+ 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

+ Interstitial Cell Tumor

  • Interstitial or Leydig cells are found in the fibrovascular stroma of the testicle and produce testosterone
  • Interstitial cell tumors are the most common testicular tumor in dogs
  • Interstitial cell tumors are benign but functional tumors and associated with prostatic disease and enlargement, circumanal gland hyperplasia, and perianal tumors ± perineal hernia
  • Interstitial cell tumors are bilateral in 43% dogs


+ Clinical Signs

  • 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 is rare in dogs with interstitial cell tumors

+ 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

+ Prognosis

Castration is curative if no bone marrow hypoplasia, myelosuppression, or metastatic disease