Mucinous Adenocarcinomas Histotype Can Also be a High-Risk Factor for Stage II Colorectal Cancer Patients

Background/Aims: Colorectal mucinous adenocarcinoma (MA) has been associated with a worse prognosis than adenocarcinoma (AD) in advanced stages. Little is known about the prognostic impact of a mucinous histotype on the early stages of colorectal cancer with negative lymph node (LN) metastasis. In contrast to the established prognostic factors such as T stage and grading, the histological subtype is not thought to contribute to the therapeutic outcome, although different subtypes can potentially represent different entities. In this study, we aimed to define the prognostic value of mucinous histology in colorectal cancer with negative LNs. Methods: Between 2006 and 2017, a total of 4893 consecutive patients without LN metastasis underwent radical surgery for primary colorectal cancer (MA and AD) in Fudan University Shanghai Cancer Center (FUSCC). Clinical, histopathological, and survival data were analyzed. Results: The incidence of MA was 11% in 4893 colorectal cancer patients without LN metastasis. The MA patients had a higher T category, a greater percentage of LN harvested, larger tumor size and worse grading than the AD patients (p < 0.001 for each). We found that MA histology was correlated with a poor prognosis in terms of relapse in node-negative patients, and MA histology combined with TNM staging may be a feasible method for predicting the relapse rate. Additionally, MA presented as a high-risk factor in patients with negative perineural or vascular invasion and well/moderate-differentiation and showed a more dismal prognosis for stage II patients. Meanwhile, the disease-free survival was identical in MA and AD patients after neo- and adjuvant chemotherapy. Conclusion: MA histology is an independent predictor of poor prognosis due to relapse in LN-negative colorectal cancer patients. Mucinous histology can suggest a possible high risk in early-stage colorectal carcinoma.