are easily prevented through routine castration of male dogs. Castration in young dogs prevents aggression, roaming, urine marking, and a variety of other unwanted male
behaviours. The surgery is safe and relatively inexpensive, and in the long run saves the owner money. Dogs that are used for breeding can be castrated when they are no longer used for breeding. Dogs that are cryptorchid should always be castrated and the owner should insist that both testicles be removed. Since cryptorchidism is considered to be an inherited trait, cryptorchid dogs should never be used for breeding. Because the retained testicle is 13 times more likely to develop a
tumour, it should always be removed.
Testicular tumours are considered one of the most common tumours
in older intact male dogs. Some of these tumours are found within the abdominal cavity if the testicle did not descend into the scrotum. Some of these
tumours may produce excessive estrogens which causes hair loss, nipple enlargement and a stripe of inflammation on the prepuce. The prognosis tends to be
favourable, as only 10% of these spread.
What are testicular tumors?
Testicular tumors are considered one of the most common tumors in older intact male dogs. The overall incidence in dogs is not very high because most dogs dogs are castrated (neutered) at a young age. The three most common types of testicular tumors are Sertoli cell tumors, interstitial (Leydig) cell tumors, and seminomas. About one third of dogs that develop a tumor will have more that one of these types of tumors present. Other types of testicular tumors (i.e. embryonal carcinoma, lipoma, fibroma, hemangioma, chondroma, teratoma) can occur, but are rare.
The current cause of testicular tumor development is unknown. Although they are most common in intact older male dog (>10 years), they can occur in intact males of any age and breed. Male dogs that have one or both testicles that have not descended from the belly cavity are much more likely to develop a tumor than dogs with normal (scrotal) testicles.
Tumors of normal descended, or scrotal, testicles are usually benign while those still located in the abdomen are much more likely to be malignant. Testicles retained in the abdomen are predisposed to the development of Sertoli cell tumors and seminomas. The tumor is slow to metastasize and the common site of spreading include lymph nodes.
Testicular tumors produce excessive hormones such as estrogen or testosterone.
Sertoli cell tumors have a higher rate of spread than other testicular tumors and are more common in cryptorchid testes. Dogs affected with these tumors show swelling of the testicular or scrotal area.
Interstitial (Leydig) cell tumors are benign and small. Dogs affected with these tumors show very few symptoms and the tumors are usually incidental findings.
Seminomas arise from the cells of the testicle that normally produce sperm. The majority of seminomas are benign and they rarely spread. Seminomas may lead to signs of femal characteristics in a male dog. Most dogs are not ill, and many of these tumors are found during a routine physical examination.
Soft swellings in one or both testicles
Single enlarged testicle or asymmetric testicles
Generalized scrotal enlargement
Infertility in the breeding stud
Hair & Skin changes:
Symmetrical hair loss
Poor hair regrowth
Hyperpigmentation (darkening of the skin)
Stripe of red inflammation along the midline of the
Nipple elongation (see photo below right) Mammary
Preputial swelling and sagging
Testicular atrophy of the unaffected (non-cancerous
Prostatic atrophy or enlargement
Squatting to urinate
Reduced sex drive
Attraction of other male dogs
Presentation - see above clinical signs
A thorough physical examination including palpation of
the testicles; the stripe of inflammation seen along the
prepuce (arrow in the photo to the right) is classic for
an estrogen producing tumor
Complete blood count (CBC)
Urinalysis +/- culture and sensitivity
Chest and abdominal radiographs (x-rays)
Abdominal and scrotal ultrasound
Fine needle aspiration or biopsy
Biopsy of the removed testicle
Surgery: Surgical castration or an abdominal exploratory
may be performed.
Chemotherapy and radiation therapy can be pursued if the
tumor has metastasized. Treatment of metastatic
disease should be pursued.
Anemia - High levels of estrogen can reduce the function
of the bone marrow which may lead to significant decreases
in the number of white blood cells, red blood cells, and
platelets. The patient is then at risk of developing
infections, anemia, and bleeding tendencies that can be
Occasionally testicular tumors may predispose the testicle
to twist, called testicular torsion. The twisting of
the testicle will cause sudden swelling of the scrotum and
If the tumor has spread and is an estrogen producing tumor;
these clinical signs do not disappear even though the
cancerous testicle was removed.
Complications following properly performed castrations are
rare. Potential complications may include incisional
problems such as swelling, infection, bleeding into the
scrotum and self-mutilation of the incision.
Aftercare (Home Care)
Animals undergoing surgery are monitored for pain,
hemorrhage, and infection. At home the incision and
scrotum will need to be checked twice daily for any signs of
swelling, redness, or discharge. If a significant
amount of discharge from the incision is present or
swelling, infection may be present and antibiotic therapy
will need to be prescribed.
A recheck in 10-14 days following surgery is recommended
to evaluate incision healing.
If bone marrow disease is present follow-up blood work
will need to be performed to monitor for improvement in red
blood cell, white blood cell, and platelet numbers.
Patients with malignant tumors should be re-evaluated
every three to four months for recurrence or metastasis.
Surgery is curative for most testicular tumors. About
10 to 20% of the cases have spread at the time of diagnosis.
Interstitial cell tumors and Sertoli cell tumors
without spread or damage to the cells of the bone marrow
have an excellent prognosis.
Seminomas without signs of hyperestrogenism also have
an excellent prognosis.
Damage to the cells of the bone marrow (caused by the
excessive estrogen levels) can be fatal despite therapy,
but usually improves two to three weeks after tumor
The prognosis for testicular tumors that have spread
is more guarded, but varies greatly depending on the
location, type of tumor, and treatment options.