Page 649 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

CHAPTER 29 Tumors of the Male Reproductive System 627

TABLE 29.1 Characteristics of the Three Most Common Testicular Tumors in the Dog
Biologic Behavior
VetBooks.ir Tumor Type Incidence (% of all Hormone Clinical Findings Gross and Potential for
Appearance
Metastasis
Production
testicular tumors) Origin
Sertoli Cell 8%–33% Sustentacular ≥50% Estrogen Feminization syndrome Firm <15% regional or
Tumor cells of Pancytopenia Lobulated distant metastasis
seminiferous White-gray
tubules “Greasy”
Interstitial 33%–50% Leydig cells Rarely estrogen Often incidental finding Soft Rarely metastasize
Cell Tumor between Testosterone Perianal gland hyperplasia/ Expansive
(Leydig Cell seminiferous adenomas Yellow-orange
Tumor) tubules Often cystic
Seminomas 33%–52% Germinal Rarely estrogen Often incidental finding Soft <15% regional or
epithelium of Metastasis may cause Homogeneous distant metastasis
seminiferous lethargy May be lobulated
tubules Ivory

• Fig. 29.1 Cross-sectional computed tomography image demonstrating an enlarged, minimally rim-
enhancing Sertoli cell tumor (blue arrow) in a dog with inguinal cryptorchidism. (Image courtesy Dr. T.
Schwarz, University of Edinburgh.)

Pathology and Pathogenesis
German shepherd dog, Afghan hound, Weimaraner, Shetland
sheepdog, collie, and Maltese. 3,8,14,25,32,34,35 Flat-coated retriev- Sertoli cell tumors arise from the sustentacular cells of seminifer-
ers, Rottweilers, Bouvier de Flandres, and Leonbergers may have a ous tubules and seminomas arise from the germinal epithelium
reduced risk of developing testicular tumors, although low num- of seminiferous tubules. Interstitial cell tumors arise from Leydig
bers of the latter two breeds were evaluated. 8 cells located between seminiferous tubules. All three tumors have
Two studies evaluating military working dogs suggested evi- relatively distinct appearances grossly, but require histopathology
dence of environmental carcinogen exposure during the Vietnam for definitive diagnosis. Sertoli cell tumors are firm, lobulated,
War as a contributor to testicular tumor development. 36,37 Patho- white-to-gray in appearance, and often characterized as “greasy”
38
logic changes in the testicles were noted, such as hemorrhage, on palpation. Seminomas tend to be homogeneous, soft, and
epididymitis, orchitis, sperm granuloma, testicular degeneration, occasionally lobulated with an ivory appearance when sectioned
38
and seminoma, although the causative factor of these lesions (Fig. 29.2). Interstitial cell tumors are soft, expansive, and yel-
could not be definitively determined. These epidemiologic stud- low-to-orange in color when sectioned and often contain cysts
ies postulated that exposure to phenoxy herbicide, dioxin, or with serous or serosanguineous fluid. 38
tetracycline may have promoted the development of testicular The molecular and cellular biology of primary testicular
tumors. 36,37 tumors has been investigated in recent years. Proliferation markers