Seromucinous carcinoma of the peritoneum (A–E) and clear-cell carcinoma of the ovary (F–H). A, Macroscopic view of an oligocystic lesion on the peritoneum; B, At lower magnification, papillary structures with edematous stroma are observed; C, At higher magnification, fused irregular glands show stromal invasion, while several tumor cells contain mucus (inset); D, Endometriosis observed on the background cyst wall; E, Components of a borderline seromucinous tumor present; F, Clear-cell carcinoma shows tubulo-cystic, papillary, and solid structure (left side) accompanied by endometriosis on the adjacent cystic wall (arrow head); G, Clear-cell carcinoma; H, At higher magnification, endometriosis and aggregation of hemosiderin-laden macrophages are observed. All microscopic slides (B–E and F–H) are hematoxylin and eosin-stained.