History
A 10-year-old 9.4-kg (20.7-lb) neutered male Fox Terrier with atopic dermatitis (originally diagnosed at 16 months of age) triggered by environmental and food allergens underwent reevaluation. Since the time of the initial diagnosis, the dog regularly received immunotherapy injections,a shampoo therapy,b and ear cleaning with a topical ear cleanserc as well as a hypoallergenic prescription dietd to control pruritus. Three years prior, a diagnosis of inflammatory bowel disease had been made, which was also controlled and in remission through consumption of the hypoallergenic prescription diet.d At the time of reevaluation, the dog was being treated with prednisonee (0.5 mg/kg [0.23 mg/lb], PO, every other day) to manage a flare-up episode of atopic dermatitis. The dog's vaccination and deworming status was current.
Clinical and Clinicopathologic Findings
At the reevaluation, the dog was bright, alert, and responsive. Physical examination findings were unremarkable except for severe dental tartar and moderate gingivitis. Dermatologic examination revealed an approximately 1.5-cm-diameter, firm, multilobulated, dermal mass on the ventral aspect of the abdomen immediately cranial to the scrotum. According to the owner, the mass had been present for 2 to 3 years and had recently grown slightly in size. The remainder of the dermatologic examination findings were considered normal. A fine-needle aspirate sample of the mass was obtained for cytologic examination (Figure 1). On a pale gray, basophilic background, cohesive sheets and individualized round to polygonal and occasionally spindloid cells were observed. Some cells formed pseudoacinar structures. Occasionally, cells had very distinct cell borders, and moderate amounts of basophilic cytoplasm were occasionally filled with few small, discrete clear vacuoles. Round to slightly oval eccentric nuclei had finely to coarsely stippled chromatin and 1 to multiple prominent, occasionally large nucleoli. Few binucleated cells and moderate anisocytosis and mild anisokaryosis were present.
Photomicrograph of an aspirate sample from a 1.5 × 1.5-cm dermal mass located on the ventral aspect of the abdomen cranial to the scrotum on a 10-year-old dog undergoing reevaluation because of atopic dermatitis. Cohesive sheets and individualized round to polygonal to occasionally spindloid cells are observed. Some cells form pseudoacinar structures (asterisk). Occasionally, cells have very distinct cell borders. Cells had moderate amounts of basophilic cytoplasm occasionally filled with few small, discrete clear vacuoles (arrow). Round to slightly oval eccentric nuclei have finely to coarsely stippled chromatin and one to multiple prominent, occasionally large nucleoli. Few binucleated cells (arrowhead), moderate anisocytosis, and mild anisokaryosis are present. Wright-Giemsa stain; bar = 10 μm.
Citation: Journal of the American Veterinary Medical Association 249, 9; 10.2460/javma.249.9.1023
Photomicrograph of an aspirate sample from a 1.5 × 1.5-cm dermal mass located on the ventral aspect of the abdomen cranial to the scrotum on a 10-year-old dog undergoing reevaluation because of atopic dermatitis. Cohesive sheets and individualized round to polygonal to occasionally spindloid cells are observed. Some cells form pseudoacinar structures (asterisk). Occasionally, cells have very distinct cell borders. Cells had moderate amounts of basophilic cytoplasm occasionally filled with few small, discrete clear vacuoles (arrow). Round to slightly oval eccentric nuclei have finely to coarsely stippled chromatin and one to multiple prominent, occasionally large nucleoli. Few binucleated cells (arrowhead), moderate anisocytosis, and mild anisokaryosis are present. Wright-Giemsa stain; bar = 10 μm.
Citation: Journal of the American Veterinary Medical Association 249, 9; 10.2460/javma.249.9.1023
Photomicrograph of an aspirate sample from a 1.5 × 1.5-cm dermal mass located on the ventral aspect of the abdomen cranial to the scrotum on a 10-year-old dog undergoing reevaluation because of atopic dermatitis. Cohesive sheets and individualized round to polygonal to occasionally spindloid cells are observed. Some cells form pseudoacinar structures (asterisk). Occasionally, cells have very distinct cell borders. Cells had moderate amounts of basophilic cytoplasm occasionally filled with few small, discrete clear vacuoles (arrow). Round to slightly oval eccentric nuclei have finely to coarsely stippled chromatin and one to multiple prominent, occasionally large nucleoli. Few binucleated cells (arrowhead), moderate anisocytosis, and mild anisokaryosis are present. Wright-Giemsa stain; bar = 10 μm.
