PATH-02. TWO CASES WITH MULTIPLE HYBRID NERVE SHEATH TUMORS WITH ERBB2 MUTATIONS
Abstract Hybrid nerve sheath tumors are new disease entity incorporated in WHO classification of tumors of the central nervous system 2016 version that includes benign peripheral nerve sheath tumors with combined features of more than one conventional type. Ronellenfitsch et al recently reported one case with ERBB2 D769Y mutation with good clinical response to lapatinib in 2020. We report two cases with imaging findings of multiple peripheral nerve sheath tumors with pathology proven hybrid nerve sheath tumors with ERBB2 mutations. Patient 1 has neurofibroma/schwannoma hybrid nerve sheath tumor with ERBB2 D769Y mutation and patient 2 has plexiform neurofibroma/schwannoma hybrid nerve sheath tumor with ERBB2 V777L mutation. Both of our patients have similar clinical features with adult-onset multiple peripheral nerve sheath tumors without other systemic features of neurofibromatosis type1 or vestibular schwannomas or family history. Hybrid nerve sheath tumors are newly recognized disease and more than half of the cases have multiple peripheral nerve sheath tumors, suggestive of tumor syndrome. Patients with multiple peripheral nerve sheath tumors without systemic features of neurofibromatosis type1 or vestibular schwannomas should be screened for genetic/molecular tests including ERBB2 mutation that might provide treatment options for these patients.