GENE REARRANGEMENT OF IMMUNOGLOBULIN AS A MARKER OF THYROID LYMPHOMA

Thyroid lymphoma occurs most commonly in the thyroid gland in associat ion with Hashimoto's thyroiditis. Histologic findings occasionally can not distinguish lymphoma from Hashimoto's thyroiditis, which creates a serious problem of whether treatment should be initiated. For this st udy, we examined 33 lymphoma tissues and 10 thyroid tissues from patie nts,vith Hashimoto's thyroiditis for the presence of gene rearrangemen t of immunoglobulin, which represents clonality of B-cell-derived tumo rs. Genomic DNA from thyroid tissues was digested with Bam H1 and Hind III restriction enzymes followed by electrophoresis. A Southern blot was performed with an IgH-JH probe or IgL-J kappa probe to detect gene rearrangement. Of the 33 lymphoma tissues, 27 (85%) showed gene rearr angement of immunoglobulin, whereas none of Hashimoto's thyroiditis ti ssue showed gene rearrangement. Five patients with a positive histolog ic diagnosis of lymphoma showed a negative gene rearrangement and were treated as having lymphoma. We encountered one case of lymphoma (plas macytoma) in which gene rearrangement (not histologic findings) was di agnostic. Gene rearrangement of immunoglobulin can be used to detect t hyroid lymphoma, particularly when the histologic diagnosis is inconcl usive. The sensitivity of detecting thyroid lymphoma by the Southern b lot method was about 85% in the present series.