A case of gallbladder metastases with a different histologic type detected during lung cancer treatment.

A 47-year-old man undergoing follow-up for previously treated squamous cell carcinoma of the lung was found to have two masses in the gallbladder and a new pulmonary nodule in the left upper lobe, different from the original tumor. Imaging findings suggested gallbladder masses atypical for primary gallbladder cancer. Endoscopic ultrasound-guided tissue acquisition of a hepatoduodenal ligament lymph node adjacent to the gallbladder revealed small cell carcinoma, distinct from the previously diagnosed squamous cell carcinoma. A transbronchial lung cryobiopsy confirmed small cell lung carcinoma of the left upper lobe. Based on these findings, the patient was diagnosed with metachronous small cell lung carcinoma with gallbladder metastases. To our knowledge, this is the first reported case of gallbladder metastases from small cell lung carcinoma arising after prior treatment of squamous cell carcinoma in the same patient. This case highlights the importance of histopathological evaluation of new lesions, even in patients with a history of lung cancer, to ensure accurate diagnosis and treatment planning.