INDETERMINATE FINE-NEEDLE ASPIRATION BIOPSY OF THE THYROID - IDENTIFICATION OF SUBGROUPS AT HIGH-RISK FOR INVASIVE-CARCINOMA

Background. We examined the various cytologic features of indeterminat e thyroid fine-needle aspirates along with known clinical and radiolog ic risk factors to determine whether any parameters were predictive of malignancy. Methods. Indeterminate fine-needle aspirates were prospec tively categorized into four subgroups; (1) suspicious for papillary c arcinoma, (2) follicular neoplasm, (3) Hurthle cell neoplasm, and (4) hypercellular follicular aspirates with colloid. Several clinical risk factors were examined, and subgroup comparisons were performed with F isher's exact test. Results. Of 571 fine-needle aspirate cytologic fin dings 104 were interpreted as indeterminate for malignancy, and 81 pat ients underwent thyroidectomy. Invasive cancer was diagnosed in 9 to 1 0 lesions cytologically suspicious for papillary carcinoma, 8 of 43 fo llicular neoplasms, 5 of 18 Hurthle cell neoplasms, and 0 of 10 hyperc ellular aspirates. Cytologic subgroup (p < 0.0001) and age of 50 years or older (p = 0.008) were the only significant predictors of malignan cy. When used together, age of so years or older and a cytologic diagn osis of follicular or Hurthle cell neoplasm also identified a subgroup of patients at high risk (9 of 20) of invasive malignancy. Conclusion s. The majority of invasive cancers (18 of 22, 82%) were found in pati ents whose lesions were suspicious for papillary carcinoma or in patie nts 50 years or older with follicular or Hurthle cell neoplasms. The r isk of carcinoma in these combined subgroups (18 of 30, 60%) warrants early surgical intervention.