Medical verification of cancer diagnosis in insurance claims is a very important procedure in insurance administrations. Claims staffs are in need of medical experts' opinions about claim administration. This procedure is called medical claim review (MCR) and is composed of verification and advice. MCR verification evaluates the insured’s physical condition by medical records and compares it with product coverage. It is divided into assessment of living assurance benefit, verification of cancer, and assessment of the cause of death. Actually cancer verification of MCR is applicable to coding because the risk ratio in product development is usually coded data. There are some confusing neoplastic diseases in assessing the verification of cancer. This article reviews gastrointestinal stromal tumors (GIST) and mucosa-associated lymphoid tissue tumors (MALToma) of the stomach. The second most common group of stromal or mesenchymal neoplasms affecting the gastrointestinal tract is GIST. Nowadays there are many articles about the pathophysiology of GIST. However there are few confirmative theories except molecular cell biology of KIT mutation and some tyrosine kinase. Therefore, coding the GIST, which has previously been classified as an intermediate risk group according to NIH2001 criteria, for cancer verification of MCR is suitable for D37.1; neoplasm of uncertain or unknown behavior of digestive organs and the stomach. The gastrointestinal tract is the predominant site of extranodal non-Hodgkin's lymphomas. B-cell lymphomas of the MALT type, now called extranodal marginal zone B-cell lymphoma of MALT type in the REAL/WHO classification, are the most common primary gastric lymphomas worldwide. Its characteristics are as follows. First, it is different from traditional stomach cancers such as gastric adenocarcinoma. Second, the primary therapy of MALToma is the eradication of H. pylori by antibiotics and the remission rate is over 80%. Third, it has a different clinical course compared to traditional malignant lymphoma. Someone insisted that cancer verification is not possible for the above reasons. However, there have been findings on pathologic mechanism, and according to WHO classification, MALToma is classified into malignant B-cell lymphoma and it must be verified as malignancy in MCR.