Asumi Iesato, Takaaki Oba, Mayu Ono, Toru Hanamura, Takayuki Watanabe, Tokiko Ito, Toshiharu Kanai, Kazuma Maeno, Katsuhiko Ishizaka, Hiroyuki Kitabatake, Daisuke Takeuchi, Akira Suzuki, Jun Nakayama, Ken-ichi Ito

It is occasionally difficult to diagnose breast metastasis of gastric carcinoma because of its rarity. However, to appropriately treat patients with breast tumors without delay, it is important to distinguish metastatic cancer from primary breast cancer. We report two cases of breast metastasis of gastric carcinoma and review the literature. The first case was a 41-year-old female diagnosed with bilateral pelvic tumors who visited the outpatient clinic because of pain and enlargement of both breasts. Ultrasonography showed diffuse hypoechoic lesions, which were enhanced on gadolinium-enhanced magnetic resonance imaging in the bilateral mammary gland. Core needle biopsy of the right breast revealed signet-ring cells, which were also identified in the resected bilateral pelvic tumors. Subsequent upper gastrointestinal endoscopy revealed signet-ring cell carcinoma in the stomach, and the bilateral breast lesions were diagnosed as metastases of gastric carcinoma. The second case was a 34-year-old female diagnosed with cervical metastasis of signet-ring cell carcinoma who was referred to the breast cancer clinic because of a nodule in the left breast detected by computed tomography. Ultrasonography showed a hypoechoic nodule that was enhanced on gadolinium-enhanced magnetic resonance imaging. Because the pathologic findings for the left breast nodule were quite similar to those of gastric cancer and its cervical metastasis, the breast nodule was diagnosed as a metastasis of gastric carcinoma. When a breast tumor is suspected to have metastasized from a primary tumor in another organ, particularly if signet-ring cells are found, the possibility that gastric cancer is present should be considered.