Metastatic Gallbladder Cancer Masquerading as Primary Colon Malignancy

Abstract

We report a 69-year-old female with personal history of gallbladder cancer who was referred to our institution with a circumferential obstructing intra-luminal colonic mass that possessed pathological features common to both primary colorectal as well as gallbladder cancer, which posed a significant diagnostic and treatment challenge. This case reviews the method and rationale for arriving at the final diagnosis of gallbladder cancer metastasis and highlights the importance of modern molecular diagnostics as well as close communication between the pathologist and surgeon in its process. demonstrated findings consistent with adenocarcinoma, low- grade invasion into peri-muscular soft tissue, and was positive for lymphovascular and perineural invasion. No lymph nodes were obtained. For reasons unclear to the authors, she did not undergo repeat laparotomy for radical resection given her stage II disease (T2NxMx) and was instead followed clinically. Seven months later, she was found to have developed a 1.6cm enhancing lesion in the left hepatic lobe and was started on systemic chemotherapy with gemcitabine and capecitabine for 1.5 years without biopsy confirmation. She did well on this treatment with radiographic resolution of the liver lesion until 1 month prior to presentation, when she developed abdominal pain. A colonoscopy was performed that revealed a clearly intra-luminal, large circumferential friable mass in the sigmoid colon with luminal narrowing that did not allow passage of the scope. The lesion was biopsied and tattooed. Pathological evaluation of the lesion revealed invasive moderately differentiated, mucinous adenocarcinoma. At this point the origin of the tumor was unclear and the differential diagnosis included primary colorectal versus metastatic gallbladder. The patient was