When fine-needle aspiration biopsy cannot exclude papillary thyroid cancer: a therapeutic dilemma.

HYPOTHESIS Clinical or cytologic factors predictive of malignancy can be identified and incorporated into a treatment algorithm for patients with a fine-needle aspiration biopsy (FNAB) specimen interpreted as "suspicious for" papillary thyroid cancer (PTC). DESIGN Retrospective review of a prospectively maintained database. SETTING University-affiliated tertiary care hospital. PATIENTS Seven hundred thirty-eight patients with nodular thyroid disease evaluated between 1990 and 2004. INTERVENTIONS Patients with an FNAB specimen suspicious for PTC were identified. The frequency of carcinoma was determined. Clinical features were reviewed. The FNAB specimens suspicious for PTC were examined in a blinded fashion to determine if specific cytologic features were important in distinguishing benign vs malignant disease. MAIN OUTCOME MEASURES The presence of specific clinical and cytologic features was correlated with the incidence of carcinoma. A secondary outcome measure was to determine the value of frozen section examination in establishing the extent of thyroidectomy. RESULTS Forty-five patients (7%) had an FNAB specimen suspicious for PTC; 18 (40%) of these patients had carcinoma. Prominent nuclear inclusions and/or grooves, papillary formations, and the absence of colloid were features associated with PTC (P<.05). No clinical features reliably identified malignant disease. Frozen section examination results altered treatment in 15 (56%) of 27 patients. CONCLUSIONS An FNAB specimen suspicious for PTC is associated with a 40% incidence of carcinoma. Extensive nuclear inclusions and/or grooves, papillary formations, and the absence of colloid are predictive of carcinoma. Rare intranuclear inclusions and/or grooves alone in an otherwise benign-appearing specimen are uniformly associated with benign disease. Frozen section examination is of value in determining the extent of thyroidectomy.