Objectives This study aims to analyze and explore the cases with C76 codes in a hospital,find the wrong codes and summarize the reasons,so as to improve the coding accuracy rate.Methods 306 discharged medical records from a hospital from 2013 to 2022 with disease codes including C76 were retrieved.Based on the ICD-10 classification principles,the C76 coding situation was checked case by case and the error rate was counted and analyzed.Results Among 306 medical records,the coders'disease coding error rate was 98.69%.Among them,81.79%of the errors were caused by the coders'failure to search for codes according to the tumor coding principles,13.24%of the errors caused by the coders'insufficient basic knowledge of clinical medicine,and 4.97%of the errors caused by unclear diagnosis by doctors.Conclusions The main reasons leading to the misclassification of disease coding as C76 were due to the coders'failure to follow the rules of oncology coding as well as their failure to carefully review the pathology reports.Hence,coders should enhance their comprehensive skills,establish effective communication channels with clinicians,and enhance departmental quality control efforts to improve coding accuracy effectively.