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.