Reactive Bone Marrow Plasmacytosis: An Update for the Modern Era

Abstract

Bone marrow (BM) polytypic plasmacytoses (PP) were characterized decades ago and found to be associated with neoplastic, autoimmune and liver diseases and infections. We sought to update the associated conditions and morphologic features of PP. We examined BM reports from 2011-2013 (n = 3,435) for cases with plasma cells (PCs) >2% by BM differential. Polytypic was defined by a kappa/lambda ratio of >=0.5 and 5 PCs), distribution, and nucleoli and associated findings. A chart review was performed. We collected 303 patients with plasmacytosis without atypia (8.8% of total BMs), of which 101 had light chain analysis performed, ages 27-88 years (median 58), 56 males and 45 females. PCs accounted for 2.2%-20% (median 4.0%) of the cellularity. 55/101 (54%) patients (pts) had an associated known neoplasm, including a history of myeloma (n = 12), myeloid neoplasm (19), lymphoma (17), and carcinoma/sarcoma (4). Associated diseases included: autoimmune (32/101; 32%); infections (22/101; 22%), most commonly HIV (n = 9); and liver disease (10/101; 9%), most commonly cirrhosis (5). 41/101 (41%) patients had multiple associated diseases. 12 PP pts had BMs performed for evaluation of monoclonal proteins. PCs were predominately interstitial in 44/95 (46%), perivascular in 17/95 (18%), and both perivascular and interstitial in 33/95 (35%) cases; clustering was present in 29/95 (30%) cases. 5 cases were aplastic. 26/95 (30%) cases had lymphoid aggregates, 6/95 cases (6%) had lipogranulomas, and 5/95 (5%) had fibrosis. 60/95 (63%) had PCs with small eosinophilic nucleoli. Plasmacytoses without atypia are present in ~10% of BMs evaluated at an academic center; PP are most commonly associated with neoplasms and autoimmune disorders; no new clinical or drug associations were identified. PCs were as high as 20% of the BM differential, with an interstitial distribution and commonly small eosinophilic nucleoli.