Ovarian teratoma in a woodchuck (Marmota monax) with hepatocellular carcinoma: radiologic and pathologic features

BACKGROUND: Teratomas are germ cell neoplasms composed of a wide variety of tissues. In the woodchuck, only one testicular teratoma has been described in the literature. The objective of this report was to describe the radiologic and pathologic findings in a female woodchuck (Marmota monax) with an ovarian teratoma consisting of mature tissues originating from all three germ layers. CASE PRESENTATION: A 2-year-old female woodchuck that had been infected at birth with woodchuck hepatitis virus and subsequently developed hepatocellular carcinoma was incidentally discovered to have a mobile 6.6 × 4.8 × 4.7 cm abdominal mass on computed tomography (CT) imaging. The tumor was predominantly solid and heterogenous on CT with soft tissue, fat, and areas of dense calcification. The teratoma did not enhance with intravenous contrast administration. On ultrasound, the tumor was solid with heterogeneous echogenicity, reflecting the fat content and areas of calcification. Sonolucent areas were present that may have represented cysts. There was heterogeneously increased signal on T1-weighted magnetic resonance imaging (MRI) and heterogeneous hyperintensity in T2-weighted imaging. Fat was evident within the tumor. At necropsy, the tumor was attached to the distal end of the right uterine horn. Histopathology showed mature tissue types representing all three germ layers. CONCLUSIONS: Ovarian teratoma should be considered in the differential diagnosis of ovarian or abdominal masses in woodchucks. The tumor displayed mature tissue derived from all three germ layers. CT, ultrasound, and MRI findings were presented in detail and matched the typical imaging appearance of teratomas.