+ 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
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 FEATURES
+ 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