Gastric Metastasis from Invasive Lobular Breast Cancer, Resembling Primary Gastric Cancer

Invasive lobular carcinoma (ILC) is the second most common subtype of invasive breast cancer and sometimes presents with an unusual metastatic pattern. Its gastric metastasis is difficult to differentiate from primary adenocarcinoma. This report presents a case of breast ILC for which the initial presentation was gastric metastasis. A 62 -y -old woman presented with gastric outlet obstruction secondary to a gastric mass that had been diagnosed on upper gastrointestinal endoscopy and biopsy. The patient had been referred for 18F-FDG PET/CT for staging. The baseline 18F-FDG PET/CT scan demonstrated extensive axillary nodal and gastric metastases with a breast mass, which raised suspicion of a primary breast carcinoma. Distinguishing primary gastric adenocarcinoma from metastatic breast ILC is essential, considering that the 2 diagnoses lead to divergent treatments. Therefore, this entity needs to be considered in the differential diagnosis in clinical practice.