[375] Retrospective Review of False-Negative Thyroid FNAs

Jerome Jean-Gilles, Christopher L Owens, Andrew Fischer. UMASS Memorial Medical Center, Worcester, MA

Background: Fine needle aspiration (FNA) cytology is a cost-effective procedure that provides specific diagnoses rapidly with minimal complications. A major utility of FNA is to prevent unnecessary surgery in patients whose findings are unequivocally benign. False negative diagnoses are reported at varying frequencies in the literature. The purpose of this study was to systematically analyze false negative thyroid FNAs (FN-TFNA) and determine the impact patient outcome.
Design: Medical records of 316 consecutive patients over a four-year period (2007-2011) were reviewed to identify cases in which a prior FNA was diagnosed as "negative for malignancy" in the same nodule that had a subsequent malignant surgical pathology diagnosis. Two experienced cytopathologists re-adjudicated the FNAs to determine whether a diagnostic interpretative error occurred. For a subset of cases with sampling error, re-review of the surgical specimen was performed. Various clinical parameters and pathologic data were recorded and analyzed.
Results: Nine malignant nodules in 8 patients with FN-TFNA were identified. The nine malignant nodules include 6 follicular variants of papillary thyroid carcinoma and 3 follicular carcinomas. The tumors were organ confined in seven of eight patients. Only one of eight patients had lymph node involvement at the time of thyroidectomy. Seven of eight patients are alive and free of disease on follow-up studies (avg. follow-up 25 months). One of eight patients is alive with radiographic evidence of metastatic disease. The average time from the FN-TFNA to diagnosis was 11.2 months (2-29 months). Adjudicated diagnoses agreed with the negative FNA diagnosis in five of nine cases. In the other four cases, two were adjudicated to be atypical and two were adjudicated to be suspicious for carcinoma.
Conclusions: FN-TFNAs occur in nodules harboring low-grade tumors and the majority of the time are low stage at diagnosis. The delay in diagnoses did not directly lead to adverse clinical outcomes in our series, as the only patient with metastatic disease was promptly diagnosed due to the clinical behavior or the tumor. FN-TFNAs encompass both interpretive and non-interpretive errors. Non-interpretive errors are thought to be due to sampling error, tumor heterogeneity or terminal differentiation of tumor cells. Review of FN-TFNA due to interpretative error can be a valuable educational tool. Although FN-TFNA is not desired, clinical outcomes in our series suggest that thresholds should not be lowered to the point of over interpreting mildly atypical aspirates.
Category: Cytopathology

Wednesday, March 21, 2012 1:00 PM

Poster Session VI # 60, Wednesday Afternoon


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