Peritoneal papillary mesothelioma in situ: BAP1 mutation with indolent behavior for 15  years

We describe the 15-year long course of a PMIS in an adult male in which inactivating mutations ofBAP1, encoding BRCA1 associated protein 1 (BAP1), were identified. Tumor samples were obtained on 2 occasions more than 8y apart. In both samples, the tumor cells were bland, with occasional focal infiltration into the stalks of larger papillary lesions. However, no invasion into subserosal adipose tissue was identified. In both samples the tumor cells did not express nuclear BAP1. Comprehensive genomic analysis of the initial tumor sample revealed a somatic inactivating mutation inBAP1 (predicted effect, Y223*) and a somatic variant ofIRS2 (A701_V702insAA). An additional inactivating mutation inBAP1 (predicted effect, T69fs*5) was detected in the later sample. The patient did not receive any treatment and is still alive 15  years after initial presentation. Our experience supports the view that peritoneal PMIS may follow an indolent course for many years and prompts the question whether these tumors should uniformly be treated aggressively.
Source: Virchows Archiv - Category: Pathology Source Type: research