Background: CUP (Cancer of Unknown Primary) represents a frequent cancer type causing incomparable difficulties in pathological diagnosis as compared to other tumor types. To explore and analyze the causes of CUP (Cancer of Unkown Primary) patients with misdiagnosis in patients after laparoscopic cholecystectomy with cholecystitis or cholecystolithiasis. Methods: 13 patients with CUP (Cancer of Unkown Primary) were recruited in this research, who accepted the multidisciplinary discussion of the CMUP (Cancer of Multiple or Unknown Primary) multidisciplinary team. Our team analyzed the clinical data and pathological characteristics of these patients, and tried to find the common characteristics of the CUP patients whose primary site is the gallbladder that has been already removed. Results: 13 patients were received laparoscopic cholecystectomy because of previously considered cholecystitis or cholecystolithiasis. The gallbladder is considered as the primary organ supported by the pathological features of the metastatic sites. Importantly, all these patients have local abdominal wall and/or local perigallbladder lymph node metastases. Among them, 3 cases were diagnosed as gallbladder cancer, and 1 case was considered as high-grade intraepithelial neoplasia after pathological consultation, which were recognized as benign disease. Among the 13 cases, 9 cases showed local thickening of the gallbladder wall by preoperative CT or B-ultrasound. The median recurrence time was 16.4 months (9-48 months). Of the 13 patients, 5 received radical resection again, and received GP (gemcitabine plus platinum) chemotherapy after surgery. Of the 8 patients who were unable to undergo radical surgery, 5 received first-line GP based chemotherapy, 2 received first-line PD-1 immunotherapy combined with anti-vascular targeted drugs, and 1 received tegafur monotherapy due to poor physical condition. Till now, these patients are still under follow-up. Conclusions: Unexpected gallbladder cancer is the source of some unknown primary cancers. For these patients with cholecystitis or cholecystolithiasis, B-ultrasound examination should not be performed alone, and CT or MRI examination should be performed when necessary. We should pay high attention to the patients with cholecystitis or gallstone thickening of the gallbladder wall or other high-risk gallbladder cancer. Before surgery, clinical data should be analyzed comprehensively, and rapid frozen examination should be performed on patients suspected of having cancer. In order to avoid misdiagnosis, we should pay attention to the principle of none tumor and avoid the risk of incision implantation. If unexpected gallbladder cancer is found, radical operation should be performed as soon as possible.