CD8 expression in anaplastic large cell lymphoma correlates with noncommon morphologic variants and T-cell antigen expression suggesting biological differences with CD8-negative anaplastic large cell lymphoma

Anaplastic large cell lymphoma (ALCL) is a T-cell neoplasm characterized by uniformly strong CD30 expression and common absence of T-cell markers. Most ALCL cases express CD4, but a small subset of ALCL cases has been reported to express CD8. Little is known about the clinicopathologic and prognostic features of CD8+ ALCL. In this study, CD8 was assessed in 158 patients with systemic ALCL: CD8 was positive in 13 of 67 (19%) ALK+ and 13 of 91 (14%) ALK-negative neoplasms. In ALK+ ALCL, the CD8+ subgroup more often showed a noncommon morphologic pattern (69% vs 13%, P = .0001) and was more often positive for CD2 (100% vs 45%, P = .001), CD3 (92% vs 24%, P = .0001), and CD7 (100% vs. 39%, P = .002), but less frequently positive for CD25 (50% vs. 100%, P = .02). Patients with ALK+ ALCL and CD8+ neoplasms also had a higher relapse rate (82% vs 48%, P = .05) and more often underwent stem cell transplant (73% vs 36%, P = .04). CD8 expression did not correlate with patient overall survival or progression-free survival regardless of ALK status (all P > 0.05). We conclude that CD8+ ALCL cases appear to be biologically different from the more common CD8- negative ALCL cases. Our data suggest that CD8 positivity in ALK+ ALCL helps to identify a subset of patients more prone to relapse or more in need of stem cell transplant during their clinical course, although there was no impact on survival in this cohort. (C) 2020 Published by Elsevier Inc.