Determination of T cell monoclonality in non-Hodgkin's lymphoma by frozen section immunohistology. The SWOG Central Repository Members.

Monoclonal antibodies (mAb) reactive with seven distinct T cell receptor (TcR) alpha/beta variable region (V) families have become available. We investigated the potential utility of these mAb to establish T cell clonality (restrictive expression of one single V region family type) by frozen section immunohistology. We studied 40 non-Hodgkin's lymphomas (NHL) previously classified, immunophenotypically and genotypically by the South Western Oncology Group (SWOG) as 20 B and 20 T cell NHL. Frozen sections of each neoplasm were immunostained with the following mAb: beta-V5a, beta-V5b, beta-V6a, beta-V8a, beta-V12a, alpha/beta-Va and alpha-V2a. The large atypical lymphocytes of 18 of 20 T cell NHL showed no reactivity with the seven V region family mAb and only two showed exclusive immunoreactivity (one with anti-alpha V2a and the other with anti-beta V6a). All large atypical B cells in the 20 B cell NHL were non-reactive with the V region family mAb and each of the 40 neoplasms disclosed no or a trace reactivity in small host T cells. The results show that clonality can be determined in only a small percentage of T cell NHL (Sensitivity 10%, specificity 100%). Therefore, until new mAb become available, genotypic analysis remains the most sensitive and reliable method to establish T cell clonality.