The genetic alterations most frequently seen in clear cell carcinomas (CCCs) of ovary include ARID1A, PIK3CA, and PTEN mutations. ARID1A mutations lead to loss of expression of BAF250a protein. These alterations are also present in the adjacent endometriotic foci further linking them to the histogenesis of CCCs. Some cases are associated with Lynch syndrome (germline mutations in MSH2 gene). The image shows a necrotic focus in a case of CCC of the ovary.