Polypoid lesions of the gallbladder are becoming an increasingly common incidental finding. It is very important to distinguish between a benign polyp and a malignant polyp because of the poor prognosis of gallbladder (GB) cancer, but the radiologic tools such as abdominal ultrasound (US) and computed tomography (CT) are not sufficient to distinguish between a benign polyp and a malignant polyp. Therefore, many researchers have attempted to identify the factors that can help in preoperative differentiation between a benign polyp and a malignant polyp.
Gall bladder polyp (GBP) is a well-known pre-malignant lesion. The size of GBP, patient’s age and presence of symptoms are the risk factors for GB cancer. GBPs of 10 to 12 mm in diameter have lower risk of malignancy compared to that in GBPs larger than 13 mm, which is similar to the risk of malignancy in GBPs smaller than 10 mm. The use of this surgical indication (GBPs larger than 13 mm GBP) can prevent 50% of unnecessary cholecystectomies without the risk of missing malignant GBPs. Our findings suggest that GBPs with a diameter of 10 to 12 mm in patients younger than 45 years of age old can be observed carefully.
Although the natural history of gallbladder polyps (GBPs) is not completely understood and most of the available studies are retrospective in nature, the well-known predictor of malignancy in GBPs is a size greater than 10 mm in diameter. However, when we applied the 10-mm size criterion for performing surgery, many polyps were found to be benign in a clinical setting. Most of the benign polyps had a size of 10 or 11 mm, and the incidence of these polyps is increasing as general medical examination is being universalized. Previous studies have shown that polyp size of more than 10 mm is associated with higher risk of developing malignancy; however so far, none of the studies have tried to differentiate between polyps of more than 10 mm in size for determining the incidence of malignancy.
Therefore, we analyzed the pathologically proven GBPs after cholecystectomy for 16 years at Samsung Medical Center to determine the relevance of the 10-mm size criterion.
METHODS
We collected data of patients who were confirmed to have GBPs through cholecystectomy at Samsung Medical Center between January 1997 and December 2012. Among the patients who underwent cholecystectomy for GBP, those with a definite evidence for malignancy such as adjacent organ invasion, metastasis on preoperative imaging studies, polyp larger than 20 mm, absence of preoperative imaging study results, and patients having gallstones were excluded. We retrospectively collected and analyzed information on patient’s clinical characteristics, symptoms, ultrasonographic findings, and blood laboratory tests.
RESULTS
A total of 836 patients who had undergone cholecystectomy were retrospectively analyzed. Seven hundred eighty patients (93%) had benign polyps, whereas 56 patients (7%) had malignant polyps. Of the 56 patients with malignancy, 4 patients (7%) had borderline GBP (10-12 mm) and a patient had small GBP (< 10 mm) with T2 stage. We conducted an ROC curve analysis to verify the 10-mm size criteria (AUC = 0.887, SD = 0.21, P < 0.001). In the ROC curve for polyp size and malignancy, sensitivity and specificity of the 10-mm size criterion was 98.2% and 19.6%, respectively. The specificity of the 11-mm and 12-mm size criteria was 44.6% and 56%, respectively, whereas the sensitivity of these two size criteria was similar. We defined the GBPs of 10 to 12 mm as a borderline-sized GBP, which were found in 411 patients (49%). In this group, there was a significant difference in age between patients with benign and malignant GBPs (47 years vs. 60 years, P < 0.05).
CONCLUSION
GBPs larger than 13 mm need immediate excision whereas for borderline-sized GBPs detected in young patients, careful medical observation can be a rational decision.