Citation: Journal of the American Veterinary Medical Association 249, 9; 10.2460/javma.249.9.1023
Formulate differential diagnoses from the history, clinical findings, and Figure 1—then turn the page→
Additional Histopathologic Findings
In the highly cellular fine-needle aspirate sample of the dermal mass, individualized cells had very distinct cell borders, but cell borders appeared more indistinct when cells were arranged in cohesive sheets. Rare acinus-like structures were noted. Low numbers of macrophages with abundant vacuolated cytoplasm were seen (not shown). Scattered nondegenerated neutrophils appeared in proportion to the degree of hemodilution. No etiologic agents were identified. Cytologic diagnosis was discrete cell neoplasia. Given the presence of vacuolated round to spindloid cells, possible considerations for the skin mass were perivascular wall tumor, peripheral nerve sheath tumor, or transmissible venereal tumor. In addition, the finding of bi- and multinucleated cells within a moderately pleomorphic cell population could also be associated with plasmacytoma, histiocytic sarcoma, or amelanotic melanoma. However, further differentiation could not be reliably done on the basis of cytologic findings; therefore, collection and histologic examination of a biopsy specimen was recommended for further characterization.
The following week, an excisional biopsy specimen was obtained by the referring veterinarian. Histologic examination of the specimen revealed a well-demarcated, multilobular, encapsulated neoplastic mass composed of Sertoli cells that was focally expanding the subcutis and elevating the overlying epidermis (Figures 2–4). Neoplastic cells were arranged in well-formed tubules, with the long axis of cells perpendicular to the tubular basement membrane, supported and separated by a moderately thick fibrous stroma. Neoplastic cells had indistinct cell borders and moderate to abundant amounts of pale eosinophilic to clear cytoplasm that streamed toward the center of the tubules. Nuclei were oval to elongate, typically in a basilar location, with a moderate amount of chromatin in a finely stippled pattern, containing 0 or 1 visible nucleolus. Anisocytosis and anisokaryosis were moderate. Mitotic figures were rare (mitotic rate, < 1 mitotic figure/10 hpfs [400X]). The specimen margins were free of tumor cells.
Photomicrograph of a haired skin (arrow) section of the prescrotal dermal mass in the dog in Figure 1 after surgical removal. Notice the focal expansion of the subcutis and elevation of the overlying epidermis by a well-demarcated, multilobular, encapsulated neoplastic mass (outlined by asterisks), which was composed of Sertoli cells. H&E stain; bar = 500 μm.
Citation: Journal of the American Veterinary Medical Association 249, 9; 10.2460/javma.249.9.1023
Photomicrograph of a haired skin (arrow) section of the prescrotal dermal mass in the dog in Figure 1 after surgical removal. Notice the focal expansion of the subcutis and elevation of the overlying epidermis by a well-demarcated, multilobular, encapsulated neoplastic mass (outlined by asterisks), which was composed of Sertoli cells. H&E stain; bar = 500 μm.
Citation: Journal of the American Veterinary Medical Association 249, 9; 10.2460/javma.249.9.1023
Photomicrograph of a haired skin (arrow) section of the prescrotal dermal mass in the dog in Figure 1 after surgical removal. Notice the focal expansion of the subcutis and elevation of the overlying epidermis by a well-demarcated, multilobular, encapsulated neoplastic mass (outlined by asterisks), which was composed of Sertoli cells. H&E stain; bar = 500 μm.
Citation: Journal of the American Veterinary Medical Association 249, 9; 10.2460/javma.249.9.1023
Photomicrograph (higher magnification) of the prescrotal dermal mass section in Figure 2. Neoplastic Sertoli cells are arranged in well-formed tubules (asterisks) with the long axis of cells perpendicular to the tubular basement membrane; these tubules are supported and separated by a moderately thick fibrous stroma (arrowheads). H&E stain; bar = 100 μm.
Citation: Journal of the American Veterinary Medical Association 249, 9; 10.2460/javma.249.9.1023
Photomicrograph (higher magnification) of the prescrotal dermal mass section in Figure 2. Neoplastic Sertoli cells are arranged in well-formed tubules (asterisks) with the long axis of cells perpendicular to the tubular basement membrane; these tubules are supported and separated by a moderately thick fibrous stroma (arrowheads). H&E stain; bar = 100 μm.
Citation: Journal of the American Veterinary Medical Association 249, 9; 10.2460/javma.249.9.1023
Photomicrograph (higher magnification) of the prescrotal dermal mass section in Figure 2. Neoplastic Sertoli cells are arranged in well-formed tubules (asterisks) with the long axis of cells perpendicular to the tubular basement membrane; these tubules are supported and separated by a moderately thick fibrous stroma (arrowheads). H&E stain; bar = 100 μm.
