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Re: The decision criterion of histological mixed type in “T1/T2” gastric carcinoma‐comparison between TNM classification and Japanese classification of gastric cancer

We read the article by Shimizu et al. [1] in E-pub issue of Journal of Surgical Oncology with interest. The authors concluded that the presence of undifferentiated component in differentiated T1/T2 gastric cancer was associated with tumor progression and the decision criterion of histological mixed type would be the presence itself of undifferentiated component rather than the dominant pattern. It is very important how to describe and how to understand the mixed type of histology in gastric cancer. However, we have two concerns to point out in here. The first one is the selection of patients in their study. In the clinical point of view, decision making to choose treatment strategy is definitively different between T1 (even between T1a and T1b) and T2 cancer, mainly because of significant increase in probability of lymph node metastasis with advancement of T stage. T2 cancer has much more probability of lymph node metastasis than T1 cancer, and therefore, histological type is much less important to make decision of treatment strategy. Also, treatment decision can be completely different between T1a and T1b even though some aggressive gastroenterologists have widened their inclusion criteria of ESD [2]. We worried about that various T stage could contaminate the results. The second one is for the survival analysis. Shimizu et al. demonstrated that cancer-specific survival of the D > U group (differentiatedpredominant mixed type) was significantly poorer than that of the pure D group (no undifferentiated component) at Figure 1. This is also interesting and acceptable result. But, it is not enough to conclude that the decision criterion of histological mixed type would be better on the basis of the poorest histological component in TNM than on the basis of the predominant histological component in JCGC. If they want to say like that, the direct comparison of survival between D > U and D < U should also be provided.