Molecular Analysis in Salivary Gland Tumors: Exploring the Diagnostic and Clinical Impact of Comprehensive Next Generation RNA Sequencing ("SalvGlandDx v2")

Abstract

PURPOSE: To evaluate the diagnostic yield and clinical impact of a comprehensive RNA-based sequencing panel ("SalvGlandDx version 2") in the work-up of salivary gland tumors. METHODS: Between 2021 and 2025, 118 salivary gland tumors were assessed by routine histological and immunohistochemical investigation, followed by SalvGlandDx v2 RNA sequencing. This panel targets the recurrent molecular alterations in salivary gland neoplasms. Pre- and post-sequencing (differential) diagnoses were compared to determine the diagnostic contribution, categorized as diagnostic confirmation (1 A), refinement (1B/2A/2B) or no impact (3). Clinical impact was scored as none (A), altered follow-up (B), radiotherapy indication (C) and/or systemic therapy (D) when comparing pre- and post-sequencing (differential) diagnoses. RESULTS: RNA sequencing was successful in 114 of 118 cases (97%). Molecular alterations were detected in 78 of 114 cases (68%), most commonly involving rearrangements of PLAG1 and HMGA2 in (carcinoma ex) pleomorphic adenoma, and MAML2 in mucoepidermoid carcinoma. Diagnostic refinement was achieved in 66 of 114 cases (58%), including 29 cases (25%) with confirmation of the pre-sequencing diagnosis and 37 cases (32%) with refinement of the pre-sequencing differential diagnosis. Clinical management was impacted in 29 of 114 patients (25%), most often affecting follow-up frequency. CONCLUSION: Comprehensive SalvGlandDx v2 RNA sequencing demonstrated high feasibility and substantial diagnostic and clinical utility in salivary gland tumors, resolving morphological and immunohistochemically ambiguous cases. In a subset of patients, use of the analysis also influenced clinical management highlighting the value of integrating RNA sequencing into routine diagnostic work-up of the varied and challenging salivary gland tumors.