Testicular tumours are common in older entire male dogs, and a frequent cause for presentation at the local veterinary clinic. They can affect one or both testes, and it is not unusual to find more than one tumour in a testis. Testicular tumours are more frequently found in the right testis compared to the left. Cryptorchidism is also a risk factor for their development.
Clinical symptoms may include the palpation of a mass in one or both testes, asymmetrical testes, scrotal changes and poor reproductive performance. Some testicular tumours (mostly Sertoli cell tumours) may be associated with the production of hormones that produce distinct clinical syndromes (see case report). Rarely they may present as an acute abdomen due to torsion.
The most common testicular tumour is the interstitial cell tumour (a.k.a. Leydig cell tumour), followed by seminoma and lastly Sertoli cell tumour. Most of these are benign and can be cured by complete excision however rare malignant varieties do exist.
Diagnosis of most testicular tumours is relatively straight forward and generally involves cytology and/or histopathology. Castration is regarded as the treatment of choice and is generally curative for most cases.
Non-neoplastic testicular lesions can sometimes be mistaken for testicular tumours and these include testicular necrosis due to a previous suspected torsion, and testicular atrophy/hypoplasia of unknown cause. Sometimes scrotal tumours may be mistaken for testicular tumours. Infectious epididymitis and orchitis are seemingly common and mostly thought to be due to the traumatic implantation of bacteria. An important differential for this is Brucella canis which should be considered in any dog with any international travel history, and if concerned, MPI should be notified of such cases.
(Refer to That’s just nuts! for a related case write up)