Figure 1.

Gross morphology of normal and malignant ovaries in laying hens. (A) Fully functional normal ovary in a laying hen. Laying hens ovulate and subsequently lay eggs once a day for 5 or 6 days in a week in a continuous manner and then take a pause for 1 day before laying resumes. Thus, the ovary in a fully functional laying hen contains a set of multiple large and growing preovulatory follicles arranged in a hierarchy of sizes (F1–F5). The largest follicle (F1) is destined to ovulate soon and then the second largest follicle (F2) becomes F1 and a small growing follicle is recruited from the ovarian stroma to the hierarchy to maintain the laying rates. (B) Ovarian tumor at an early stage in a hen showing solid tumor mass (arrows) limited to the ovary. (C) Ovarian tumor at a late stage. The2 tumor (Tu) appears like a cauliflower and has metastasized to other organs with accompanied profuse ascites (*).