Tehran University of Medical Sciences Case Reports in Clinical Practice 2538-2683 10 6 2026 06 03 289 292 Dipak Thorat Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India. Somanath Malage Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India. Rahul R Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India. Ashish Singh Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India. 2026 04 21 2026 04 26 Left-sided gallbladder (LSGB) is an exceedingly rare congenital anomaly;the occurrence of malignancy in a left-sided gallbladder is even rarer, making this case particularly unique. To the best of our knowledge, this is the first reported case of malignancy in an LSGB. A 65-year-old male presented with a two-month history of right upper quadrant abdominal pain with no history of jaundice or weight loss. Ultrasound of the abdomen revealed a suspicious mass in the gallbladder. CT scan of the abdomen confirmed an LSGB with diffuse irregular enhancing thickening of the gallbladder walls in the region of the body and fundus, infiltrating segment III of the liver and forming a moderate-sized intrahepatic soft tissue lesion measuring 43*33 mm, with TNM stage T3N0. The patient’s blood investigations were within normal limits, with CA 19.9 levels at 70 U/ml. The patient underwent staging laparoscopy and open extended cholecystectomy, which involved resecting the gallbladder along with a 3 cm wedge of liver (segments III, IVb) with clear gross margins, along with lymphadenectomy of stations 8, 9, 12, 13, and the right side of station 9. The patient had an uneventful postoperative recovery and was discharged on postoperative day 4. Histopathological examination revealed a pT3N0 (0/16) poorly differentiated adenocarcinoma with clear margins. The patient received adjuvant chemotherapy with 6 cycles of capecitabine. At one-year follow-up, the patient was doing well with no evidence of recurrence. In conclusion, malignancy in a left-sided gallbladder is a very rare occurrence, this being the first case report of such a condition. Successful management requires a thorough knowledge of biliary and hepatic anatomy, good preoperative imaging work-up, and a tailored surgical approach to achieve optimal outcomes. https://crcp.tums.ac.ir/index.php/crcp/article/view/1179 https://crcp.tums.ac.ir/index.php/crcp/article/download/1179/766