pericardial effusion, and the patient was considered to have a cancer of unknown primary origin. Contrast-enhanced CT showed an enhanced nodule in the left mammary gland with many enhanced nodules and peritoneal thickening in the abdominal cavity. CNB of the left breast mass was conducted, and immunohistochemical staining of the mass suggested a high-grade serous carcinoma of female genital tract origin. After chemotherapy for stage IVB peritoneal cancer, tumor reduction surgery was performed. CONCLUSIONS: We experienced two rare cases of intramammary metastasis of high-grade serous carcinoma of female genital tract origin. CNB was useful for confirming the histological diagnosis of these cancers that had originated from other organs. A correct diagnosis of such breast tumors is important to ensure quick and appropriate treatment.