2.2. Data Collection
squamous cell carcinoma antigen, tumor
TUMOR
Baseline clinicopathological information on the patients obtained from the hospital's medical records included the following serum tumor markers: carcinoembryonic antigen (CEA), glycoantigen 19-9 (CA19-9), glycoantigen 12-5 (CA12-5), glycoantigen 72-4 (CA72-4), glycoantigen 15-3 (CA15-3), alpha-fetoprotein (AFP), serum squamous cell carcinoma antigen (SCC), ferritin (FERR), cytokeratin 19 fragment cyfra21-1 (CYFRA21-1), serum neuron-specific enolase (NSE), pathological type, histological type, age, sex, location, diameters, number of sampled lymph nodes (LNs), number of positive LNs, T-stage, N-stage, M-stage, perineural invasion, and vascular invasion. MMR status was assessed by immunohistochemistry (IHC) and was determined by MSH2, MSH6, MLH1, and PMS2 markers. We defined dMMR as a lacking expression of one or more MMR proteins, while tumor with intact MMR proteins was categorized as pMMR.