Synchronous Primary Gallbladder and Colon Adenocarcinoma: A Case Report and Systematic Literature Review.

Synchronous primary malignancies, defined as two or more primary malignancies diagnosed simultaneously or within six months, are uncommon and present unique diagnostic and therapeutic challenges. Synchronous primary adenocarcinoma of the gallbladder and colon is particularly rare. We report a case of a 48-year-old female presenting with persistent right upper abdominal pain. Laboratory tests and imaging studies initially suggested xanthogranulomatous cholecystitis. However, subsequent laparoscopic cholecystectomy and pathological examination revealed a moderately differentiated adenocarcinoma of the gallbladder (pT2bN1M0). Further staging with CT and PET-CT scans identified a suspicious mass in the transverse colon, confirmed by colonoscopy and surgical resection as well-differentiated adenocarcinoma of the transverse colon (pT3N0M0). Immunohistochemistry and genetic profiling of both tumors indicated distinct primary origins without loss of mismatch repair (MMR) protein expression. The patient underwent additional liver resection, lymph node dissection, and right extended hemicolectomy. She is currently undergoing further staging and awaiting chemotherapy. A review of English-language literature revealed eight reported cases of synchronous primary gallbladder and colorectal cancer and a total of 13 with synchronous primary malignancy of other organs. Such cases are rare and diagnostically complex cases. Common factors contributing to multiple primary malignancies (MPM) include genetic predispositions, previous cancer treatments, and lifestyle factors such as smoking and alcohol consumption. This case underscores the importance of thorough investigation and prompt treatment in patients suspected of having MPM. Advances in diagnostic imaging and molecular profiling are crucial for early detection and tailored therapeutic strategies. Standardized guidelines for managing synchronous cancers are needed to improve patient outcomes.