Extramedullary plasmacytoma of the thyroid, associated with follicular colonization and stromal deposition of polytypic immunoglobulins and major histocompatibility antigens. Possible categorization in MALT lymphoma.
A 78-year-old woman complaining of a neck mass underwent right hemithyroidectomy. The 7 x 6 cm thyroid tumor consisted predominantly of mildly atypical, epithelial membrane antigen-positive plasma cells and scattered lymphoid follicles. Features of follicular colonization (plasma cell infiltration into germinal centers) were noted. Numerous CD45RO-positive reactive T cells and a smaller number of CD20-positive blast-like B cells were also distributed among the plasma cell infiltrate. IgG, kappa-type monoclonality with J-chain reactivity was identified in the plasma cells, including those in the lymphoid follicles. The association of pre-existing lymphocytic thyroiditis was confirmed histologically in the non-tumorous thyroid tissue. The tumor exhibited deposition of reticulin fiber-rich, amorphous eosinophilic substances, provoking pronounced foreign body reactions. The deposit, polytypically immunoreactive for immunoglobulin gamma-, mu-, kappa- and lambda-chains, beta 2-microglobulin and HLA-DR, was scarcely reactive upon amyloid staining, and consisted ultrastructurally of electron-dense, non-fibrillar material and entrapped collagen fibers. Multiple myeloma was ruled out by laboratory, histologic and clinical examinations. The possible categorization of this extramedullary plasmacytoma of the thyroid within low-grade B cell lymphoma of the mucosa-associated lymphoid tissue (MALT) is discussed.
Aihara
H
H
Department of Pathology, Tokai University School of Medicine, Kanagawa, Japan.
Tsutsumi
Y
Y
Ishikawa
H
H
D000368:Aged; D005260:Female; D006680:HLA Antigens / Q000032:analysis*; D006801:Humans; D007128:Immunoglobulin Fragments / Q000032:analysis*; D007142:Immunoglobulin gamma-Chains / Q000032:analysis; D007145:Immunoglobulin kappa-Chains / Q000032:analysis; D007146:Immunoglobulin lambda-Chains / Q000032:analysis*; D007148:Immunoglobulin mu-Chains / Q000032:analysis; D008221:Lymphoid Tissue / Q000276:immunology*; D016393:Lymphoma, B-Cell / Q000145:classification / Q000276:immunology / Q000473:pathology; D009092:Mucous Membrane / Q000737:chemistry / Q000276:immunology; D010954:Plasmacytoma / Q000145:classification / Q000276:immunology* / Q000473:pathology*; D013964:Thyroid Neoplasms / Q000145:classification / Q000276:immunology* / Q000473:pathology*; D001613:beta 2-Microglobulin / Q000032:analysis*
D006680:HLA Antigens; D007128:Immunoglobulin Fragments; D007142:Immunoglobulin gamma-Chains; D007145:Immunoglobulin kappa-Chains; D007146:Immunoglobulin lambda-Chains; D007148:Immunoglobulin mu-Chains; D001613:beta 2-Microglobulin