LUM and neoplasm: Lumican has been proposed to have a tumor suppressor function by preventing the activation of the TGFB2/Smad2 signaling pathway, which results in less cell adhesion and loss of inhibition of cell proliferation.36,41,42 One of the most frequently mutated genes in MSI tumors is TGFBR2, which encodes a receptor of TGFB2.43 Possibly the effects of lumican on the TGFB2/Smad2 pathway are redundant in tumors with a mutation in TGFBR2, which could explain the lack of prognostic value of lumican expression for patients with MSI tumors.