A 45-year-old woman with longstanding Hashimoto thyroiditis develops a thyroid lymphoma. Biopsy shows diffuse infiltration by medium-to-large B cells with a prominent lymphoepithelial lesion pattern, destroying thyroid follicles. Which lymphoma type is most common in this setting, and what is the typical immunophenotype?
- A Primary thyroid diffuse large B-cell lymphoma (DLBCL), arising from MALT lymphoma background; CD20+, BCL-6+, MUM1 variable, CD10 usually negative
- B Mantle cell lymphoma of the thyroid; CD20+, CD5+, cyclin D1+ (BCL-1) due to t(11;14)
- C Extranodal marginal zone lymphoma of MALT type (MALT lymphoma); CD20+, CD5-, CD10-, BCL-6-, cyclin D1- ✓
- D Follicular lymphoma of the thyroid; CD20+, CD10+, BCL-2+, BCL-6+, t(14;18)
Explanation
Primary thyroid lymphoma most commonly arises as extranodal marginal zone lymphoma of MALT type on the background of chronic autoimmune thyroiditis (Hashimoto disease). The biopsy shows lymphoepithelial lesions (neoplastic lymphocytes infiltrating and destroying follicular epithelium) — the hallmark of MALT lymphoma. MALT lymphoma immunophenotype: CD20+, surface Ig+, CD5-, CD10-, BCL-6-, cyclin D1- (distinguishing it from mantle cell). DLBCL also occurs in the thyroid (sometimes arising from MALT transformation) and is then CD20+ with BCL-6/MUM1 expression. The specific lymphoepithelial lesion pattern and indolent CD5-/CD10- phenotype defines MALT.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
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Written and medically reviewed by the StethoPrep medical team.