Background: Long-term clinical outcomes after endoscopic submucosal dissection (ESD) is unclear for differentiated-type-predominant early gastric cancer (EGC) mixed with undifferentiated component (MUC-EGC). Therefore, the role and appropriate indication of ESD for MUC-EGC remain to be evaluated.
Methods: Between 2007 and 2011, 1,577 differentiated-type EGC lesions [1,408 pure differentiated-type (PuD)-EGCs and 169 MUC-EGCs] in 1,527 consecutive patients were treated by ESD. After ESD, MUC-EGC was managed in the same way as PuD-EGC. The clinicopathological features and long-term outcomes after ESD of MUC-EGC were compared with those of PuD-EGC.
Results: En bloc resection and en bloc with R0 resection rates in MUC-EGC cases were 94.1 % and 81.7 %, respectively. MUC-EGC was significantly associated with larger tumor size, more frequent submucosal invasion, and lymphovascular invasion compared to PuD-EGC. Despite these aggressive features of MUC-EGC, no lymph node metastasis or extragastric recurrence occurred during follow-up after ESD if MUC-EGC met the curative endoscopic resection (ER) criteria for tumors of absolute or expanded indications. Four MUC-EGC cases meeting the curative ER criteria underwent additional radical gastrectomy after ESD, and no case showed lymph node metastasis. During a median 48 months of follow-up, overall survival rates for MUC-EGC meeting the curative ER criteria for tumors of absolute or expanded indications (3-year survival rates, 100 % and 100 %) were comparable to those of PuD-EGC.
Conclusions: Long-term outcomes after ESD were favorable for MUC-EGCs meeting the curative ER criteria for tumors of absolute or expanded indications. Therefore, ESD may be used as a promising treatment option for these cases.