Adrenal and periadrenal schwannoma: histological, molecular and clinical characterization of an institutional case series

PURPOSE: Adrenal schwannoma (AS) and periadrenal schwannoma (PAS) are exceedingly rare Schwann cell tumors that develop from the adrenal medulla and periadrenal peripheral nerves respectively. The underlying genetic events are elusive. METHODS: We searched our institutional database for AS/PAS cases and reviewed the histology and clinical outcome. Comprehensive molecular work-up was performed. RESULTS: We found reports of 4 AS/PAS cases diagnosed between 1992 and 2022 among the 1248 adrenal lesions submitted for histopathology during the same time period (0.32%). Two patients were male, two were female, and the age span was 59–80 years. Median size was 70 mm (range 50–100 mm), and from a radiology perspective, the lesions were initially suspected of malignant lesions originating from either adrenals or kidneys. Hormonal analyses were normal in all cases. Histologically, three cases were annotated as cellular AS or PAS, and one case was annotated as microcystic AS. Molecular characterization using focused next-generation sequencing did not identify SMARCB1 or NF2 mutations, alterations previously associated to schwannoma at other anatomical sites. The postoperative period was without complications for all patients, and follow-up did not show any signs of relapse or metastatic disease. CONCLUSION: AS/PAS are rare neoplasms that are most often benign, and the molecular etiology is most likely not related to mutations in established schwannoma-related genes. Since these tumors may be misinterpreted as malignant, knowledge of this entity is essential for radiologists, endocrinologists, surgeons and pathologists.