A 28-year-old male presented with diffusely metastatic epi thelioid-type peritoneal mesothelioma (MPeM)...Next generation sequencing with a 468 gene panel (320X coverage) revealed...tumor muta tional burden (TMB) of 1.8 mutations/megabase, including loss of function pathogenic mutations in BAP1 (V99M: c.295G > A) and NF2 (R34:1c.1021C >T), as well as broad copy number loss on chromosome arms 14q and 19q. The patient’s disease was initially unresectable, and he received four treatments of cisplatin and pemetrexed with an initial decrease in peritoneal carcinomatosis. The patient also received normothermic postoperative intraperitoneal chemotherapy with alternating cisplatin and mitomycin for 3 total cycles. The patient exhibited disease recurrence with increased bulky carcinomatosis after 3 years of active surveillance and received 8 cycles of pemetrexed/cisplatin without response. The patient resumed carboplatin (500 mg/m2 ) and pemetrexed (460 mg) for 2 cycles without response.