Malignant Potential of Temporal Bone Paragangliomas With Reference to <scp>GAPP</scp> System

ABSTRACT Objectives To evaluate the temporal bone paragangliomas (so‐called glomus tumors, TB‐PGLs) via the Grading System for Adrenal Pheochromocytoma and Paraganglioma (GAPP) and succinate dehydrogenase subunit B (SDHB) immunohistochemistry, and to discuss their implications for postoperative follow‐up and treatment strategies. Methods This report is a retrospective descriptive case series of histopathological findings from surgically resected TB‐PGL tissues. A retrospective analysis of 10 cases of TB‐PGL that required otologic surgical intervention at our institution between 2016 and 2025 was conducted. Tumors were classified using the Fisch and Glasscock–Jackson systems. Histopathological characteristics were assessed via GAPP scoring and SDHB immunostaining (primary outcome). The surgical approach, extent of resection, postoperative complications, and hearing preservation outcomes were also reviewed (second outcome). Results Nine of 10 tumors were classified as moderately differentiated based on the GAPP. SDHB loss was observed in larger tumors (Classes C1 and C2). Complete resection was achieved in 7/10 cases without major cranial nerve deficits. Hearing preservation surgery was performed in seven cases, whereas hearing was sacrificed in three cases owing to tympanic membrane lateralization. Conclusion Most of the TB‐PGLs were classified as moderately differentiated based on the GAPP and SDHB deficiency was observed in two cases. These findings suggest that long‐term follow‐up may be indicated for patients with TB‐PGLs. Postoperative follow‐up should incorporate pathological assessments, and adjuvant therapy may be considered in selected cases. Larger, multicenter studies with long‐term follow‐up are needed to correlate the long‐term malignant potential of TB‐PGLs to GAPP scoring. Level of Evidence 4