Vet at FirstVet answers:
Cryptorchid (one or both testicles have not descended to the scrotum) dogs have a 13 times increased risk of developing testicular cancer if the testicles are left in the abdomen. There is also an increased risk of testicular torsion if the testicles are in the abdomen. Testicular cancer is often benign in dogs, but the longer the testicles are in the abdomen, the larger the chance is of the tumour/cancer spreading. Testicular tumours can also produces hormones that affect the dog’s bone marrow, resulting in severe anaemia (lack of red blood cells).