Metastatic Invasive Lobular Carcinoma of Bilateral Breasts Presenting with an Abdominal Mass

Breast cancer remains the most frequent malignancy in women, with the two most common histological subtypes of breast cancer being the invasive ductal carcinomas (IDC) and invasive lobular carcinomas (ILC). The most common sites of breast cancer metastases are the liver, lung, pleura, brain and bone. Gastrointestinal, peritoneal, gynaecological and renal metastases are less common, often masquerading as primary malignancies and causing diagnostic confusion, mostly occurring in ILC as compared to IDC.

We report a case of a young woman presenting with an enlarging abdominal mass which was suspicious of a primary abdominal malignancy. Endoscopy and gastric biopsy revealed poorly differentiated carcinoma. On the top-most slices of her abdominal CT, bilateral enhancing breast lesions were detected, suspicious of metastases. Ultrasound and biopsy done for the breast lesions showed bilateral ILCs. Further staining of the gastric biopsy specimen confirmed the final diagnosis of gastric metastases from bilateral breast ILCs rather than a primary gastric tumour with breast metastases.

This case highlights how breast cancer metastases to the GI tract may mimic primary GI cancers as well as the importance of breast examination, family history, radiological and pathological examination in detecting the breast origin of advanced carcinomas. Awareness of the different patterns of metastatic spread of ILC and IDC is also important due to the infiltrating nature and nonspecific imaging findings of these tumours, requiring a high index of suspicion from the surgeons, oncologists, radiologists and pathologists.