Exp Clin Endocrinol Diabetes 2014; 122 - P144
DOI: 10.1055/s-0034-1372161

Molecular analysis of residual ThinPrep material increases sensitivity and allows molecular diagnostics for non-diagnostic samples

M Eszlinger 1, J Krane 2, E Cibas 2, R Paschke 1
  • 1Universität Leipzig, Klinik für Endokrinologie und Nephrologie, Leipzig, Germany
  • 2Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, United States

Molecular testing of routinely available thyroid nodule fine needle aspiration (FNA) material has many advantages. Recently, we described the molecular testing of air-dried smears. Now, we performed molecular testing on liquid based FNA material and analyzed the remaining CytoLyt-FNA material for BRAF, RAS, RET/PTC and PAX8/PPARG mutations.

Thyroid FNAs were classified according to the Bethesda System for Reporting Thyroid Cytopathology after routine cytological examination. The remaining material from all available cases was used for blinded analysis of BRAF, NRAS, HRAS, KRAS point mutations and RET/PTC and PAX8/PPARG rearrangements by high resolution melting PCR/pyrosequencing, and qPCR, respectively.

A total of 597 consecutive cases were collected and stored at 8 °C for up to 6 months. Molecular analysis was possible for 391 cases. Higher volumes of remaining material (> 2 ml) were associated with higher diagnostic success rates (23% vs. 79%, p < 0.001, chi-squared test). Mutations and rearrangements were detected in 11.5% of atypias of undetermined significance, 33% suspicious cases, 47.1% malignant cases, 7.1% follicular neoplasms, 9.3% benign cases, and 2.5% non-diagnostic (molecular analysis possible for 63.2%) samples. Compared to histology (available for 211 samples), cytology and molecular analysis increased sensitivity, specificity, PPV, and NPV compared to cytology alone to 86.7%, 98.1%, 98.7%, and 81.5%, respectively, considering 13 mutation-positive but histologically benign cases as true positives.

Mutational analysis is feasible on residual ThinPrep material and has the advantage of not requiring additional FNA procedures or dedicated passes, special preservation, or storage. Its reflex use can be valuable in the preoperative determination of the extent of surgery for mutation-positive cases, help to clarify 12% of AUS cases, decrease the rate of false negatives for benign cases, and allow molecular diagnostics for 63.2% of the non-diagnostic samples.