Is a five-category reporting scheme for thyroid fine needle aspiration cytology accurate? Experience of over 18,000 FNAs reported at the same institution during 1998-2007.
OBJECTIVE
Fine needle aspiration (FNA) has long been recognized as an essential technique for the evaluation of thyroid nodules. Although specific cytological patterns have been recognized, a wide variety of reporting schemes for thyroid FNA results have been adopted. This study reports our experience with a five-category reporting scheme developed in-house based on a numeric score and applied to a large series of consecutive thyroid FNAs. It focuses mainly on the accuracy of thyroid FNA as a preoperative test in a large subset of histologically distinct thyroid lesions.


METHODS
During the 1998-2007 period, 18,359 thyroid ultrasound-guided FNAs were performed on 15,269 patients; FNA reports were classified according to a C1-C5 reporting scheme: non-diagnostic (C1), benign (C2), indeterminate (C3), suspicious (C4), and malignant (C5).


RESULTS
Non-diagnostic (C1) and indeterminate (C3) FNA results totalled 2,230 (12.1%) and 1,461 (7.9%), respectively, while suspicious (C4) and malignant (C5) results totalled 238 (1.3%) and 531 (2.9%), respectively. Histological results were available in 2,047 patients, with thyroid malignancy detected in 840. Positive predictive value of FNA was 98.1% with a 49.0 likelihood ratio (LR) of malignancy in patients with a C4/C5 FNA report.


CONCLUSIONS
This five-category scheme for thyroid FNA is accurate in discriminating between the virtual certainty of malignancy associated with C5, a high rate (92%) of malignancy associated with C4, and a 98% probability of a histological benign diagnosis associated with C2. Further sub-classifications of C3 may improve the accuracy of the diagnostic scheme and may help in recognizing patients eligible for a 'wait and see' management.
Piana
S
S
Department of Pathology, Arcispedale Santa Maria Nuova, Reggio Emilia, Italy. Simonetta.piana@asmn.re.it
Frasoldati
A
A
Ferrari
M
M
Valcavi
R
R
Froio
E
E
Barbieri
V
V
Pedroni
C
C
Gardini
G
G
D044963:Biopsy, Fine-Needle; D006801:Humans; D009367:Neoplasm Staging; D058028:Research Report; D013961:Thyroid Gland / Q000473:pathology*; D013964:Thyroid Neoplasms / Q000473:pathology