Testicular Tumors


Testicular tumors are considered very common among intact male dogs. In fact, up to 27% of unneutered male dogs will eventually develop one or more testicular tumors. In total, they're estimated to account for at least 4% to 7% percent of all tumors found in male dogs.

A variety of tumors affect the testicles. Indeed, it's common for more than one tumor type to affect the same patient. A full one third of all testicular tumor patients will be diagnosed with more than one tumor type,

The most common testicular tumors include the following:

Interstitial cell tumors (50%): These common testicular tumors tend to be small and benign. They rarely spread or act aggressively.

Seminomas (42%): This tumor arises from the germinal epithelium (the cells of the testicle that produce sperm). They may occur on one side or on both (in approximately 18% of cases). They are more common in chryptorchid males (those with undescended testicles). Like interstitial cell tumors, they don't tend to spread, but some may defy the norm and metastasize or invade local tissues in aggressive ways.

Sertoli cell tumors (8%): This tumor type is more common in undescended testicles (found in the abdomen or groin) and tends to spread more aggressively than others.

Others: Though considered rare, embryonal carcinomas, lipomas, fibromas, hemangiomas, chondromas and teratomas are also possible varieties of testicular tumors.

As with most cancers, the cause of testicular tumors is unknown. However, since some of these tumors have been correlated with the presence of undescended testicles (cryptorchidism) as well as prostatic disease, the influence of testosterone is unquestionable.

Affected dogs tend to be older (over six years of age).

Note: Because they've been so well studied, seminomas are discussed in more detail in a separate article within this library.

Symptoms and Identification

The typical signs of testicular tumors include swelling of one or both testicles, enlargement of the scrotum, and infertility (noted in breeding animals). In the case of some rare, estrogen-producing seminomas, signs of feminization may become evident.

Identification of testicular tumors may involve one or all of the following approaches:

  • Scrotal palpation (these masses are typically easy to palpate)

  • Rectal examination (to feel intra-abdominal masses)

  • Abdominal X-rays

  • Abdominal ultrasound

  • Exploratory surgery (to observe and possibly biopsy the nearby lymph nodes for possible tumor spread)

  • Sperm analysis (sperm abnormalities can result from these tumors)

  • Chest X-rays

  • Biopsy upon castration (fine-needle aspiration and biopsy aren't typically recommended before castration as these can result in permanent damage to the testicular tissue that may obscure disease progression)

Most diagnoses, however, rely on simple scrotal palpation. Biopsy upon castration is required for a definitive diagnosis. Advanced diagnostics are required in cases where the possibility of aggressive behavior exists.

Affected Breeds

While all breeds of dogs may suffer from testicular tumors, some are clearly predisposed:


Sertoli cell tumors:


Most testicular tumors are considered highly treatable. This is especially true of the interstitial cell tumors and seminomas -- the latter, as long as they behave non-aggressively (as most do).

Castration is the treatment of choice. This, of course, includes the removal of any undescended testicle. In these cases, castration may be a bit more complicated than for the average dog since dogs with testicular tumors may require the removal of the overlying scrotal skin.

Radiation therapy combined with chemotherapy has successfully been used in dogs with metastatic or invasive tumors to yield a complete clinical cure.

Veterinary Cost

The veterinary cost of testicular tumors is typically relegated to the tests and surgery required to identify and treat them, respectively.

Because most cases are fairly straightforward, expenses tend to run under $500 for diagnosis and under $1,000 for treatment. In metastatic or otherwise complicated cases, however, expenses can increase dramatically depending on the need for advanced surgery techniques, radiation or chemotherapy.


There is no known means of prevention for testicular tumors, save early castration. The pros and cons of castration should be discussed with a veterinarian, ideally in advance of adolescence. Since cryptorchid pets are more at risk, they should ideally be castrated early. Furthermore, given the hereditary nature of testicular tumors, affected dogs should be removed from the gene pool immediately.


Bush, J.M. Gardiner, D.W. Palmer, J.S. Rajpert-DeMeyts, E. Veeramachaneni, D.N.R. Testicular germ cell tumours in dogs are predominantly of spermatocytic seminoma type and are frequently associated with somatic cell tumours. International Journal of Andrology. Volume 34, Issue 4pt2, pages e288-e295, August 2011

Dhaliwal RS, Kitchel BE, Knight BL, et al. Treatment of aggressive testicular tumors in four dogs. J Am Anim Hosp Assoc 35: 311-318; 1999.

Grieco V, Riccardi E, Greppi GF, et al. Canine testicular tumours a study on 232 dogs. J. Comp Path 138: 86-89, 2008.

Looijenga LH1, Olie RA, van der Gaag I, van Sluijs FJ, Matoska J, Ploem-Zaaijer J, Knepfle C, Oosterhuis JW. Seminomas of the canine testis. Counterpart of spermatocytic seminoma of men?Lab Invest. 1994 Oct;71(4):490-6.

McDonald RK, Walker M, Legendre AM, et al. Radiotherapy of metastatic seminoma in the dog. J Vet internal Med 2:103-107, 1988.