Endoscopic resection of undifferentiated-type gastric carcinoma: an extreme step to be restrained?

Abstract

minute submucosal invasive cancer less than 3 cm, all on condition that the tumor is histologically of the differentiated type.Criterion (b) was untouched for a long time because most studies failed to specify the category of undifferentiated type (UD-type) tumors free from nodal metastasis. UD-type adenocarcinomas mostly had an ulcer component and could metastasize regardless of size or depth. This does not mean that UD-type T1 tumors are oncologically more aggressive than D-type T1 tumors. The patients' survival is similar or even better in the UD-type as long as they are treated by gastrectomy with lymphadenectomy [4]. The potential of lymphatic invasion, however, seems higher in UD-type tumors, which makes ESD diffi cult.A suggestion was made in 2000 that UD-type intramucosal cancer less than 2 cm in size without an ulcer component or lymphatic-vascular capillary involvement might be suitable for ESD [2]. However, such tumors were so rare that it was only in 2009 that the authors completed a collection of 310 such cases (of 3,834 T1 tumors of UD-type) treated by surgery, found no lymph node metastasis, and thereby concluded the risk is nil, with a very narrow 95% confi dence interval, 0-0.96% [5].It seemed that the fi nal hurdle had been successfully crossed. Then two brief reports were submitted to this journal, each describing a case of lymph node metastasis from a UD-type tumor that satisfi ed the above criteria. The case reported by Nasu and colleagues in this issue [6] was a 13-mm IIc lesion with signet-ring cells spreading only in the superfi cial third of the mucosal layer. No ulcer, breakdown of muscularis mucosa, or submucosal fi brosis was seen. Five perigastric lymph nodes in the tumor drainage area contained signet-ring cell carcinoma. The second case, reported by Hirasawa and colleagues [7], in this issue as well, was also a 13-mm IIc lesion of poorly differentiated adenocarcinoma and signet-ring cell carcinoma. A large lymph node along Endoscopic mucosal resection (EMR) of gastric tumor was commenced in Japan in the 1970s to remove small superfi cial adenocarcinomas. Lymph node metastasis was the only limiting factor for EMR to be a curative treatment, and a number of studies were conducted using the surgical databases to specify gastric lesions that had never metastasized to the lymph nodes. All studies consistently showed that at least small differentiated (D-type) adenocarcinomas confi ned to the mucosal layer without ulceration were free from nodal metastasis.Because some safety margin was indispensable for a new procedure to be introduced in cancer therapy, the original indications of EMR were strictly limited to tiny tumors as described below. In the late 1990s an innovative new technique emerged using specially designed needle knives (endoscopic submucosal dissection, ESD) [1], which has dramatically changed the procedure of endoscopic resection. ESD enabled resection of large tumors or those having an ulcer component (more precisely, ESD was invented because of the necessity of resectin...