Immunohistochemical findings of carcinosarcoma of the right ovary were as follows: CK fraction (+), vimentin fraction (+), CK5/6 foci (+), p16 (+), p53 in approximately 70% (+), WT-1 foci (+), ER foci (+), PR part (+), Her-2 (1+), CK7 fraction (+), CK20 foci (+), CD99 fraction (+), CD10 fraction (+), CD56 foci (+), c-kit foci (+), SMA part (+), desmin foci (+), PD-L1 (-), SALL4 (-), OCT3/4 (-), p63 (-), p40 (-), D2-40 (-), inhibin (-), PLAP (-), CD30 (-), and Ki67 hotspot in approximately 80% (+). Here, CD99 is linked to carcinosarcoma.