OBJECTIVETo study the immunoglobulin gene rearrangement patterns in Hashimoto's thyroiditis (HT) and primary thyroid lymphoma (PTL), and to analyze the relationship between the two diseases.

METHODSFormalin-fixed and paraffin-embedded tissues of 11 cases of PTL and 38 cases of HT as well as their clinical data, were retrieved. The latter group was further subcategorized into classic HT and suspicious PTL. Gene rearrangement studies for immunoglobulin heavy chains and light chains were carried out by polymerase chain reaction (PCR) using VH, FR3A and FR3kappa primers.

RESULTSThere was an increasing trend in immunoglobulin gene rearrangement rate for classic HT (10.7%), suspicious PTL (40.0%) and PTL (72.7%) groups. In general, a female predilection was observed. This sex predilection however was less obvious in the PTL group. There was no relationship between serum antibody (both thyroglobulin and thyroid peroxidase) titers and gene rearrangement patterns.

CONCLUSIONSHT and PTL show morphologic overlaps and may not be clearly distinguished on the basis of light microscopy alone. PCR-based immunoglobulin gene rearrangement study may be helpful in the detection of cases with early lymphomatous transformation of HT.