In case of neoplasm claims, it is important to make a decision of differentiating malignant and benign. In Korean insurance market, there are many insurance products that cover cancer. In the insurance claims adjustment, differentiation between malignant and benign is according to histologic findings. However there are many neoplasms of bad clinical course in spite of benign histopathologic classification. In this article; astrocytoma, thymoma, gastrointestinal stromal tumor, colonic intramucosal carcinoma, gastric high grade adenoma/dysplasia, carcinoid tumor, MALT lymphoma, revision of Korean Classification of Disease-6th edition, and bladder tumors are reviewed in terms of differentiation between malignant and benign in the insurance claims. It may be helpful for claims staff to review important neoplasms in terms of differentiation between malignant and benign.