Limited Accuracy of Pan-Trk Immunohistochemistry Screening for NTRK Rearrangements in Follicular-Derived Thyroid Carcinoma

Paving the path toward multi-omics approaches in the diagnostic challenges faced in thyroid pathology

INTRODUCTION

Despite advancements in diagnostic methods, the classification of indeterminate thyroid nodules still poses diagnostic challenges not only in pre-surgical evaluation but even after histological evaluation of surgical specimens. Proteomics, aided by mass spectrometry and integrated with artificial intelligence and machine learning algorithms, shows great promise in identifying diagnostic markers for thyroid lesions.

AREAS COVERED

This review provides in-depth exploration of how proteomics has contributed to the understanding of thyroid pathology. It discusses the technical advancements related to immunohistochemistry, genetic and proteomic techniques, such as mass spectrometry, which have greatly improved sensitivity and spatial resolution up to single-cell level. These improvements allowed the identification of specific protein signatures associated with different types of thyroid lesions.

EXPERT COMMENTARY

Among all the proteomics approaches, spatial proteomics stands out due to its unique ability to capture the spatial context of proteins in both cytological and tissue thyroid samples. The integration of multi-layers of molecular information combining spatial proteomics, genomics, immunohistochemistry or metabolomics and the implementation of artificial intelligence and machine learning approaches, represent hugely promising steps forward toward the possibility to uncover intricate relationships and interactions among various molecular components, providing a complete picture of the biological landscape whilst fostering thyroid nodule diagnosis.

High-Grade Non-Anaplastic Thyroid Carcinomas of Follicular Cell Origin: A Review of Poorly Differentiated and High-Grade Differentiated Carcinomas

Poorly differentiated thyroid carcinoma (PDTC) and high-grade differentiated thyroid carcinoma (HGDTC) are considered high-grade follicular-derived thyroid carcinomas, with prognoses intermediate between well-differentiated and anaplastic thyroid carcinoma. Both share the presence of invasion, thyroid follicular-cell origin, and tumor necrosis or increased mitoses (≥ 3 mitoses per 2 mm² in PDTC and ≥ 5 mitoses per 2 mm² in HGDTC), without anaplastic dedifferentiation. PDTC must possess solid, trabecular, or insular growth and lack classic papillary-like nuclei; HGDTC can be of any architectural or nuclear morphology (follicular-like, papillary-like, oncocytic). Transformation may be accompanied by acquisition of high-risk mutations (such as TP53 or TERT promoter) on top of RAS-like or BRAF p.V600E-like (including NTRK-fusion) initial driver mutations. These carcinomas most frequently affect adults and often present with metastases (20-50%) or wide local invasion. As PDTC and HGDTC may be radioactive iodine resistant, post-surgical therapy may consist of external beam radiotherapy or targeted, mutation-dependent chemotherapy, such as tyrosine kinase inhibitors. Ten-year disease specific survival is as low as 50%. Awareness of high-grade features in the diagnostic setting is important for patient prognosis and triage of tissue for molecular analysis in order to guide relevant clinical management and therapy.

A systematic comparison of pan-Trk immunohistochemistry assays among multiple cancer types

AIMS

NTRK rearranged tumours are rare but can be successfully treated using anti-TRK-targeted therapies, making NTRK testing important for treatment choices in patients with advanced cancers. Pan-Trk immunohistochemistry (IHC) has become a valuable and affordable screening tool in many laboratories. Unfortunately, the choice of antibodies and IHC protocols to investigate biomarkers is not standardised. In this study, we compared the performance of four pan-Trk IHC methods, using three different clones, primarily in NTRK fusion-positive tumours.

METHODS AND RESULTS

We studied the performance of four pan-Trk IHC methods using three different clones: EPR17341 (Abcam and Ventana), EP1058Y (Abcam) and A7H6R (Cell Signaling) in 22 molecularly confirmed NTRK rearranged tumours. Additionally, selected NTRK fusion-negative tumours were further included: NTRK mutated (n = 8) and amplified (n = 15) tumours as well as NTRK fusion-negative tumours driven by other gene fusions, such as ALK, ROS1 and BCOR (n = 20), as well as salivary gland tumours (n = 16). Inter-rater agreement of three pathologists was additionally calculated, including H-score. With clone EPR17341 (Abcam in-house and ready-to-use Ventana protocol), all molecularly confirmed NTRK1-3 rearranged tumours were positively detected by immunohistochemistry, while the other clones missed NTRK2-3 rearranged tumours. For the fusion-negative cohort we found the best performance (least false-positive cases) using the clone A7H6R (Cell Signalling).

CONCLUSION

Given the therapeutic importance, testing for NTRK rearrangements in daily practice has become necessary and, despite IHC being a fast and affordable tool, using it in routine diagnostics is complicated and requires a high level of expertise.