Diagnosis of thyroid malignant lymphoma by reverse transcription-polymerase chain reaction detecting the monoclonality of immunoglobulin heavy chain messenger ribonucleic acid

Distinguishing between thyroid malignant lymphoma and lymphocytic thyroidit is (Hashimoto's thyroiditis) is quite difficult and problematic. Molecular techniques to detect clonal lymphoid proliferation based on Ig heavy chain (IgH) gene rearrangement may be used to facilitate more accurate diagnosis of malignant lymphoma. We recently established a method for diagnosing thyr oid tumors by analyzing ribonucleic acids (RNAs) extracted from the needles used for fine needle aspiration biopsy (aspiration biopsy-RT-PCR). By appl ying the aspiration biopsy-RT-PCR method to detection of the monoclonality of IgH messenger RNA (mRNA), an accurate molecular-based diagnosis of malig nant lymphoma can be established as an adjunct to cytological diagnosis. We first studied RNAs from fresh tissues samples of 8 cases of Hashimoto's th yroiditis and 18 malignant lymphomas to detect the monoclonality of IgH mRN A by seminested RT-PCR. Monoclonality was detected in 8 of 18 (44.4%) malig nant lymphomas, but in none of the 8 cases of Hashimoto's thyroiditis. We t hen studied aspirates from 10 cases of thyroid malignant lymphoma, 4 cases of Hashimoto's thyroiditis, and I case each of adenomatous goiter and papil lary carcinoma. Monoclonality was detected in the aspirates from 4 of 10 ma lignant lymphomas (40%), but not from other tissues. Thus, RT-PCR detection of monoclonality of IgH mRNA in addition to cytological examination may be useful in diagnosing thyroid malignant lymphoma.