FNAC and frozen section correlations with definitive histology in thyroid diseases

Nithiananthan Mayooran, Peadar S. Waters, Tahir Y. Kaim Khani, Michael J. Kerin, Denis Quill

The ability to diagnose thyroid cancers pre-op or intra-operatively by fine needle aspiration cytology (FNAC) or frozen section (FS) leads to the delivery of appropriate one-stage surgical management. We aim to study the concordance and discordance of FNAC and FS with final histology in thyroid pathologies. All thyroid procedures from 2007 to 2011(n = 423), involving FNAC and or frozen section in their management pathway were included. FNAC (n = 159) were classified in a five-tier system (Nondiagnostic, Benign, Atypical, Suspicious or Malignant). FS (n = 128) were classified as inconclusive, benign, suspicious or malignant. FNAC and FS were correlated with final histopathology. 159 out of 423 patients had FNAC (PPV 85.1 %), 26 inadequate specimens noted, benign cytology 57, atypical (n = 23), follicular neoplasm (n = 27), suspicious for malignancy (n = 16) and malignant 11. 13 out of 27 follicular neoplasm and 6 of atypical FNAC cases showed malignancy in their final histopathology. Frozen sections; total of 126 patients had intra-operative frozen section biopsies performed. Overall 105 out of 126 FS biopsies were benign; 21 malignancies detected intraoperatively. Three FS were inconclusive and reported benign in final histopathology. Overall, FNAC demonstrated a PPV of 66.6 % and NPV of 84.6 %. FS demonstrated PPV and NPV of 76.1 and 85.7%, respectively. In conclusion, FNAC is considered as the best modality to triage the thyroid nodule pre-operatively. Atypical and follicular neoplasm cytology categories warrant further clinical assessment and close follow-ups when appear benign. The intra-operative frozen sections are helpful to perform a one-stage operation for suspicious thyroid lesion. This study also highlights the recognised limitation of intra-operative frozen section analysis of thyroid neoplasia.