The prognostic value of tumor macroscopic morphology in colorectal cancer.

[BACKGROUND] This study aims to evaluate the prognostic value of tumor macroscopic morphology in colorectal cancer (CRC) and understand the molecular mechanism behind different tumor morphologies.

[METHODS] 642 eligible patients were enrolled in this study, including 335 patients in the prospective study and 307 patients in the retrospective study. CRCs were categorized into protruded, ulcerative, and infiltrative types according to our morphological classification, and their clinicopathological features and prognosis were analyzed. Furthermore, bulk RNA sequencing, single-cell RNA sequencing (scRNA-seq) and immunohistochemistry were performed to map the tumor microenvironment of different tumor morphologies.

[RESULTS] In the prospective cohort, CRC with infiltrative type were significantly associated with unfavorable clinicopathological characteristics and poor survival compared with ulcerative type and protruded type. Bulk RNA sequencing revealed that the infiltrative type correlated with higher expression of fibroblast activation protein-α (FAP), periostin and platelet endothelial cell adhesion molecule-1 (PECAM-1), which corresponded with elevated cell proportions of stromal cells and endothelial cells in scRNA-seq. Additionally, a retrospective cohort was conducted to assess the value of preoperative endoscopic morphology and radiological morphology, both independently associated with disease-free survival (DFS).

[CONCLUSION] We proposed a revised tumor macroscopic morphology classification system in CRC. The infiltrative type is associated with poorer clinical outcomes, characterized by increased cancer-associated fibroblast (CAF) infiltration and enhanced angiogenesis compared with other types. Importantly, when expanded to endoscopy and CT preoperatively, both endoscopic and radiological morphology can serve as preoperative predictors of DFS.