Triple-negative invasive lobular carcinoma presenting with synchronous gastric metastasis: A case report.

Triple-negative invasive lobular carcinoma (TN-ILC) is a rare and highly aggressive subtype of breast cancer. The development of gastric metastases in breast cancer is extremely rare and typically occurs several years after initial diagnosis. The present case report describes a 68-year-old postmenopausal female patient who presented with TN-ILC with gastric metastases at initial diagnosis. This metastatic pattern is very rare and is often mistaken for primary gastric cancer, which poses a notable diagnostic challenge. Imaging and histopathological analyses confirmed typical TN-ILC features (estrogen receptor negative, progesterone receptor negative and HER-2 1+ positive) and revealed diffuse metastases to the gastric wall, brain, bone, adrenal glands, pleura and lymph nodes. Gastric metastases from breast cancer were further confirmed by immunohistochemical studies, including for GATA binding protein 3, Villin and cytokeratin 7/20. It is noteworthy that the patient exhibited no gastrointestinal symptoms, which could have led to a missed diagnosis. The present case underscores the significance of a comprehensive evaluation in metastatic breast cancer.