Colorectal and gastric metastases from lobular breast cancer that resembled superficial neoplastic lesions.

Breast cancer is the most common malignancy in women and has a risk of late recurrence. We report a case of metastasis to the stomach and colon 23 years after surgery, with characteristic findings. A 74-year-old woman underwent breast cancer resection at the age of 51. At the time, no additional therapy was performed despite the histological diagnosis of invasive lobular carcinoma with lymph node metastasis. Upper gastrointestinal endoscopy, which was performed as a follow-up for her chronic gastritis, revealed multiple erosions. Histology revealed diffuse proliferation of signet ring cell-like atypical cells, that were positive for cytokeratin CAM5.2 and estrogen receptor. These findings suggested metastasis from the invasive lobular breast carcinoma. Positron-emission tomography revealed sternal and vertebral metastases. Colonoscopy also performed to screen for intestinal metastasis revealed several lesions that resembled hyperplastic polyps. Although these lesions were not strongly suspected of metastasis, histology surprisingly revealed the same findings as the gastric metastasis. This case involved gastric and colorectal superficial metastases that were synchronously detected 23 years after primary treatment. We report that early-stage colorectal metastasis may resemble hyperplastic polyps, and biopsy should always be considered in patients with a history of breast cancer, regardless of years elapsed since treatment.