Citation: Journal of the American Veterinary Medical Association 249, 9; 10.2460/javma.249.9.1023
Photomicrograph (higher magnification) of the prescrotal dermal mass section in Figure 2. Neoplastic cells have indistinct cell borders and a moderate to abundant amount of pale eosinophilic to clear cytoplasm that streams toward the center of the tubules (asterisks); moderate anisocytosis and anisokaryosis are present. Nuclei (arrows) are oval to elongate, typically in a basilar location, with a moderate amount of chromatin in a finely stippled pattern and 0 or 1 visible nucleolus. H&E stain; bar = 20 μm.
Citation: Journal of the American Veterinary Medical Association 249, 9; 10.2460/javma.249.9.1023
Photomicrograph (higher magnification) of the prescrotal dermal mass section in Figure 2. Neoplastic cells have indistinct cell borders and a moderate to abundant amount of pale eosinophilic to clear cytoplasm that streams toward the center of the tubules (asterisks); moderate anisocytosis and anisokaryosis are present. Nuclei (arrows) are oval to elongate, typically in a basilar location, with a moderate amount of chromatin in a finely stippled pattern and 0 or 1 visible nucleolus. H&E stain; bar = 20 μm.
Citation: Journal of the American Veterinary Medical Association 249, 9; 10.2460/javma.249.9.1023
Photomicrograph (higher magnification) of the prescrotal dermal mass section in Figure 2. Neoplastic cells have indistinct cell borders and a moderate to abundant amount of pale eosinophilic to clear cytoplasm that streams toward the center of the tubules (asterisks); moderate anisocytosis and anisokaryosis are present. Nuclei (arrows) are oval to elongate, typically in a basilar location, with a moderate amount of chromatin in a finely stippled pattern and 0 or 1 visible nucleolus. H&E stain; bar = 20 μm.
Citation: Journal of the American Veterinary Medical Association 249, 9; 10.2460/javma.249.9.1023
Morphologic Diagnosis and Case Summary
Morphologic diagnosis and case summary: extratesticular cutaneous Sertoli cell tumor in a dog.
Comments
In the dog of the present report, the prescrotal dermal mass was diagnosed as an extratesticular Sertoli cell tumor. Findings of the cytologic examination of a fine-needle aspirate sample from the mass were diagnostic for neoplasia, but not for the specific type of neoplasia. Retrospectively, cells observed from the cutaneous mass aspirate sample had some features that overlapped with those described for canine testicular Sertoli cell tumors,1 but given the location of the lesion in this dog and the fact that the dog was neutered, testicular origin of the neoplasm was not included among the initial differential diagnoses. However, histologic examination of sections of the mass revealed a very distinct and characteristic morphology of Sertoli cells and provided a definitive diagnosis of a dermal extratesticular Sertoli cell tumor.
Tumors of primary testicular tissue origin at extratesticular locations are extremely rare in dogs. To the authors' knowledge, only a single case2 and a case series of 12 dogs3 have been reported. Similar to the case described in the present report, all previous reports involved adult neutered males.2–4 Interestingly, there is typically an extended interval between castration and tumor detection. For the dog of the present report, castration was performed within the first year after birth and both testes were removed without complication; at 10 years of age, an extratesticular Sertoli cell tumor was diagnosed. Similarly, the mean time between castration and extratesticular tumor identification in dogs was 8 years in another report.3 In this dog, the tumor was located in the prescrotal skin. The prescrotal skin, scrotal skin, and spermatic cord are the most commonly reported locations for extratesticular testicular tumors.2–4 Rarely, these tumors develop at the castration incision site.3 Similar to the case described in the present report, most canine extratesticular tumors are Sertoli cell tumors; extratesticular interstitial cell tumors are far less common3,4 and, to the authors' knowledge, extratesticular seminomas have not been reported.
