This study investigates the genetic basis of Ovarian Clear Cell Carcinoma (OCCC), an aggressive form of ovarian cancer. The authors sequenced the exomes of eight OCCC tumors after purifying cancer cells and identified four genes with mutations in at least two tumors: *PIK3CA*, *KRAS*, *PPP2R1A*, and *ARID1A*. *PIK3CA* and *KRAS* are well-studied oncogenes, while *PPP2R1A* and *ARID1A* are novel candidates. The mutations in *PPP2R1A* are clustered and suggest it functions as an oncogene, whereas the mutations in *ARID1A* are distributed throughout the coding region and are predicted to inactivate the protein, suggesting it acts as a tumor suppressor. In a total of 42 OCCC cases, 7% had mutations in *PPP2R1A*, and 57% had mutations in *ARID1A*. These findings indicate that chromatin remodeling, particularly through *ARID1A*, contributes to the pathogenesis of OCCC. The study highlights the importance of identifying specific tumor suppressor genes like *ARID1A* in understanding the genetic and epigenetic changes in cancers.This study investigates the genetic basis of Ovarian Clear Cell Carcinoma (OCCC), an aggressive form of ovarian cancer. The authors sequenced the exomes of eight OCCC tumors after purifying cancer cells and identified four genes with mutations in at least two tumors: *PIK3CA*, *KRAS*, *PPP2R1A*, and *ARID1A*. *PIK3CA* and *KRAS* are well-studied oncogenes, while *PPP2R1A* and *ARID1A* are novel candidates. The mutations in *PPP2R1A* are clustered and suggest it functions as an oncogene, whereas the mutations in *ARID1A* are distributed throughout the coding region and are predicted to inactivate the protein, suggesting it acts as a tumor suppressor. In a total of 42 OCCC cases, 7% had mutations in *PPP2R1A*, and 57% had mutations in *ARID1A*. These findings indicate that chromatin remodeling, particularly through *ARID1A*, contributes to the pathogenesis of OCCC. The study highlights the importance of identifying specific tumor suppressor genes like *ARID1A* in understanding the genetic and epigenetic changes in cancers.