Risk of lymph node metastases from intramucosal gastric cancer in relation to histological types: how to manage the mixed histological type for endoscopic submucosal dissection

Abstract

Background The behavior of early gastric cancer (EGC) with mixed-type histology (differentiated and undifferentiated) is incompletely understood. This study aimed to clarify the clinicopathological features of EGC with mixedtype histology in relation to lymph node (LN) metastasis. Methods Clinicopathological data from 410 patients who underwent surgical resection for intramucosal EGC were reviewed. Lesions were classified into four types according to the proportion of differentiated and undifferentiated components at histopathology: pure differentiated (PD) type, mixed predominantly differentiated (MD) type, mixed predominantly undifferentiated (MU) type, and pure undifferentiated (PU) type. We examined the clinicopathological differences between PD and MD, and between PU and MU, and the rate of LN metastasis according to tumor size and ulceration.Results Moderately differentiated adenocarcinoma was the primary component in MD relative to PD (90.7 vs. 46.1 %). Signet ring cell carcinoma was the main component in PU relative to MU (81.5 vs. 33.3 %). LN metastasis was more common in MU than PU (19.0 vs. 6.0 %). For intramucosal tumors larger than 20 mm without lymphovascular invasion and without ulceration, the rate of LN metastasis was 0 % for MD and 24 % for MU. For intramucosal lesions less than 30 mm with ulceration but without lymphovascular invasion, the rate of LN metastasis was 0 % for MD and 20 % for MU. Conclusions Histologically mixed-type EGC with a predominantly undifferentiated component should be managed as an undifferentiated-type tumor. Further investigation is required to determine whether mixed-type EGC with a predominantly differentiated component could be managed the same way as a differentiated-type EGC.

Incidence of lymph node metastasis in intramucosal gastric cancer measuring 30 mm or less, with ulceration; mixed, predominantly differentiated-type histology; and no lymphovascular invasion: a multicenter retrospective study

“…The most common histology patterns of mixed, predominantly differentiated-type tumors in our previous single-center study [7] were tub2 ? por (57 %; 30 of 53 cases) and tub2 ?…”

“…ESD, which is a newly developed and widely applied technique at present, allows a larger lesion to be completely resected with one entire specimen and hence enables more detailed histopathological evaluation. Our previous study evaluated clinicopathological differences between a pure differentiated type (differentiated adenocarcinoma alone) and a mixed, predominantly differentiated type (combination of differentiated adenocarcinoma and undifferentiated adenocarcinoma), and concluded that the frequency of lymph node metastasis was significantly greater for the mixed, predominantly differentiated type than for the well-differentiated type [7]. On the basis of these findings, a distinction should be made between the pure differentiated type and the mixed, predominantly differentiated type.…”

“…ESD enables the complete removal of large lesions, in contrast to endoscopic mucosal resection (EMR), and hence allows detailed histopathological evaluation [5]. However, the optimal treatment strategy for a tumor with mixed histology remains in question [6,7]. In contrast to the WHO Classification of Tumours of the Digestive System [8], the Japanese Classification of Gastric Carcinoma [9] has long adopted the policy that histological type is determined by its predominant component.…”

Outcomes of endoscopic submucosal dissection for differentiated-type early gastric cancer with histological heterogeneity

“…For EGC with submucosal invasion, Mita and Shimoda [4] and Hanaoka et al [5] reported that the rate of LN metastasis was higher in MUC-EGC than in PuD-EGC (27.4 % versus 7.0 % and 19.2 % versus 5.4 %, respectively). For EGC confined within the mucosal layer, Takizawa et al [6] also reported that the rate of LN metastasis was higher in MUC-EGC compared to PuD-EGC (11.1 % versus 3.1 %). However, no cases of LN metastasis were observed in either of these studies [4][5][6], if MUC-EGC met the curative endoscopic resection criteria for tumors of absolute or expanded indications proposed by the Japanese Gastric Cancer Association [1,2,7].…”

“…For EGC confined within the mucosal layer, Takizawa et al [6] also reported that the rate of LN metastasis was higher in MUC-EGC compared to PuD-EGC (11.1 % versus 3.1 %). However, no cases of LN metastasis were observed in either of these studies [4][5][6], if MUC-EGC met the curative endoscopic resection criteria for tumors of absolute or expanded indications proposed by the Japanese Gastric Cancer Association [1,2,7]. These consistent results from surgical series showed the minimal risk of LN metastasis in MUC-EGC cases meeting the curative endoscopic resection criteria for tumors of absolute or expanded indications and suggested that ESD might be indicated for these cases [4][5][6].…”