LAUSR

BACKGROUND: Management of sporadic schwannomas is often dictated by a patient's clinical presentation and the tumor's behavior. For patients who are managed nonsurgically, there are little data available about the expected natural history. OBJECTIVE: To evaluate the natural history and growth patterns of extracranial schwannomas including tumors of the distal peripheral nerves, spine, and brachial plexus. METHODS: A retrospective review was performed to identify patients with nonsyndromic extracranial schwannomas at a single tertiary care institution diagnosed between 2002 and 2019. Patient data and tumor characteristics including volume were recorded. RESULTS: Two hundred twenty-seven patients were identified (mean age 51 years, 42% male, average of 27.8-month follow-up). Tumor location was distal peripheral nerve in 82, brachial plexus in 36, and paraspinal in 109. At the time of diagnosis, peripheral lesions were significantly larger than spinal (59 m3 vs 13 cm3) and brachial plexus lesions (15 cm3). Distinct growth patterns were seen with both distal peripheral nerve and spinal lesions; 34/82 peripheral nerve lesions had fast growth (β = 0.176%/day), and 48 had slow growth (β = 0.021%/day; P < .01). Spinal schwannomas similarly had 30 fast-growing (β = 0.229%/day), 16 moderate-growing (β = 0.071%/day), and 63 slow-growing (β = 0.022%/day; P = .03) subtypes. The brachial plexus had relatively homogeneous growth patterns (β = 0.065%/day). Females had 2.9 times greater odds of having the fast-growing subtype. CONCLUSION: Distinct growth patterns were seen in extracranial sporadic schwannomas based on tumor location and patient demographics. Fast (>80% volume change per year) vs slow (5%-10% per year) tumor growth can often be ascertained within 2 follow-up images. Awareness of these patterns might have implications for patient counseling and therapeutic decision-making.