The most common cell types in clear cell carcinomas of the ovary are clear cells and hobnail cells. Clear cells line glandular structures or can be arranged in solid nests, clusters, and sheets (as seen here). They are polygonal in shape, have distinct cytoplasmic borders, and contain clear cytoplasm (due to glycogen; PAS-positive – diastase sensitive). The nuclei are slightly enlarged. Mitotic activity is not appreciably increased.