Based on diagnostic classifications, recurrent alterations in TP53, MYC, PIK3CA, and KRAS are consistently observed across epithelial and germ cell ovarian tumors, whereas non-epithelial subtypes such as sex cord–stromal tumors (SCSTs) and small-cell carcinoma of the ovary, hypercalcemic type (SCCOHT), are predominantly associated with ARID1A and SMARCA4 mutations, respectively. This evidence concerns the gene PIK3CA and ovarian small cell carcinoma.