Abstract
A wild-born, captive reared, fourteen year old, primiparous female California sea lion presented for anorexia of 14 day duration and abdominal distention. Routine complete blood cell count revealed leukocytosis with a neutrophilia, and serum chemistry revealed hypoalbuminemia and hyponatremia. Treatment with broad spectrum antibiotics, and NSAIDs was started, but the animal continued to decline. Further diagnostics, including abdominal radiographs and abdominal ultrasound, revealed ascites and a calcified mass in the caudal abdomen. The patient was taken to surgery where a full term fetus was found outside of the uterus but within the fetal membranes. The patient passed away during surgery and was taken to necropsy.
Gross necropsy revealed a diffuse peritonitis with fibrin along the serosal surfaces of most of the abdominal organs. Hepatomegaly and splenomegaly were identified. The uterus appeared intact grossly and the ovaries were dark red, enlarged and appeared to have localized abscessation. The mesenteric, renal, and sub-lumbar nodes were enlarged. Histopathology revealed choriocarcinoma in the right uterine horn with evidence of chronic uterine rupture and protrusion of the placental tissue into the abdomen. The choriocarcinoma had metastasized to the liver, adjacent lymph nodes, peritoneum and the lymphatics of the lung, spleen and liver. Fluid analysis from the abdominal fluid revealed a septic appearing mixed cell exudate with clusters of exfoliating carcinoma cells.
Choriocarcinoma is a highly malignant trophoblastic neoplasm that can occur after a pregnancy, as a component of a germ cell tumor, or in association with a poorly differentiated somatic carcinoma.3 Choriocarcinoma is rare in domestic animals and occurs in approximately 1 in 20,000 to 40,000 human pregnancies.3,5 Gestational choriocarcinoma occurs when the neoplasia is derived from pregnancies, induced or spontaneous abortions, ectopic pregnancies, and term or preterm deliveries.3 In this case the choriocarcinoma appears to be related to the pregnancy. Reports of neoplasia in California sea lions are increasing in number and encompass a wide range of neoplasms.1,2 An 18% prevalence of neoplasms has been reported in California sea lions that stranded live along the central California coast. The predominant neoplasm was a poorly differentiated carcinoma of urogenital origin.2,6 This case represents, to the authors' knowledge, the first report of gestational choriocarcinoma in a California sea lion and presents questions regarding pregnancy monitoring and management in a population of captive, minimally trained California sea lions.
Acknowledgments
We would like to thank the veterinary staff and the marine mammal trainers at Six Flags Discovery Kingdom for all of their hard work and patience throughout this case. We would also like to thank the University of California, Davis VMTH anatomic pathology service for their work on this interesting case.
* Presenting author
Literature Cited
1. Dierauf LA, Gulland FMD (eds). 2001. CRC Handbook of Marine Mammal Medicine. New York: CRC press. P 527–528.
2. Gulland FMD, Trupkiewicz JG, Spraker TR, Lowenstine LJ. 1996. Metastatic carcinoma of probable transitional cell origin in 66 free-living California sea lions (Zalophus californianus). Journal of Wildlife Diseases 32:250–258.
3. Hoffner L, Surti U. 2012. The genetics of gestational trophoblastic disease: a rare complication of pregnancy. Cancer Genetics 205:63–77.
4. McGavin MD, Zachary JF. 2007. Pathologic Basis of Veterinary Disease. PA: Mosby Elsevier. P 1289.
5. Monchek R, Wiedaseck S. 2012. Gestational trophoblastic disease: an overview. Journal of Midwifery and Women's Health 57:255–259.
6. Ylitalo GM, Stein JE, Hom T, Johnson LL, Tilbury KL, Hall AJ, Rowles T, Greig D, Lowenstine LJ, Gulland FMD. 2005. The role of organochlorines in cancer-associated mortality in California sea lions (Zalophus californianus). Marine Pollution Bulletin 50:30–39.