Benign Lymphoid Aggregates in the Bone Marrow
K Naemi, RK Brynes, R Dhillon, X Zhao, S Rezk. University of California, Irvine School of Medicine, Orange, CA; Los Angeles County + USC Medical Center, Los Angeles, CA
Background: Benign lymphoid aggregates (BLAs) are seen in approximately 2% of bone marrow specimens. Certain criteria have been proposed to help distinguish between benign and malignant aggregates. Benign aggregates are usually small (<600μm), have distinct borders, and have a random non-paratrabecular location. A detailed description of the distribution patterns of B and T lymphocytes within BLAs has not been investigated.
Design: 136 cases of BLA-containing bone marrow specimens were identified in the pathology files at UCIMC between 1993 and 2009. Of these, 13 cases showed loss of the aggregates on deeper sections. The remaining cases were examined for correlation with various clinical features listed in table 1. A panel of immunostains (CD3, CD20, Bcl-6, CD23, and Ki-67) was performed on all cases. Other additional stains, flow cytometry, and gene rearrangement studies were performed on select cases. The aggregates were categorized based on size, location (paratrabecular or random), and distribution of B and T lymphocytes. Lymphoma cases with malignant aggregates were used for comparison.
Results: Table 1 illustrates the distribution patterns of B and T lymphocytes in relation to our preset variables. In 23 cases originally diagnosed as BLAs, a suspicion of malignancy was raised based on our morphologic criteria. Additional studies and follow-up of these patients confirmed lymphoma in 3 cases with results still pending on some cases.
|Total cases||Mostly T cells, T cells in the middle, or mixture of B and T cells||B cells in the middle, or mostly B cells|