Has Afirma gene expression classifier testing refined the indeterminate thyroid category in cytology?

Area of Science:

• Endocrinology
• Surgical Pathology
• Molecular Diagnostics

Background:

• Thyroid fine-needle aspiration (FNA) is crucial for evaluating thyroid nodules.
• Indeterminate FNA results occur in up to 30% of cases, often leading to unnecessary surgeries.
• The gene expression classifier (GEC) test offers molecular analysis for indeterminate thyroid cytology.

Purpose of the Study:

• To evaluate the impact of the gene expression classifier (GEC) test in refining diagnoses of indeterminate thyroid nodules within a single institution.
• To assess changes in surgical intervention rates and malignancy detection after GEC implementation.

Main Methods:

• Retrospective analysis of thyroid FNAs over a 20-month period post-GEC implementation.
• Selection of indeterminate cytology cases with GEC testing, categorized into subgroups.
• Comparison of surgical follow-up data and malignancy rates with pre-GEC data.

Main Results:

• Of 189 indeterminate cases, 42% were classified as benign and 50% as suspicious by GEC.
• The excisional rate for atypia/follicular lesion of undetermined significance decreased from 63% to 35% post-GEC.
• Malignancy rates in excised thyroids increased from 35% to 47% post-GEC.

Conclusions:

• The gene expression classifier (GEC) test effectively reclassifies indeterminate thyroid cytology, identifying 42% as benign.
• GEC testing significantly reduces the rate of unnecessary thyroid surgeries.
• The GEC test improves the diagnostic yield of surgical interventions for thyroid nodules.