+ 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

+ Seminoma

  • Seminomas arise from germinal epithelium and are usually solitary masses
  • Seminomas are bilateral in 18% dogs
  • 34% of seminomas are found in cryptorchid testicles
  • 16-times risk of developing seminoma in the cryptorchid testicle compared to descended testicle in dogs with unilateral cryptorchidism
  • Seminoma in descended testicle found in younger dogs and associated with contralateral cryptorchid testicle
  • Seminomas are associated with prostatic disease and enlargement, circumanal gland hyperplasia, and perianal tumors ± perineal hernia
  • < 10% metastatic rate
  • Metastatic sites including sublumbar lymph node (common), lungs, liver, spleen, adrenal glands, pancreas, CNS, eyes, and skin
  • AgNOR counts are higher in dogs with metastatic seminoma compared to non-metastatic seminoma

+ Other Testicular Tumors

  • Other tumors include hemangioma, granulosa cell tumor, sarcoma, embryonal carcinoma, gonadoblastoma, and LSA
  • Testicular teratoma is very rare in dogs
  • Metastatic testicular tumors from GI ADC have been reported in 3 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
  • 137cesium external beam radiation therapy has been used in 4 dogs with metastatic seminoma with CR in 3 dogs and no evidence of recurrence
  • Platinum-based chemotherapy protocols are recommended in humans and dogs with metastatic seminoma
  • Bleomycin used successfully in 1 dog with cutaneous metastasis with no recurrence by 12 months
  • Vincristine and cyclophosphamide were not effective in 1 dog with cutaneous metastasis

+ Prognosis

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