PROTON MAGNETIC-RESONANCE AND HUMAN THYROID NEOPLASIA .1. DISCRIMINATION BETWEEN BENIGN AND MALIGNANT NEOPLASMS

Purpose: Thyroid nodules are very common, yet the vast majority are bi ologically benign. The extreme difficulty facing the clinician selecti ng potentially malignant thyroid nodules for surgery was the subject o f a recent editorial by Ernest L. Mazzaferri in the American Journal o f Medicine (93:359-362, 1992). Here we evaluate the potential of proto n magnetic resonance Spectroscopy (H-1 MRS) to provide a solution to t his problem. Patients: Thyroid tissue from fifty-three patients underg oing partial or total thyroidectomy for solitary thyroid nodules were assessed by H-1 MRS. Results: When compared with the histologic diagno sis, H-1 MRS distinguished normal thyroid tissue (n = 8) from invasive papillary (n = 9), anaplastic (n = 1), and medullary (n = 1) carcinom as with P values of < 0.0001, based on altered cellular chemistry. The same magnetic resonance (MR) criteria categorized pathologically prov en follicular carcinoma (n = 8) (established as such by the presence o f capsular or vascular invasion at the periphery of the tumor, or by t he presence of metastases in the patient) with the other thyroid cance rs (P <0.0001). All other ''benign'' follicular neoplasms (n = 34), in cluding five atypical follicular adenomas, were assessed by the same 1 H MRS criteria and found to fit into one of the two above categories, viz. analogous fo benign or malignant thyroid tissue. Conclusions: Pro ton MRS has the potential to separate out a group of truly benign foll icular neoplasms from follicular tumors (both follicular adenomas and follicular carcinomas) that have an atypical follicular pattern on cyt ologic examination. This is the first report of an objective diagnosti c procedure that has the potential to obviate surgical excision in a s ignificant number of patients with benign follicular adenomas, indepen dent of exhaustive histopathologic assessment.