Ki-1-positive large cell lymphomas, a heterogenous group of neoplasms. Morphologic, immunophenotypic, genotypic, and clinical features of 24 cases.

Clinical and pathologic features of 24 patients with large cell lymphomas that expressed the activation antigen Ki-1 are described. Phenotypic and/or genotypic studies characterized these neoplasms as T-cell (16 cases), B-cell (six cases), or null cell (two cases) type. Males predominantly were affected. Age of patients ranged from 19 to 73 years, with a bimodal distribution, with peaks in the third and seventh decades. Lymphadenopathy was present in nearly all patients. Extranodal involvement, including skin, soft tissue, bone, central nervous system, lung, or small intestine was observed in a total of 54% of the patients, either at presentation or during the course of disease. "Prototypic" features of large cell anaplastic lymphomas were observed for eight T-cell lymphomas, with morphologic heterogeneity noted for the remainder. Eight patients, all with T-cell neoplasms (only one with prototypic morphology), have died of lymphoma (median survival, 5 months). An antecedent history of a lymphoproliferative disorder (mycosis fungoides, B-cell lymphoma, immunoblastic lymphadenopathy) was apparent in seven patients. An 8-year history of Crohn's disease occurred in one patient with a T-cell lymphoma involving small intestine. Phenotypically, loss of one or more markers was typically noted for T-cell neoplasms. Leukocyte common antigen was detected in all cases, although partial loss of immunoreactivity was noticed in some cases. Nearly all cases evaluated for Ia antigen or alpha-1-antichymotrysin were reactive. Eleven of 16 T-cell, two of six B-cell, and two null cell lymphomas expressed epithelial membrane antigen. Ki-1-positive large cell lymphomas are characterized by clinical, morphologic, and immunophenotypic heterogeneity.