An IgA plasmacytoma: a rare and distinct form of plasmacytoma

An IgA plasmacytoma: a rare and distinct form of plasmacytoma
Author: Huan-You Wang; Aaron M. Goodman
Category: Lymphoma: Mature B-cell and Plasma cell Neoplasms > Plasma Cell Neoplasm > Plasmacytoma > Extraosseous plasmacytoma
Published Date: 05/01/2020

The patient, a 40-year-old healthy man with no past medical history, presented with asymptomatic bilateral enlarged cervical lymph nodes (LNs) of 3 months’ duration. Cross-sectional positron emission tomography/computed tomography revealed supraclavicular, hilar, mediastinal, and axillary LN enlargement; the largest one measured 1.9 cm. Hematoxylin and eosin staining of the resected left cervical LN revealed that the nodal architecture was partially effaced by a well-demarcated large nodule composed of sheets of mature plasma cells (PCs) (panel A, original magnification ×200). These PCs were positive for CD19 (dim) (panel B, original magnification ×200), CD45 (data not shown), λ (panel C, original magnification ×200), and immunoglobulin A (IgA) (panel D, original magnification ×200) but negative for BCL1, CD20, CD56, CD117, Epstein-Barr virus, human herpesvirus-8, IgG, IgM, and κ (data not shown). Next-generation sequencing revealed TET2 mutation (T625fs*11). A bone marrow biopsy 4 weeks later showed a normal cellular marrow with no monotypic PCs. Multiple serum protein electrophoresis and immunofixation from at the time of LN biopsy to December of 2019 revealed a normal κ/λ free light chain ratio and no paraprotein, respectively. Taken together, this is an IgA plasmacytoma, a recently reported indolent and distinct form of extramedullary plasmacytoma.Recognizing this form of plasmacytoma is of paramount importance to avoid unnecessary treatment. As in this case, the patient remains asymptomatic with no progression of disease after follow-up for 29 months.