Peritumoral B cells in primary colorectal cancer and synchronous liver metastases associate with longer survival

Abstract

Prognostic value of local B cells across nontumor colon mucosa (NM), primary colorectal cancer (pCRC), and its paired synchronous and metachronous liver metastases (LM) are currently under investigation. This retrospective, single-center, hypothesis-generating study aimed to characterize the spatial B cell distributions and their association with survival. Formalin-fixed paraffin-embedded (FFPE) tissue sections from NM, pCRC, and synchronous ( N  = 55) or metachronous ( N  = 44) LM were stained immunohistochemically for B cells using anti-CD20 antibodies. Densities of B cells were assessed in NM, tumor center (TC), inner margin (IM), outer margin (OM), and peritumor area (PT) from pCRC and LM by using the QuPath software and assessed as prognostic variables for overall survival (OS). Most B cells in NM were confined to mucosa-associated lymphoid aggregates (LAs), whereas the TC of pCRC showed significantly lower B cell density. In pCRC and LM, B cell–rich LAs were concentrated in the OM and PT but comprised less than 50% of the total B cell infiltrate. Higher B cell densities were observed in OM and PT vs. TC and IM of pCRC and LM in both groups. Higher B cell density was found in TC of pCRC vs. LM and in OM of LM vs. pCRC in both groups. High B cell densities in the entire PT region of pCRC and LM and in IM of LM, as well as scattered in the tissue, were associated with longer OS in synchronous group. High density of LAs themselves in pCRC and LM in the synchronous group was significantly associated with longer OS. High infiltration of both total and scattered B cells in pCRC and in synchronous LM correlated with improved OS. Further multicenter, prospective validation is required to determine its clinical utility.