S1619 Metastatic Lobular Carcinoma of the Breast Masquerading as Gallstone Disease

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Introduction: Elective cholecystectomy for symptomatic gallbladder disease is one of the most common surgical procedures. Traditionally, histopathological evaluation of the gallbladder is routinely performed for all gallbladder specimens. This practice can occasionally allow for detection of rare gallbladder pathology. Case Description/Methods: A 60-year-old female presented with a six-week history of recurrent, post-prandial right upper quadrant abdominal pain. She had used over-the-counter antacids without relief. At presentation her vitals signs were normal and abdominal exam was unremarkable. An abdominal ultrasound showed a thickened gallbladder, multiple gallstones and no sonographic Murphy’s sign (Figure 1). Intra-operative findings were significant for a densely fibrotic, thick-walled and distended gallbladder. Microscopic exam of the gallbladder wall revealed the muscularis propria infiltrated by a neoplastic lesion arranged in linear cords. The cystic duct resection margin was involved by tumor. IHC staining was positive for cytokeratin-7 and estrogen and progesterone receptors. The diagnosis of metastatic invasive lobular carcinoma of the breast was made. On further evaluation, the patient did not have any breast-related symptoms and had not had age-appropriate screening mammograms. Her breast exam revealed right upper outer quadrant nodularity and an ultrasound of the breast showed a right-sided ill-defined density measuring 9.8 x 12 x 9.7 mm found to be grade II infiltrating lobular carcinoma on biopsy. PET-CT and bone scan were negative for any other sites of metastasis and the patient was diagnosed with Stage 4 breast cancer with isolated metastasis to the gallbladder and cystic duct. After discussion of her case in tumor board, she was started on letrozole. On two-year telephone follow-up after the diagnosis, the patient was asymptomatic and verbally reported no evidence of recurrence on annual PET-CTs. Discussion: The risk of incidentally finding gallbladder metastasis is reported to be 4.8%, most commonly from skin, renal or stomach primary malignancies. Gallbladder metastasis from a breast primary is exceedingly rare especially when diagnosed prior to the diagnosis of the breast primary. Breast cancer, specially of the lobular subtype, can frequently present with GI metastasis. Our case report underscores the significance of careful histopathological examination of the gallbladder postoperatively, especially in older patients and macroscopically abnormal gallbladders.Figure 1.: Ultrasound Gallbladder | [A] Largest gallstone measuring 30.6 mm [B] Gallbladder wall thickness measuring 9.6 mm.

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