Ectopic pregnancy with associated gestational choriocarcinoma in a California sea lion (Zalophus californianus)

A wild-born, captive-reared, 14 yr old, primiparous female California sea lion Zalophus californianus presented for anorexia of 14 d duration and abdominal distention. Routine complete blood cell count revealed leukocytosis with a neutrophilia, and serum chemistry revealed hypoalbumenemia and hyponatremia. Treatment with broad spectrum antibiotics and non-steroidal anti-inflammatories were started, but the animal continued to decline. Abdominal radiographs revealed a mature mineralized fetal skull and spine in the caudal abdomen and abdominal ultrasound revealed ascites but could not confirm the fetus. The patient was taken to surgery where a full term fetus was found outside of the uterus but within the fetal membranes, representing a secondary ectopic pregnancy. The patient passed away during surgery and was taken to necropsy. Gross necropsy revealed a diffuse peritonitis with yellow deposits over the serosal surfaces of the abdominal organs. The uterus appeared intact grossly and the ovaries appeared abnormal. The mesenteric, renal, and sub-lumbar nodes were enlarged and edematous. 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 locally as well as to the liver, spleen and lung. Choriocarcinoma is a highly malignant trophoblastic neoplasm that is rare in domestic animals. This case represents, to the authors' knowledge, the first report of gestational choriocarcinoma causing secondary ectopic pregnancy in a California sea lion and presents questions regarding pregnancy monitoring and management in a population of captive, minimally trained California sea lions.