Bone marrow and extramedullary variations of cell membrane antigen expression in childhood lymphoid neoplasias at relapse.

To increase our knowledge of the pathogenesis of tumour recurrence, cell membrane phenotypes were determined on bone marrow and extramedullary tumour cells at diagnosis and at relapse in 24 children with lymphoid malignancies. There were 19 patients with acute lymphoblastic leukemia and five with non-Hodgkin's lymphoma. Membrane characteristics used for classification were E-rosetting, T antigen, surface immunoglobulin (sIg) and Ia antigen. Twelve patients were phenotyped as non-T, non-B, five as T-like and seven as B-like leukemia/lymphoma. Eighty-eight tissue samples were assayed for cell surface markers at the time of relapse(s). Lymphoblasts from 18 children (75%) demonstrated no variation in membrane marker expression. Six patients (25%) showed alteration of antigen expression on lymphoblasts obtained during relapses. This was manifested by loss of Ia antigen in two patients, loss of E-rosetting in one patient and loss of sIgD in one patient. Lymphoblasts from two patients, initially non-reactive with the four membrane markers utilized, expressed Ia antigen on subsequent relapses. Despite these variations no patient was categorized differently (i.e. T-like becoming non-T, non-B). Simultaneous lymphoblast phenotype determination from multiple body sites in 13 children showed no variation in marker analysis. A lymphoblast's phenotype remains stable throughout repeated relapses and is not influenced by relapse site in most children with lymphoid neoplasias. This information may be helpful in designing protocols where cytotoxic monoclonal antibodies are used as a treatment modality in patients with recurrent disease.