Evaluation of mucin expression patterns in gastric borderline (group III) lesions

Background Recommendations for diagnosis and treatment of gastric borderline (group III) lesions remain controversial. We examined mucin expression patterns in endoscopically resected and forceps biopsy samples. Methods Sixty-three gastric lesions were histopathologically identified as belonging to group III on the basis of an endoscopic forceps biopsy. All of the patients underwent endoscopic resection, and the lesions were classified into group A (final diagnosis, adenocarcinoma) or group B (final diagnosis, adenoma). Immunostaining for MUC2, MUC5AC, MUC6, and CD10 was performed and the mucin phenotype determined. An additional 26 forceps biopsy samples from the above 63 patients were similarly evaluated. Results The proportion of complete gastric (positive for MUC5AC and MUC6) plus gastric-predominant phenotypes was significantly higher in group A (58.0%) than in group B (18.7%) lesions (P < 0.05). The proportion of the complete intestinal (positive for MUC2 and CD10) phenotype was significantly higher in group B (68.8%) than in group A (19.4%) (P < 0.05). Similar results were also observed in the 26 forceps biopsy samples histopathologically diagnosed as group III lesions. The proportion of samples with a diffuse Ki-67 immunostaining pattern was significantly higher in group A than in group B (P < 0.05). p53 expression was significantly higher in group A (29.2%) than in group B (4.3%) (P < 0.05). Conclusions Immunostaining of forceps biopsy samples for the mucin phenotype may be helpful for diagnosing gastric borderline (group III) lesions.