Schwannomatosis is a disease characterized by multiple schwannomas. Neurofibromatosis type II (NF2), an autosomal dominant inherited disease associated with auditory nerve tumors, neurofibromas, and schwannomas, is a representative example of shwannomatosis, and NF2 gene is the causative gene of the disease. Recently, LZTR1 and SMARCB1 have been reported as causative genes of schwannomatosis without auditory nerve tumor. Several previous reports demonstrated that hybrid schwannoma and neurofibroma was observed in the patients with NF2. While it is not cleared whether the patients with schwannomatosis caused by mutations of LZTR1 or SMARCB1 have hybrid schwannoma and neurofibroma. In this study, we initially performed mutation analysis of two patients with hybrid schwannoma and neurofibroma. A novel frameshift mutation c.1844delA in the LZTR1 gene was identified in one patient, however the other patient did not have any mutations. The patient with LZTR1 mutation had a history of removal surgeries of two schwannomas, and the other patient did not have a history of schwannoma and a family history. Therefore, we demonstrated that the patient with schwannomatosis caused by a mutation of LZTR1 had hybrid schwannoma and neurofibroma. While we also showed that hybrid schwannoma and neurofibroma was not necessarily schwannomatosis. We then focused on the frequency of hybrid schwannoma and neurofibroma in the samples previously diagnosed as schwannoma. We are analyzing total 66 samples of schwannomas, and trying to search somatic mutations of NF2, LZTR1 and SMARCB1 in the samples of hybrid schwannoma and neurofibroma.

ESDR157 - Analysis of the hybrid schwannoma and neurofibroma including a case report of schwannomatosis caused by a mutation in the LZTR1 gene

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