+ General Considerations

  • Testicular tumors are common and account for 4%-7% of all tumors in male dogs
  • Testicular tumors broadly classified into 2 groups based on histology:
  • Group I: germ cell tumors such as seminoma, embryonal carcinoma, and teratoma
  • Group II: Sertoli cell tumor, interstitial cell tumor, and mixed testicular tumors
  • Mixed testicular tumors may be classified separately
  • Mixed germ cell-stromal tumors have a dual population of germ and Sertoli cells and account for 7% of canine testicular tumors
  • Breed predisposition: Siberian Husky, Norwegian Elkhound, Fox Terrier, Afghan Hound, and Shetland Sheepdog
  • Dachshund, Rottweiler, Shih Tzu, Yorkshire Terrier, Toy Poodle, Miniature Schnauzer, and mixed breed dogs have a significantly decreased risk of developing testicular tumors

alt text From: Withrow SJ & MacEwen EG (eds): Small Animal Clinical Oncology (3rd ed).

  • 50% of dogs over 10 years have multiple tumors of different histologic types
  • Testicular tumors are uncommon in dogs < 6 years
  • Sertoli cell tumor and seminoma are more common with cryptorchid testicles

+ Sertoli Cell Tumor

  • Sertoli cells produce estrogen, support germ cells, and form seminiferous tubule basement membrane
  • Sertoli cell tumors tend to grow in expansile fashion that compress and destroy surrounding parenchyma
  • Sertoli cell tumors are bilateral in 11% dogs
  • 54% of Sertoli cell tumors are found in cryptorchid testicles
  • 8.8-times risk of developing a Sertoli cell tumor in the cryptorchid testicle compared to descended testicle in dogs with unilateral cryptorchidism
  • Testicular microenvironment influences the development of testicular tumors as, in humans, early surgical correction of cryptorchidism (i.e., orchipexy) decreases risk of testicular neoplasia
  • Sertoli cell tumor in descended testicle found in younger dogs and associated with contralateral cryptorchid testicle
  • Sertoli cell tumors are associated with a decreased risk of prostatic disease, circumanal gland hyperplasia, perianal tumors, and perineal hernia
  • 0.6%-9.0% metastatic rate with metastatic sites including sublumbar lymph node (common), lungs, liver, spleen, adrenal glands, kidney, and pancreas


Clinical Signs

+ General Considerations

  • Incidental finding at surgery or necropsy
  • Scrotal or inguinal mass or enlargement
  • Hypertrophic osteopathy reported in 1 dog with metastatic Sertoli cell tumor to lungs and kidney

+ Feminization Syndrome

  • Feminization is rare in dogs with interstitial cell tumors and seminomas, but can occur with Sertoli cell tumors
  • Feminization dependent on testicular location with feminization occurring in 16% of scrotal testes, 50% of inguinal testes, and 70% of intra-abdominal testes
  • Hyperestrogenism has been implicated in the pathogenesis of feminization but this has not been proven
  • Clinical signs of feminization include:
  • Bone marrow hypoplasia with thrombocytopenia, hemorrhage, anemia and granulocytopenia
  • Symmetrical and squamous metaplasia of the prostate resulting in cystic benign prostatic hyperplasia
  • Gynecomastia and galactorrhea
  • Attractiveness to other males
  • Atrophy of non-neoplastic testicle due to negative feedback of estrogen on the pituitary-hypothalamus axis
  • Penile atrophy with pendulous prepuce
  • Bilaterally symmetrical alopecia in the genital area, inner thighs, abdomen, chest, shoulders, and thighs
  • 69% mortality rate

+ Diagnosis

  • Scrotal palpation
  • Rectal examination, lateral abdominal radiograph, abdominal ultrasonography, or direct examination during exploratory celiotomy to assess ± biopsy the sublumbar lymph nodes
  • Ultrasound examination is a sensitive and relatively specific technique for the diagnosis of testicular tumors with:
  • Interstitial cell tumors appearing as a well-circumscribed mass with predominantly hypoechoic and small hyperechoic areas
  • Sertoli cell tumors disrupting internal architecture with echogenic pattern varying from anechoic to mixed echogenicity
  • Aspiration or biopsy are invasive, compromise testicular-blood barrier and may predispose to infertility and spermatic granuloma formation
  • ± thoracic radiographs
  • Histopathology following castration

+ Treatment

  • Castration with resection of a large amount of the spermatic cord
  • Fresh whole blood transfusion for dogs with Sertoli cell tumors if myelosuppressed with thrombocytopenia and anemia

+ Prognosis

  • Castration is curative if no bone marrow hypoplasia, myelosuppression, or metastatic disease
  • Mortality > 80% if severe myelosuppression
  • Hematologic parameters usually improve within 2-4 weeks but can take up to 5 months to return to normal