Aihara H, Tsutsumi Y, Ishikawa H. Extramedullary plasmacytoma of the thyroid, associated with follicular colonization and stromal deposition of polytypic immunoglobulins and major histocompatibility antigens. Possible categorization in MALT lymphoma.
ACTA PATHOLOGICA JAPONICA 1992;
42:672-83. [PMID:
1476063 DOI:
10.1111/j.1440-1827.1992.tb03050.x]
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Abstract
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.
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