The molecular pathology of ovarian serous borderline tumors

Molecular studies in ovarian serous borderline tumors (OSBTs) have been used to understand different aspects of this neoplasm. (i) Pathogenesis, Kras and Braf mutations represent very early events in the tumorigenesis of OSBT as both are detected in serous cystadenomas associated with OSBTs. In contrast, serous cystadenomas without OSBTs do not show Kras or Braf mutations. In OSBTs, Kras mutations range from 17% to 39.5%, while Braf mutations range from 23% to 48%. The former is comparable with the range of Kras mutations in ovarian low-grade serous carcinomas (OLGSCa), 19%-54.5%. In contrast, Braf mutations in OLGSCa range from 0% to 33%. Serous cystadenomas appear to progress to OSBT due to a Braf mutation, but this mutation is rarely involved in the progression to OLGSCa. OSBTs with Braf mutation are associated with cellular senescence and up-regulation of tumor suppressor genes. In contrast, OSBTs without a Braf mutation may progress to OLGSCa due to Kras mutation or some other genetic alterations. (ii) The relationship between OSBTs and the extraovarian disease, a monoclonal versus mutifocal origin? This is still matter of debate as studies using different techniques have failed to settle this controversy. (iii) Biological behavior, Braf mutations appear to have a protective role against the progression of OSBT to OLGSCa, while Kras mutations are commonly seen in cases of OSBT that recurred as LGSCa. Nevertheless, LGSCa as a recurrence of an OSBT can originate from OSBTs with or without detectable Kras mutations. Also, it appears to be an association between Kras G12v mutation and a more aggressive phenotype of OSBT that recurred as LGSCa. (iv) Actionable targets, currently there are limited data. It has been reported that cancer cell lines with Kras G12v mutation are more sensitive to selumetinib than cell lines with wild-type Kras.