Expression of bcl-2 protein in distinguishing benign from malignant lymphoid aggregates in bone marrow biopsies.

In this study, the immunohistochemical expression of bcl-2 protein in benign and malignant lymphoid aggregates in bone marrow biopsies was investigated in order to estimate its significance in distinguishing the biologic nature of the aggregates. Paraffin-embedded tissues of 46 bone marrow biopsies were stained with a monoclonal antibody to bcl-2 protein using the supersensitive streptavidin biotin immunoperoxidase method after a microwave heating of the sections. Bcl-2 protein immunoreactivity was observed in various proportions of lymphoid cells in both reactive and malignant lymphoid bone marrow aggregates. The percentage of bcl-2 positive cells in malignant aggregates was substantially higher (mean value 78%) than that observed in reactive nodules (mean value 60%). The presence of bcl-2 protein has been confirmed both in malignant and benign bone marrow lymphoid aggregates. Thus, the bcl-2 protein expression should not be used as a discriminating criterion for the malignant nature of lymphoid aggregates.