The most frequent tumor of the reproductive system is adenocarcinoma of the oviduct. Neoplastic cells are shed from tumors in the oviduct into the abdominal cavity. They implant on the ovary, pancreas, and other viscera and produce multiple, hard, yellow nodules. They may block lymph return and result in ascites. The incidence increases with age, and this tumor may be a frequent cause of death after 2 years. Affected hens are condemned at processing.
Leiomyoma of the broad ligament is an estrogen-induced hypertrophy of the smooth muscle of the broad ligament. It is benign and is an incidental finding at necropsy or processing.
A variety of ovarian and testicular tumors has been described. Marek disease is a common cause of tumors of the ovary.