Primary thyroid lymphoma: Diagnosis of immunoglobulin heavy chain gene rearrangement with polymerase chain reaction in ultrasound-guided fine-needle aspiration

We present a ease of primary thyroid lymphoma coexisting with Hashimoto's t hyroiditis in a 75-year-old woman in whom B-cell lymphoma was substantiated based on the findings of immunophenotyping and polymerase chain reaction ( PCR) gene rearrangement in specimens that had been obtained by ultrasound ( US)-guided fine-needle aspiration biopsy (FNAB). The immunophenotyping tech nique showed lambda light chain restriction, and PCR-based assays showed a discrete narrow band, which was diagnostic for clonal B-cell proliferation. Analyses of PCR gene rearrangement in US-guided FNAB may be a useful ancil lary technique to pathological findings for diagnosis of primary thyroid ly mphoma, especially for differentiation between low-grade B-cell lymphomas a nd Hashimoto's thyroiditis.