Amyloid light-chain deposition in a schwannoma

Systemic amyloid light-chain amyloidosis is a protein misfolding disorder characterized by extracellular deposition of amyloid fibrils derived from abnormal clonal immunoglobulin light chains in various organ systems. While amyloid light-chain amyloidosis is known to cause neuropathy when it involves the peripheral nervous system, deposition within peripheral nerve sheath tumors has not been previously reported. A 68-year-old man with a history of systemic amyloid light-chain amyloidosis with cardiac and renal involvement presented with a painful mass in the lower third of the leg. Imaging was consistent with a peripheral nerve sheath tumor. Pathologic evaluation demonstrated a schwannoma, which unusually contained prominent amyloid deposition, subsequently demonstrated to be of amyloid light-chain-type by mass spectrometry-based proteomic analysis. Amyloid light-chain deposition has been characterized in different organs and tissues, including neurosurgical specimens such as peripheral nerve. This case highlights a new finding of amyloid light-chain deposition in a schwannoma, which likely resulted from gradual amyloid light-chain deposition in a slow-growing schwannoma prior to treatment of systemic amyloid light-chain amyloidosis. Treatment protocols vary dramatically. Therefore, it is crucial to establish the correct amyloid type as well as to distinguish localized from systemic disease.

Duke Scholars

Author Brandon Wayne Smith Neurosurgery