Nodal large B-cell lymphoma with intrasinusoidal growth: a clinicopathologic study of a distinctive pattern with diagnostic overlap with intravascular large B-cell lymphoma.

Large B-cell lymphoma (LBCL) can show luminal growth in lymph nodes and extranodal sites, but nodal cases with intrasinusoidal growth may be difficult to distinguish from intravascular LBCL (IVLBCL). We retrospectively reviewed 19 LBCLs with luminal growth and classified them as nodal LBCL with intrasinusoidal growth (LBCL-IS; n = 5), extranodal LBCL with intravascular growth without hemophagocytic lymphohistiocytosis (HLH; n = 9), or extranodal LBCL with intravascular growth and HLH (n = 5). Compared with combined extranodal cases, nodal LBCL-IS was associated with older age (>75 years, 80.0% vs 14.3%; P = .024), fewer B symptoms (2/5 vs 12/13 evaluable cases; P = .044), absence of bone marrow involvement (0% vs 64.3%; P = .033), and lower serum lactate dehydrogenase levels (median, 327 vs 826 IU/L; P = .006). Limited-stage disease and low or low-intermediate International Prognostic Index scores occurred only in nodal LBCL-IS. Nodal cases largely shared a non-germinal center B-cell phenotype with extranodal cases, whereas Epstein-Barr virus positivity was confined to nodal LBCL-IS (2/5, 40.0%). Among extranodal cases, CD5 expression was associated with a higher complete response rate after initial chemotherapy (7/7 vs 1/5; P = .010). All five patients with nodal LBCL-IS achieved complete response after initial rituximab-based chemotherapy. Nodal LBCL-IS also showed longer progression-free and overall survival than HLH-associated extranodal LBCL (P = .021 and P = .049, respectively), although the small cohort size warrants cautious interpretation. These findings suggest that, despite its histologic resemblance to IVLBCL, nodal LBCL-IS represents a distinctive nodal growth pattern whose recognition may be clinically important.