A Sertoli cell tumor is a tumor in the testicles that involves the specific cells called Sertoli cells. Sertoli cell tumors are usually slow growing and noninvasive, although 10 to 20 percent may be malignant.

The specific cause of tumor development is unknown, but dogs that are cryptorchid, which means they have a testicle that has not descended into the scrotum, are 10 times more likely to develop a tumor. Cryptorchid testicles are generally intra-abdominal (within the abdomen), but may be under the skin in the inguinal area, or the area of the body where the hind leg meets the body wall.

Breeds at greater risk of cryptorchidism like Weimaraners and Shetland sheepdogs are more likely to develop a Sertoli cell tumor. Boxers are at increased risk of all testicular tumors regardless of cryptorchidism. Dogs are more likely to develop a Sertoli cell tumor with age.

Sertoli cell tumors are the most common tumors that cause a male feminizing syndrome due to changes in sex hormone production. About 25 percent of dogs with this tumor develop the male feminizing syndrome. Sertoli cell tumors can also cause a severe bone marrow disorder (bone marrow hypoplasia).

Most dogs that present with Sertoli cell tumors are not ill, and many are simply found during a routine physical examination.

What to Watch For

Soft or firm swellings in one or both testicles

A single enlarged testicle or asymmetric testicles

Generalized scrotal enlargement

Infertility in the breeding stud dog

If male feminization is present:

Enlargement of the mammary glands

A symmetrical hair loss

Hyperpigmentation, which causes the skin to darken or turn black

Decreased libido and a pendulous prepuce

Diagnosis

A good physical examination including palpation (feeling) of the testicles

Complete blood count (CBC)

Platelet count

Biochemical profile

Urinalysis with or without culture and sensitivity

Thoracic (chest) and abdominal radiographs (x-rays)

Abdominal and or scrotal ultrasound

Plasma estrogen levels

Preputial swabs

Serum inhibin concentrations

Fine needle aspiration

Biopsy and histopathology (microscopic analysis of tissue) of removed testicle or tumor

Treatment

Surgical removal of the involved testes (orchiectomy)

Chemotherapy if the tumor has metastasized

Supportive care if associated disease conditions are present

Home Care and Prevention

Watch the incision daily for any sign of swelling or discharge. The scrotal sack may be slightly swollen postoperatively, but the swelling should slowly resolve within a week or two.

If skin sutures are used, they should be removed in 7 to 10 days. If your dog begins to lick the area excessively, an Elizabethan collar may be required.

Seek veterinary care if your dog has a fever or feels ill postoperatively. If your dog had bone marrow hypoplasia due to a Sertoli cell tumor, close monitoring of blood tests will be required.

An excellent preventive measure is to have your dog neutered (castrated) at an early age.