TEST:

VENTANA pan-TRK (EPR17341) Assay

Our findings suggest that immunohistochemistry can be used as a screening test, but requires molecular confirmation. Our finding of NTRK3 fusion in squamous cell carcinomas with limited treatment options, suggests that the driver function of this gene may be more effective in this group.

Our work showed a high false positive rate in mesenchymal neoplasms using clone EPR17341. Clone A7H6R demonstrated a higher specificity and therefore could be considered in clinical practice for screening mesenchymal tumors for NTRK1 - 3-rearrangements, eventually leading to less unnecessary reflex testing.

A total of 15 SCB tumors from 9 patients were analyzed, with 4 patients providing paired primary and relapsed tumor samples. The median age at diagnosis was 64 years (range 45-78). Median tumor size was 1.7 cm (range 0.6-9.5 cm).

P=N/A; Trial completion date: Mar 2024 --> Mar 2025

In our experience, the comprehensive screening approach based on morphological and clinical/ molecular inclusion criteria, along with the use of immunohistochemical techniques (pan-TRK antibody), significantly enhances the detection rate of NTRK fusions (5. 8% vs. 0.

Pan-TRK IHC shows some utility as a diagnostic and surrogate marker for NTRK screening however, physiologic or non-specific expression may lead to false-positive results.

No NTRK or ALK translocations or increased copy number/amplification were identified in all eight cases which had fluorescence in situ hybridisation and/or next generation sequencing for NTRK1-3 and ALK available for assessment. None of the cases expressed BRAF-V600E.Although our study is limited, our report is the first to document PanTRK expression in AFH in the absence of identifiable NTRK1-3 gene alterations.

Even though pan-TRK immunohistochemical expression is not entirely sensitive or specific for NTRK-rearranged sarcomas, these neoplasms tend to exhibit diffuse staining of moderate/strong intensity, unlike its mimics. Pan-TRK should be performed in monomorphic uterine (corpus and cervix) spindle cell neoplasms that are negative for smooth muscle markers and hormone receptors and positive for CD34 and/ or S100. Ultimately, the diagnosis requires molecular confirmation.

CANTRK illustrates a successful strategy to accelerate the multicenter harmonization and implementation of pan-TRK immunohistochemical screening that achieves high diagnostic sensitivity by using laboratory-developed tests where laboratories used centrally developed reference materials. The measurement of analytic sensitivity by using TRK calibrators provided additional insights into IHC protocol performance.

Conclusion This study supports the known conclusion that the diagnosis of a NTRK-related fusion-driven neoplasm cannot be made based solely on the immunohistochemical expression of panTRK. The significance of panTRK immunohistochemical expression in multiple different uterine mesenchymal neoplasms without NTRK-related fusions is, as of yet, not entirely clear but continues to raise questions regarding a) the exact mechanisms causing this, and b) the possible therapeutic utility of selective TRK inhibitors in the treatment of these neoplasms.

After reviewing the literature, possible NTRK fusions justified by their spindle-shaped morphology have not been studied. We carried out this study not for diagnostic purposes but to analyze possible new molecular associations and treatment targets.

Pan-TRK should be performed in uterine monomorphic spindle neoplasms negative for smooth muscle markers and hormone receptors and variably positive for CD34 and S100. The diagnosis of an NTRK-rearranged sarcoma requires molecular confirmation but pan-TRK immunohistochemistry is a useful screening tool to direct which cases require molecular testing