Objective: We hypothesized that ovarian tumors without oviductal involvement would not express the oviductal protein ovalbumin, the major protein found in the magnum of the hen's oviduct.
Methods: On the basis of gross visual examination, tissues samples were removed from hens determined to have ovarian tumors and were processed, embedded in paraffin, sectioned, mounted on glass slides, and stained with hematoxylin and eosin. Ovarian tumors and other peritoneal lesions were evaluated histologically. Paraffin sections of ovarian and oviductal tissue were deparaffinized and evaluated for the protein expression of ovalbumin, proliferating cell nuclear antigen (PCNA), and progesterone receptor (PR).
Results: Hens with ovarian adenocarcinoma without (n = 10) or with (n = 6) oviductal involvement were positive for ovalbumin in the ovary. Ovary sections from normal hens (n = 9) were negative, and oviductal sections from normal hens (n = 3) were positive for ovalbumin. Expression of PCNA protein was abundant in all ovarian tumors (16 of 16). Oviductal epithelial cells strongly expressed PCNA protein. Expression of PR was observed in 9 of 14 ovarian tumors.
Conclusion: The presence of ovalbumin in ovarian tumors in the absence of any oviductal involvement suggests that ovarian tumors dedifferentiate during the disease process and thereby resemble serous-type ovarian tumors in women.