DIAGNOSIS OF FOLLICULAR THYROID LEGIONS BY PROTON MAGNETIC-RESONANCE ON FINE-NEEDLE BIOPSY

Most thyroidectomies are currently performed for diagnostic purposes. It has been established that proton magnetic resonance spectroscopy (M RS) on excised thyroid tissue can distinguish normal thyroid from inva sive carcinomas (P < 0.0001). The purpose of this study was to assess whether the same discrimination could be obtained preoperatively from fine needle biopsy (FNB). This has clinical importance because cytolog ical examination of fine needle aspirates cannot distinguish between b enign and malignant follicular thyroid lesions. Here we demonstrate a sensitivity of 95% for proton MRS to correctly identify clinically or histologically proven carcinoma. MRS measurements were made on FNB spe cimens (containing as few as 10(6) cells) from solitary thyroid nodule s. MR assessment of FNB was inconsistent with that of the correspondin g tissue in only 6.5% of cases. The discrimination between cancer and normal tissue was based on altered cellular chemistry measured as a on e-dimensional spectral ratio of resonances from the amino acid lysine and lipid. Benign follicular lesions were separated into two groups: 6 7% with a spectral ratio similar to malignant thyroid tumors, and 33% with a spectral ratio comparable to that in normal thyroid tissue. Thu s, in contrast with histopathology, MRS offers a method for assessment of FNB of follicular lesions with the potential to identify a biologi cally benign group, which could avoid thyroid surgery for purely diagn ostic purposes.