Small, Depressed-Type Early Colon Cancer Invading Shallow Submucosal Layer With Extensive Lymph Node Metastasis: A Case Report

Early colorectal cancers are defined as invasive tumors that are limited to the mucosal layer or submucosal layer (SM), regardless of the presence or absence of lymph node (LN) metastasis. The reported incidence of LN metastasis of SM1 colon cancers is 0 - 5.9%, but the incidence in SM2 and SM3 colon cancers could be as high as 11.3 - 25.0%, and risk factors for LN metastasis include depth of SM invasion, growth patterns (polypoid or non-polypoid), histological sub-classification (moderate or poor differentiation) and regional lymphatic and vascular invasion. Among colorectal cancers with non-polypoid growth, the malignant potential is higher for depressed, than polypoid types, even for small tumors. Herein, we describe a patient with small, depressed-type early colon cancer with extensive LN metastasis and superficial SM invasion (pSM 450 µm). Six courses of chemotherapy with mFOLFOX6 and bevacizumab reduced the size of the LN metastases, thus eliciting a partial response (PR) according to the response evaluation criteria in solid tumors (RECIST).