Large hydatidiform mole: an unusual finding in a calving cow.

CASE HISTORY: A 4-year-old Friesian cow was reported to be having difficulty calving. Palpation by farm staff identified a large mass in the uterus, but no calf.

CLINICAL FINDINGS: Veterinary examination per vaginam identified a small calf and a large immobile mass. The calf was delivered by Caesarean section, but the mass could not be extracted during surgery. Biopsying the mass resulted in the loss of a large amount of fluid from it, but it remained immovable; overnight, the mass was expelled per vaginam. Gross and histological examination of the mass showed it to comprise multiple oedematous chorionic villi, prominent stratified trophoblast, undifferentiated sub-trophoblastic mesenchymal tissue that contained adipose tissue, blood vessels and bizarre striated muscle fibres, as well as irregular cisterns in the centre. No recognisable embryonic or fetal tissue was found.

DIAGNOSIS: Based on the gross and histological appearance it was concluded the mass was a complete hydatidiform mole.

CLINICAL RELEVANCE: This is a rare, poorly understood condition of cattle. This is believed to be the first report in a cow in New Zealand.