Conversely, OCS may be conceptualised as an extreme form of CCNE1-gained HGSOC, though it is important to note that not all OCS harbour this event, and that not all OCS have carcinomatous components of high grade serous type [1]; CCNE1 gain is not known to occur frequently in endometrioid ovarian carcinoma [12, 31, 32]. Here, CCNE1 is linked to ovarian endometrioid carcinoma.