Analysis of inconclusive fine-needle aspiration of thyroid follicular lesions

Abstract

To evaluate all inconclusive fine-needle aspiration biopsy (FNAB) specimens from thyroid follicular lesions with subsequent histologic diagnosis at St John Hospital and Medical Center, Detroit, MI. The criterion for specimen adequacy used in our institution was also reexamined to determine whether it was too stringent. We reviewed 45 inconclusive FNAB samples. Only cases that underwent surgical intervention were considered. Specimen adequacy was determined by the presence of at least 8-10 tissue fragments of well-preserved follicular epithelium on at least two slides; each tissue fragment should have a minimum of 8-10 cells. Different cytologic characteristics-cellularity, cellular architecture, nuclear pleomorphism, inclusion/grooves, chromatin, Hürthle cell change, lymphocytes, macrophages, colloid, and multinucleated giant cells-were scored and compared with final surgical diagnosis. The surgical procedure performed was also analyzed. Review of these 45 surgical specimens found 28 (62.2%) multinodular goiters, 14 (31.1%) nodular hyperplasias, 2 (4.4%) follicular adenomas, and one (2.2%) with invasive follicular carcinoma. Forty-three (95.6%) of these cases were female and 2 (4.4%) were male. Cytologic review showed 2 acellular samples, 10 cases containing macrophages only, 10 aspirates with macrophages and an inadequate number of follicular cells, and 23 specimens with an inadequate number of follicular cells. Twenty-three patients underwent total thyroidectomy; 20, lobectomy; and 2, isthumusectomy. Almost 98% of the patients with inconclusive FNAB had benign lesions. This finding encouraged us to continue using our criteria for adequacy because of the importance of a negative report. Patients in our series, who underwent thyroidectomy after an inconclusive or nondiagnostic aspirate, had a malignancy rate of 2.2%, which was no worse than patients with a benign preoperative diagnosis. A balanced approach with careful follow-up for nondiagnostic cytology is prudent.