Morphological consistency of desmoplastic reactions between the primary colorectal cancer lesion and associated metastatic lesions

Some preceding studies show that a desmoplastic reaction (DR) at the invasive front of a primary tumor (DR^primary) is a promising prognostic indicator, and its histologic classification is an independent prognostic factor in patients with colorectal cancer (CRC). Although DR is observed in metastatic lesions, such as those in lymph nodes (DR^LN) and the liver (DR^liver), the association between DR^primary and DR of metastatic lesions is unclear. We investigated whether DR^LN and DR^liver could be categorized in the same manner as DR^primary and examined the features and prognostic implications of DR^LN and DR^liver. In this study, we evaluated 363 patients with metastases to lymph nodes and 45 patients with synchronous liver metastases who underwent curative resection. DR^LN and DR^liver statuses were classified as mature, intermediate, or immature, based on keloid-like collagen and myxoid stroma appearances in the metastatic lesions. Overall, 109, 106, and 148 patients had mature, intermediate, and immature DR^LN, respectively; in total, 5, 21, and 19 patients had mature, intermediate, and immature DR^liver, respectively. DR^LN and DR^primary (spearman’s rho = 0.43, P < 0.0001) and DR^liver and DR^primary (spearman’s rho = 0.40, P = 0.0069) were each significantly correlated. The 5-year relapse-free survival (RFS) after surgery was 67.7% for mature/intermediate DR^LN and 52.9% for immature DR^LN; the 5-year RFS after hepatectomy was 11.5% for mature/intermediate DR^liver and 5.6% for immature DR^liver. In conclusion, DR^LN and DR^liver may be classified in the same manner as DR^primary; morphological consistency of DR was observed between primary and metastatic lesions.