Histopathology and indicators of borderline ovarian tumours with microinvasion in bitches

The authors present two cases of borderline ovarian tumours with microinvasion in bitches with variable clinical significance. The first case documents a four-year-old female Weimaraner diagnosed with a tumour on the right ovary during a veterinary check-up, using ultrasound (USG) examination, which was then surgically removed. Histological examination revealed a clear cell borderline tumour of the ovary with microinvasion. The second case is represented by a necropsy sample from a 52-month-old female German Shepherd who died a day before the planned hysterectomy due to undertreated pyometra. During necropsy, a developed bilateral ovarian tumour was found. An additional histological examination revealed a serous borderline tumour with microinvasion of both ovaries. This paper discusses the histopathological and clinical aspects involved in the prognosis of borderline ovarian tumours in bitches. This concerns the possibility of a change for a more aggressive behaviour of these tumours and their immunohistochemical profile, then the risk of implant metastases and, finally, the time point of diagnosis, intervention, and therapy. Even histologically verified well-differentiated forms of borderline ovarian tumours with microinvasion in bitches can show the variable clinical significance and, therefore, in similar cases, only a good or only a bad prognosis of the disease should not be expected.