Intralymphatic Spread is a Rare Finding Associated with Poor Prognosis in Diffuse Large B-Cell Lymphoma with Extranodal Involvements

Intralymphatic spread is common in solid cancers, but has been rarely studied in lymphomas. Review of 635 extranodal specimens from 475 diffuse large B-cell lymphoma (DLBCL) patients revealed intralymphatic spread in 10 surgical resection specimens from 10 patients including 9 de novo DLBCLs and 1 Richter transformation. The prevalence in de novo DLBCL with extranodal involvements was 1.65%. The most common involved site of intralymphatic spread was the gastrointestinal tract, followed by the female genital tract and breasts. Lymphatic vessels, lined by D2-40-positive endothelial cells, were expanded by lymphoma cells, reminiscent of intravascular lymphoma or tumor emboli. None of the involved lymphatic vessels were located in the mucosa. Patients with intralymphatic spread had a trend of lower overall response rate and a trend of higher progressive disease than those without intralymphatic spread. Compared with patients without intralymphatic spread, those patients with intralymphatic spread had a shorter median overall survival (14.3 vs. 96.2 mo; P=0.004) and a shorter median progression-free survival (11.2 vs. 64.2 mo; P=0.01), respectively. Multivariate analyses showed that intralymphatic spread was an independent poor prognostic factor for overall survival (hazard ratio, 3.029; 95% confidence interval, 1.315-6.978; P=0.009), irrespective of the National Comprehensive Cancer Network-International Prognostic Index, B symptoms, and serum albumin levels. Among patients who underwent surgical resection, intralymphatic spread was still an independent prognostic factor. In conclusion, our study demonstrated extranodal intralymphatic spread in DLBCL. Inspiringly, this rare morphologic finding may serve as a new negative prognostic indicator in DLBCL with extranodal involvements.