Abstract
BACKGROUND: Teratomas are rare types of germ cell neoplasms composed of various differentiated or undifferentiated tissues. CASE DESCRIPTION: A 25-week-old female control FVB /n mouse in a 4-week toxicity study presented abdominal distension and poor body condition. It was euthanized, and the necropsy examination revealed a large mass connected to the tip of the right uterine horn, occupying the entire abdominal cavity. Microscopically, this mass showed areas of epidermal differentiation, with laminated keratin and sebaceous glands, differentiation into respiratory and digestive epithelium, cartilage, bone, and extensive areas of differentiation into the nervous tissue, being classified as an ovarian teratoma. CONCLUSION: As far as authors know, the occurrence of ovarian teratomas in the FVB/n mouse strain has never been previously described.