Recurrent schwannomatosis with mosaic SMARCB1 loss: A case report

Schwannomatosis is a non-cancerous disorder causing peripheral nerve sheath tumors (schwannomas), often leading to chronic pain. It is linked to loss of SWI/SNF related, matrix associated, actin dependent regulator of chromatin subfamily B member 1 (<i>SMARCB1)</i> or leucine zipper-transcription regulator 1 <i>(LTZR1)</i> gene function, though some patients may initially show minor mutations or no clinical signs, resulting in misdiagnosis, missed assessments, increased recurrence risk, unawareness of malignancy and overlooked genetic counseling during pregnancy. The present study reports a patient with a sporadic synonymous mutation in the <i>SMARCB1</i> gene [SNP <i>c.1032 C>T (p.Gly344Gly {GGC>GGT})</i> in exon 8]. This patient, a 53-year-old female with an 8-year history of schwannomatosis, presented to the neurosurgical department for recurrent tumor removal. Tumor tissue was analyzed using immunohistochemistry, hematoxylin and eosin staining, and enzyme-linked immunosorbent assay. Initially, the clinical impact of the <i>SMARCB1</i> mutation on schwannomatosis was unclear. However, resected schwannomas showed 10-60% mosaic loss of nuclear <i>SMARCB1</i> protein, with protein assays confirming low <i>SMARCB1</i> levels, particularly in the distal thigh schwannoma. This case highlights the tumorigenic potential of <i>SMARCB1</i> single nucleotide polymorphisms, emphasizing the need for multimodal diagnosis, long-term follow-up, awareness of recurrence and malignancy, and timely surgical planning in schwannomatosis patients.