Breast metastasis of a gastric adenocarcinoma mimics primary breast lobular carcinoma, case report

The breast is an infrequent site of stomach cancer metastasis. It may prove very difficult to distinguish a stomach cancer metastasis to the breast from a primary gastric carcinoma based on clinical, endoscopic, radiological and only histopathological features. It is important to make this distinction as the basis of treatment, that usually can be done with systemic therapies rather than surgery.

Case report:

A 53-year-old white woman was referred to our hospital after abnormal findings in a routine mammogram check-up. Mammography shows a BI-RADS 5, the breast echography confirmed an irregular tumor compatible with the BI-RADS 5 Category, measuring 14,9 × 33 × 36,1 mm in the right breast. In the left breast was visualized a BI-RADS 4-Tumor measuring 10,2 × 8,8 × 9,8 mm. Afterwards it was performed the punch-biopsy. Histologically, the right and the left specimens were first described as a well differentiate invasive lobular mamma carcinoma with atypical cellular infiltrations. However, after hormone receptor tests with HER2 and CISH-Analysis, it was found to be a metastasis of a diffuse gastric adenocarcinoma for both specimens. Reviewing her medical history, the patient already suffers from a gastric carcinoma, that was treated with chemotherapy FLOT-protocol. The patient underwent surgery with complete resection of both masses.

Discussion:

Metastatic tumors generally have similar immunohistochemical characteristics to their primary tumors. Metastases from adenocarcinoma of the stomach express the skin markers CEA, CK7, and CK20, while ER and PgR are not expressed. Human epidermal growth factor receptor (HER2) is expressed in 20% of gastric cancers and is not specific to breast cancer.