Although not applicable to the dog of the present report, dogs with extratesticular Sertoli cell tumors may have signs of hyperestrogenism, such as bilateral symmetric alopecia and feminization, including pendulous prepuce, gynecomastia, and attraction of male dogs.2,3 Similar to its testicular counterpart, secondary sexual characteristics are reversible following surgical removal of the extratesticular Sertoli cell tumor.2,3 The reported biologic behavior of extratesticular testicular neoplasms appears to be benign; in the dog of the present report, the skin mass had been present for at least 2 years without causing clinical signs before removal and diagnosis. Six months following surgical removal, no evidence of tumor recurrence was detected. Likewise, tumor metastases or deaths attributable to these extratesticular neoplasms have not been reported.2–4
The pathogenesis of extratesticular Sertoli cell tumors remains unclear. As many as 58 of 108 (53.7%) testicular Sertoli cell tumors in dogs develop in undescended testes,5,6 and although the metastatic rate of primary testicular Sertoli cell tumors is < 15%,7,8 metastases have been detected up to 8 years following surgical removal of the primary testicular tumor.9,10 Thus, extratesticular cutaneous metastasis from an undescended testis or a previously removed testicular Sertoli cell tumor should also be considered. In the case described in the present report, the extratesticular tumor was most likely a primary tumor rather than a metastatic lesion for multiple reasons. First, there was no evidence of either an undescended testis at the time of tumor diagnosis or a primary testicular tumor at time of castration. Second, all reported extratesticular Sertoli cell tumors and extratesticular Leydig cell tumors in a similar location in dogs were suspected to be primary tumors given the lack of evidence of other neoplasia at both the time of castration and tumor diagnosis.7 Third, reported sites of Sertoli cell tumor metastases include abdominal lymph nodes, kidneys, liver, spleen, pancreas, mediastinum, and lungs,7–12 and to the authors' knowledge, skin metastases associated with Sertoli cell tumors have not been reported. Finally, it is unusual to have disseminated metastatic disease including metastasis to the skin without any systemic clinical signs. Other possible considerations for origin of these neoplasms include ectopic remnant embryological testicular tissue and transplantation of testicular tissue during castration or prior testicular trauma with eventual neoplastic transformation of transplanted cells.3
Despite the fact that these neoplasms are rare, an extratesticular Sertoli cell tumor must be considered as a potential differential diagnosis on the basis of the results of clinical, cytologic, and histopathologic evaluations of an extratesticular nodule or mass in the scrotal area of a neutered male dog. Histologic examination of mass tissue is crucial for definitive diagnosis.
Acknowledgments
The authors thank Dr. Frane Banovic for technical assistance.
Footnotes
Greer Laboratories Inc, Lenoir, NC.
Vétoquinol USA Inc, Fort Worth, Tex.
Virbac AH Inc, Fort Worth, Tex.
Nestle Purina PetCare, St Louis, Mo.
Roxane Laboratories, Columbus, Ohio.
References
1. Masserdotti C, Bonfanti U, De Lorenzi D, et al. Cytologic features of testicular tumours in dog. J Vet Med A Physiol Pathol Clin Med 2005; 52: 339–346.
2. Robinson RR. A Sertoli cell tumor in ectopic testicular tissue. Mod Vet Pract 1973; 54: 69.
3. Doxsee AL, Yager JA, Best SJ, et al. Extratesticular interstitial and Sertoli cell tumors in previously neutered dogs and cats: a report of 17 cases. Can Vet J 2006; 47: 763–766.
4. Rosen DK, Carpenter JL. Functional ectopic interstitial cell tumor in a castrated male cat. J Am Vet Med Assoc 1993; 202: 1865–1866.
5. Reif JS, Brodey RS. The relationship between cryptorchidism and canine testicular neoplasia. J Am Vet Med Assoc 1969; 155: 2005–2010.
6. Liao AT, Chu PY, Yeh LS, et al. A 12-year retrospective study of canine testicular tumors. J Vet Med Sci 2009; 71: 919–923.
7. Brodey RS, Martin JE. Sertoli cell neoplasms in the dog: the clinicopathological and endocrinological findings in thirty-seven dogs. J Am Vet Med Assoc 1958; 133: 249–257.
8. Weaver AD. Survey with follow-up of 67 dogs with testicular Sertoli cell tumours. Vet Rec 1983; 113: 105–107.
9. Dhaliwal RS, Kitchell BE, Knight BL, et al. Treatment of aggressive testicular tumors in four dogs. J Am Anim Hosp Assoc 1999; 35: 311–318.
10. Gopinath D, Draffan D, Philbey AW, et al. Use of intralesional oestradiol concentration to identify a functional pulmonary metastasis of canine Sertoli cell tumour. J Small Anim Pract 2009; 50: 198–200.
11. Coffin DL, Munson TO, Scully RE. Functional Sertoli cell tumor with metastasis in a dog. J Am Vet Med Assoc 1952; 121: 352–359.
12. Lipowitz AJ, Schwartz A, Wilson GP, et al. Testicular neoplasms and concomitant clinical changes in the dog. J Am Vet Med Assoc 1973; 163: 1364–1368.
