Patterns of immunoglobulin staining in paraffin-embedded malignant lymphomas.

The demonstration of immunoglobulin light chain restriction in paraffin-embedded B cell lymphomas is a capricious and difficult procedure that has been abandoned by many diagnostic laboratories. Using a combination of microwave antigen retrieval performed in a pressure cooker and proteolytic digestion with trypsin, we were able to demonstrate immunoglobulin light chain restriction in 66 B cell lymphomas comprising 25 follicular lymphomas, 29 diffuse large cell lymphomas, 6 small lymphocytic lymphomas, 2 mantle cell lymphomas, 1 nodal marginal zone lymphoma, 1 Burkitt lymphoma, 1 hairy cell leukemia, and 1 plasmacytoma. There was concordance of results in 13 cases in which flow cytometry immunoglobulin analyzes were performed. Perinuclear staining was demonstrated in all cases with dot-like staining of the Golgi present in 23 cases. Perinuclear staining occurred in combination with cytoplasmic staining in 12 cases and membrane staining in 8 cases with 12 lymphomas showing more than two patterns of staining.