Diffuse small cleaved-cell lymphoma: a heterogeneous disease with distinct immunobiologic subsets. 
Diffuse small cleaved-cell lymphoma (DSCL) is a relatively uncommon non-hodgkin's lymphoma (NHL) in the United States and has not been the subject of recent in-depth study of factors predictive of outcome.  It is unique among the NHL of intermediate grade because there is no evidence of a curable subset of patients.  To investigate whether any laboratory data might predict outcome, we studied 33 cases collected during a 12-year period and correlated morphology, immunohistochemistry, and serum lactate dehydrogenase (LDH) with clinical data and outcome.  We found that proliferative rate (Ki-67), cell lineage (T v B cell), and serum LDH were associated with significant differences in survival.  A Ki-67 value greater than or equal to 20% was associated with a median survival of 20 months compared with 80 months for lower values (P = .0002); patients with tumors of T-cell lineage had a median survival of 20 months compared with 40 months for those with B-cell neoplasms (P = .0143); and a serum LDH greater than 225 IU/L was associated with a median survival of 8 months compared with 40 months for lower LDH levels (P = .0004).  Blastoid morphology was also linked to a trend toward poor outcome (P = .08).  Neither a history of low-grade lymphoma nor the presence of residual immunologically detectable follicles influenced outcome (P = .93 and .97, respectively).  We conclude that high Ki-67, high LDH, and T-cell lineage each identify DSCL patients with poor outcome.