Immunophenotypic diagnosis of non-Hodgkin's lymphoma in paraffin sections. Co-expression of L60 (Leu-22) and L26 antigens correlates with malignant histologic findings

The recent availability of monoclonal antibodies immunoreactive to T- or B-lineage antigens in formalin-fixed, paraffin-embedded tissue has permitted the adaptation of frozen-section immunodiagnostic criteria to paraffin-embedded tissue. Among a variety of reactive lymphoid processes, monoclonal antibody L26 showed a pattern of staining consistent with pan-B reactivity. Antibodies L60 (Leu-22) and UCHL-1 showed a pan-T and T-subset pattern of reactivity, respectively. In benign processes, L26 and L60 (or UCHL-1) were not coexpressed. In contrast, among 77 B-lineage non-Hodgkin's lymphomas, 42% showed aberrant co-expression of L26 and L60. The L26⁺/L60⁺ phenotype was most common in small lymphocytic lymphomas (80%) but was also noted in one third of diffuse large cell lymphomas. Expression of UCHL-1 was not identified in B-lineage neoplasms but was found, along with L60, on four of five T-lineage lymphomas studied as controls. The authors conclude that the anomalous coexpression of L60 and L26 antigens is a unique feature of B-lineage lymphomas and can be used for the immunodiagnosis of these malignancies in routinely processed tissue.