Molecular Analysis of a Patient With Neurofibromatosis 2 (NF2) and Peritoneal Malignant Mesothelioma

Neurofibromatosis type 2 (NF2), an inherited disorder associated with multiple inherited schwannomas, meningiomas and ependymomas is caused by an autosomal dominant, likely loss of function germline mutation of the NF2 gene. Interestingly, biallelic NF2 gene inactivation is one of the most common mutations associated with the development of malignant mesothelioma (MM), a highly fatal malignancy that arises in the pleura and less frequently in the pericardium, peritoneum, and tunica vaginalis. It has been proposed that NF2 patients could potentially be at increased risk of developing MM. However, patients with inherited NF2 rarely develop MM. To date, only 2 cases describing patients diagnosed with both have been reported in the literature. Here, we describe the third case and for the first time, also provide molecular evidence that a "second hit" involving a somatic mutation is likely required to trigger the development of MM in this rare cohort. In our patient diagnosed with NF2 at age 25 who developed an aggressive peritoneal MM 15 years later, we identified a germline NF2 mutation and somatic mutations including BAP1. Of clinical relevance, our case supports a germline NF2 mutation may not necessarily be more susceptible to develop mesothelioma without a "second hit" mutation.