Abstract
Benign lymphoid aggregates are seen in only a minority of bone marrow specimens, but their distinction from non-Hodgkin lymphoma, particularly B-cell lymphomas, can represent a diagnostic challenge. Although criteria have been proposed to help distinguish between benign and malignant aggregates, a detailed description of the distribution patterns of B and T lymphocytes within benign lymphoid aggregates has not been investigated. One hundred thirty-seven cases of bone marrow specimens containing benign aggregates were studied with a panel of immunostains. A subset of these cases was also examined for immunoglobulin gene rearrangements by polymerase chain reaction. The aggregates were categorized based on size, location (paratrabecular or random), presence of infiltrating edges, and distribution of lymphoid cell populations. In addition, we examined 40 cases of bone marrow biopsies with documented malignant lymphoid aggregates for comparison purposes. We report that the distribution of B and T lymphocytes within lymphoid aggregates may serve as a useful criterion to aid in the separation between benign and malignant aggregates. When aggregates exhibit a predominance of T cells, consist of a central core of T cells surrounded by a rim of B cells, or have a mixed distribution of B and T cells, they are more likely to be benign. On the other hand, an increased likelihood of malignancy occurs when aggregates exhibit a predominance of B cells or consist of a central core of B cells surrounded by a rim of T cells (excluding germinal center formation), and assessing other features worrisome of malignancy (large aggregate size, presence of infiltrative edges, cellular atypia, and paratrabecular location, among others) is warranted.
Highlights
Lymphoid aggregates, whether benign or malignant, are a relatively uncommon finding in bone marrow biopsy specimens
Benign lymphoid aggregates lymphoid aggregates, paratrabecular location, inclusion of fat cells, and location surrounding large sinuses are all features that have been reported to be worrisome for malignancy [2,3]
We examined BLA and associated clinical conditions; our primary goal was to study the distribution of lymphocyte populations within the aggregates and to determine if distribution patterns can aid in the distinction of neoplastic from benign aggregates
Summary
Whether benign or malignant, are a relatively uncommon finding in bone marrow biopsy specimens. BLAs have been reported to be associated with a variety of conditions including aging, autoimmune diseases, inflammatory conditions, and infectious disorders [1]. They have been reported to be commonly identified in patients with chronic myeloproliferative neoplasms, especially primary myelofibrosis [4] and, rarely, in association with myelodysplastic syndromes [5]. An increased incidence of benign aggregates in lymphoma patients who have been treated with rituximab has recently been reported [6,7] These aggregates are often found in postchemotherapy bone marrow specimens and can mimic residual lymphoma [7,8]. BLAs have been rarely reported in association with tobacco use and certain medications [9,10]
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