From Smear to Sequence: Using Thyroid Cytology Smear Slides for ThyroSeq Molecular Analysis and Clinicopathologic Insights From 61 Tested Nodules.

Context.—: In the absence of conventional testing media, thyroid cytology smear slides may be used for molecular analysis of nodules with indeterminate cytology results.

Objective.—: To present solutions for overcoming challenges of ThyroSeq testing using smear slides and report findings from tested nodules.

Design.—: We developed software to parse unstructured ThyroSeq reports for actionable data extraction. To ensure compliance with sample retention requirements, substitute specimen records were created by digitizing smear slides before they were exhausted for molecular analysis. We streamlined the test send-out process and recorded the clinical, molecular, and pathologic findings of the cases in our cohort.

Results.—: We submitted 61 thyroid fine-needle aspiration specimens from 59 cases for ThyroSeq testing. All 61 specimens were adequate for DNA analysis, and only 1 was insufficient for RNA analysis. In 8 cases, the smear slide was the only viable sample for molecular testing. A total of 21 specimens (34.4%) had a positive ThyroSeq result. Gene mutations were the most common findings, with 16 mutations detected in 13 "positive" specimens. Additionally, copy number alterations, gene expression alterations, and gene fusions were identified.

Conclusions.—: This study presents our approach to extending the utility of thyroid cytology smear slides by enabling molecular analysis, particularly when routine sample types are unavailable. High adequacy rates and successful detection of molecular alterations highlight the potential of smear slides in molecular testing, reducing the need for repeated procedures and streamlining care. Effective communication between clinical and cytology teams remains essential to manage the additional workload.