Metastatic adenocarcinoma in a layer chicken flock (case report)

The laying hen possesses a single functional ovary, which undergoes ovulation at a high rate during its lifespan. In hens, spontaneous tumors of the ovary and, less frequently, of the oviduct, are common. More than 80% of commercial laying hens develop ovarian tumors by the time they are 2 years of age. Ovarian tumors usually don't become apparent until their growth is well advanced. The bird may have a history of egg binding or oviductual prolapse. They may also have problems associated with egg laying, such as increased infections, soft-shelled, shell-less and other abnormal eggs, and generalized signs of lethargy/depression. There is no available cure for ovarian tumors in hens. Treatment options are aimed at stopping egg production and to minimize risk of future egg-related infections such as egg yolk peritonitis. These include hormonal implants or, as a last resort, "spaying". There are also a number of different natural herbs which have shown some benefit. It showed that hens fed a flaxseed-enriched diet for one year experienced a significant reduction in late-stage ovarian tumors. Reproductive tumors can reduce egg production rates and lead to an overall decline in general health in the laying hen. Usually viral agents such as: herpes and retro viruses cause tumors in birds. Most researches on avian tumors has been done in viral agents cases, because of their economic importance and because these studies serve as a model for cancer studies in women. Ovarian epithelial cancer is the fifth leading cause of cancer deaths and the most deadly reproductive tract cancer in women. Domestic poultry is the most appropriate animal model for studying ovarian cancer in women. No other animal develops spontaneous ovarian tumors at comparable rates to the chicken which can exceed 35% depending on the genetic background (i.e., strain, age, and number of eggs produced by the flock. Moreover, the pathology and progression of the disease resembles that in humans in several respects. Leiomyoma and oviduct adenocarcinoma are the most common tumors of the reproductive tract in laying hens. Oviduct adenocarcinomas usually originate from the magnum of the oviduct, and occasionally arise from the infundibulum and uterus. Adenocarcinomas in poultry are among the groups of unknown etiology tumors, but a relationship between high egg production and the prevalence of oviduct tumors has been shown. 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.

The present communication, reports a metastatic adenocarcinoma in an 80 week old commercial layer chicken in second-cycle egg production in Mazandaran province, Iran. Eight dead layer hens were referred to division of avian diseases. On necropsy examination, mesentery and serosal surface of intestine was studded with grayish white nodules. Ovary contained varying sizes of multiple single to lobulated firm, cauliflower-like, grayish white nodules. Also, yellowish transparent ascites were seen in some cases. Tissue samples were taken and placed in 10% neutral buffered formalin, then, were placed in cassettes, dehydrated in ethanol, cleared with xylene, and embedded in paraffin wax. Sections were made at 5 µm thickness on glass microscope slides and stained with standard haematoxylin and eosin (H&E) and then examined by light microscopy.

Microscopically, cuboidal neoplastic cells were arranged in acinar and tubular pattern in the serosal layer of intestine. The cells appeared as variable sized cuboidal cells with indistinct cell borders, eosinophilic granular cytoplasm, round nuclei, indistinct nucleoli and fine chromatin granules. Intestine nodules showed neoplastic cells and structures similar to those of the ovary tumor. These adenocarcinomas were encountered in 80-week-old White Leghorn hens, which tallies with the reviewed published findings that ovarian and oviductal adenocarcinomas are among the most frequently encountered tumors in older White Leghorn hens. Laying hens are the only animals that develop spontaneous ovarian cancer similar to humans. In the present case, according to histological appearance of the growth in the ovary, the tumor was diagnosed as an ovarian adenocarcinoma with metastasis on the whole of intestines. In this study, ascites was observed in the abdominal cavity of birds; the tumor obstructed the lymph flow and thus could lead to ascites. Prolonged egg production period may be one of the important causes of involvement with this type of tumor. Continuous secretion of gonadotropins can over-stimulate estrogen-sensitive epithelial cells in the oviduct and cause tumor cells to develop.

Neoplastic diseases, regardless of their cause or the organ affected, have economically impact; therefore, it is important to report these cases.Keywords: Layer chicken, Ovary, Intestine, Adenocarcinoma, Metastasis.