Cluster Containing More Than 20 CD3-Positive Cells in Bone Marrow Biopsy Is a Candidate Prognostic Indicator in Peripheral T-Cell Lymphoma, Not Otherwise Specified

Assessment of bone marrow (BM) involvement in peripheral T-cell lymphoma, not otherwise specified (PTCL) is straightforward in cases of extensive involvement but difficult in cases of minimal to partial involvement. We evaluated the usefulness of CD3 as an immunohistochemical marker for assessing BM involvement in PTCL patients. BM biopsies of 92 PTCL patients were immunohistochemically stained for CD3, CD4, CD8, CD20, and CD56, and evaluated by two hematopathologists. CD3 positivity was graded according to the proportion of CD3-positive cells and the number of CD3-positive cells in a cluster. These criteria were used to determine the cut-offs at which significant differences in progression-free survival (PFS) and overall survival (OS) were observed. Multivariate analysis controlling the International Prognostic Index (IPI) score and its individual factors revealed that >20 CD3-positive cells in a cluster adversely affected PFS (relative risk [RR], 2.1; 95% confidence interval [CI], 1.0–4.3; P=0.047) and OS (RR, 2.4; 95% CI, 1.1–5.1; P=0.028) independent of IPI score. A cluster with >20 CD3-positive cells is a candidate indicator for BM involvement in PTCL.