Abstract
Breast cancer is the most common cancer affecting women worldwide and has a rising incidence. Important prognostic factors include size, grade and hormone receptor status of the primary tumours, regional node involvement and distant metastases. Lobular breast carcinoma accounts for 10% of invasive breast cancers and is the second most common type following ductal breast carcinoma. Lobular breast cancer is often diagnosed at a later stage owing to challenging detection on screening mammograms and/or ultrasounds.
Gallbladder involvement of distant breast metastases is very rare and is typically found in patients with terminally advanced disease. We present a rare case of solitary gallbladder metastasis from lobular breast carcinoma in a 76-year-old Caucasian female with no known history of breast cancer. Clinical presentation and imaging investigations were consistent with cholecystitis, prompting cholecystectomy. Histopathological examination confirmed chronic cholecystitis and metastatic lobular breast carcinoma. Subsequent investigations revealed invasive lobular breast carcinoma of the left breast but no nodal or systemic involvement.
Gallbladder involvement in metastatic breast carcinoma is mostly reported incidentally in patients who undergo cholecystectomy for biliary colic or cholecystitis. Our case demonstrates an incidental solitary gallbladder metastasis leading to the diagnosis of invasive lobular breast carcinoma. It highlights the challenges of diagnosing lobular breast cancer on conventional imaging.

Key words: metastatic lobular breast cancer, cholecystitis, gallbladder involvement in metastatic breast cancer, invasive lobular breast carcinoma