Establishment of aspiration biopsy RNA diagnosis of malignant lymphoma

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Distinguishing between thyroid malignant lymphoma and lymphocytic thyroiditis (Hashimoto's tbyroiditis) is 'quite difficult and problematic. Molecular techniques to detect clonal lymphoid proliferation based on immunoglobulin heavy chain (IgH) gene rearrangement may be used to facilitate more accurate diagnosis of malignant lymphoma. We tried to establish a method for diagnosing thyroid tumors by analyzing nucleic acids extracted from the needles used for fine needle aspiration biopsy. We first studied RNAs from fresh tissues samples of 8 cases of Hashimoto's thyroiditis and 18 malignant lyrnphomas to detect the monoclonality of IgH mRNA by semi-nested R.T-PCR. Monoclonality was detected in 8 of 18 (44.4%) malignant ryrnphomas but none of the 8 cases of Hashimoto's thyroiditis. We then studied aspirates from 10 cases of thyroid malignant lymphoma, 4 cases of Hashimoto's thyroiditis, and one case each of adenomatous goiter and papillary carcinoma. Monoclonality was detected in the aspirates from 4 of 10 malignant lymphomas (40%) but not from other tissues. Thus RT-PCR detection of monoclonality of IgH mRNA in addition to eytological examination may be useful in diagnosing thyroid malignant lyraphoma. In order to increase the sensitivity of this method, we examine the usefulness of degenerated oligonucleotide primed (OOP) PCR to amplify the extracted DNAs in fine needle aspiration biopsies. By mixing a primer specific for the JH sequence, DOP-PCR could produce 3-10kbp PCR product, which could be used in linker-ligation PCR or Southern blot analysis. These results may lead us to establish a low-invasive diagnostic method of malignant lymphoma in the future study by utilizing DNAs instead of RNAs obtained by fine needle aspiration biopsy