In a recent study of 82 dogs with high-risk mast cell tumours (Patnaik grade 3, Kiupel high grade, mitotic index >5, lymph node metastasis, recurrent mast cell tumour, recent rapid growth or ulceration or high-risk locations), abdominal ultrasound was found to be a poor predictor in detecting metastasis (i.e. cancer spread) to the spleen and liver.

Unfortunately, when there is evidence of metastasis to the spleen or liver, the median (average) survival times are between one and 3.5 months. However, this study found that dogs that had early evidence of metastasis to spleen or liver had median survival times of 10.5 months with adequate local control (i.e. surgery) and chemotherapy. Moreover, one in five dogs with early evidence of metastasis to the spleen or liver lived for more than 500 days. 

Therefore, ultrasound-guided fine-needle aspirates for cytology of the liver and spleen is recommended in all dogs with high-risk mast cell tumours, even if both the spleen and liver look normal on ultrasound.