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Testicular teratoma in a stallion
CASE REPORT
Ji
'~
\j
Refereed
TESTICULAR TERATOMAIN A STALLION D. J. Jasko, DVM, MS, PhD; 1 B. E. Powers, DVM, PhD; ~ G. W. Trotter, DVM, MS; 1 E. L. Squires, PhD 2
SUMMARY A 4-year-old Arabian stallion was presented for a routine fertility evaluation. Seminal characteristics of ejaculates collected from the stallion were similar to those of other fertile stallions; however, a mass (2.5 cm 3) was palpable within the cranial portion of the left testicle. At castration a presumptive diagnosis of testicular teratoma was made and later confirmed by histopathological examination.
INTRODUCTION Testicular masses in stallions may lead to subfertility or infertility due to either compression or replacement of normal testicular tissue or from the blockage of sperm transport to the excurrent ducts. A differential diagnosis of testicular mass or testicular enlargement would include neoplasia, testicular torsion, orchitis, testicular abscessation, sperm granuloma, and testicular hematoma. 1,2These diseases are uncommon in the stallion?"3 Ultrasonographic evaluation of a testicle containing a mass may be useful in making a presumptive diagnosis? Testicular biopsy can also be used to make a presumptive diagnosis of a testicular mass. Testicular biopsy has been advocated for the diagnosis of testicular neoplasia,2 however there is risk of testicular hemorrhage following biopsy.~ Testicular neoplasms in the stallion are uncommonz3 and are classified according to the cell type from which the tumor Authors' addresses: 1Departments of Clinical Sciences and 2Physiology, Cortege of Veterinary Medicine and Biomedical Sciences, Cotorado State University, Fort Collins, CO 80523. Accepted for publication: 5 January 1991.
108
arises. Those tumors arising from germ or spermatogenic cell types includeseminomas and teratomas.InterstitialorLeydig cell tumors originate from the interstitial tissue, while Sertoli cell tumors arise from the nonspermatogenic cells of the seminiferous tubules. Teratomas have been reported in both descended and cryptorchid stallion testicles, although the incidence is thought to be higher in cryptorchid testicles.2'6~ The incidence of this type of tumor seems to be less than that for seminomas, which has the highest incidence of the testicular tumors reported in the stallion? Teratomas contain tissue derived from one or more of the three germ layers (ectoderm, mesoderm, and endoderm) and often include nervous tissue, keratinized stratified squamous epithelium, and cartilage or bone. These tumors are usually benign, multicentric, and often detected in younger stallions? The effect of testicular teratomas on spermatogenesis is probably from a displacement and compression of normal tissue.
CASE HISTORY A 4-year-old Arabian stallion was presented for an evaluation of potential fertility in May, 1990. This stallion was not used for breeding in prior years and was mated with only a few mares during the 1990 breeding season using natural service. Two of three mated mares were thought to have not become pregnant due to a continuance of the normal cyclicity of estrus in these mares. One of these mares was reported as being an older mare with past breeding difficulties. An examination for potential fertility was performed as outlined by the Society for Theriogenology.l° Semen was collected with a Colorado model artificial vagina containing an in-line gel filter. Upon dismounting, swabs for bacterial
EQUINE VETERINARY SCIENCE
Table 1. Seminal characteristics for the first and second ejaculates obtained from a stallion with a testicular teratoma. Seminal characteristic
Gel-free volume (ml) Sperm cell concentration (10"/ml) Subjective appraisal of progressive motility (%) Total sperm per ejaculate (10") Seminal pH Morphologically normal sperm (%)
Ejaculate First Second 47 683
40 165
65 32 6.99 76
70 7 7.33 69
culture were obtained from the urethra and prepuce. An additional culture swab was obtained direcdy from the semen. A second collection was obtained approximately one hour after the first. Seminal characteristics of both ejaculates (Table 1) were considered to be similar to those of other normal stallions. 11 However, there was greater than a 50% reduction in the number of sperm cells obtained in the second ejaculate as compared with the first (32 vs 7 billion, respectively) indicating that either one of the ejaculates may not have been representative of the stallion's current sperm production.12 The large number of sperm cells in the first ejaculate may have been from the accumulation of sperm due to the stallion being sexually rested prior to the examination. Sperm morphological features (Table 1) were also consistent with those of normal stallions? ~,13 In addition no potentially pathogenic bacteria were isolated from any of the six swabs obtained during the fertility evaluation. Upon palpation of the stallion's scrotum, two testicles were evident with a total scrotal width of 10.5 cm. It was thought that both testicles had normal consistency; however, a mass (2.5 cm3) was detected in the anterior aspect of the left testicle in the area where the efferent tubules leave the testicle to form the head of the epididymis. This stallion was classified as a questionable potential breeder due to the palpable lesion in the left testicle. However, based on the seminal characteristics noted for both semen collections, it was presumed that this stallion was fertile at the time of presentation. A prognosis for the future fertility of this stallion was not given as the owner elected not to attempt to obtain a diagnosis of the mass. Unilateral castration was not recommended at that time due to the presumed limited affect this lesion was having on spermatogenesis based on the recorded seminal characteristics. It was recommended that the stallion's seminal characteristics and testicular consistency to be monitored frequendy. The stallion returned to the breeding farm, however approximately one month later the stallion was re-presented for an elective castration. The stallion was anesthetized using intravenous anesthesia and a standard open castration performed.
Volume 11, Number 2, 1991
Figure 1. Sagittal section through the left testis of a stallion with a testicular teratoma. Adjacent to the head of the epididymis is a cystic cavity containing keratin debris and hair. A second serous cavity is below the hair-filled cavity. A pale, smaller, solid mass is located centrally in the testicle.
PATHOLOGICAL FINDINGS
Following castration, the intact testicles appeared grossly normal, however, a palpable mass was again detected in the parenchyma of the left testicle near the formation of the head of the epididymis. Serial cuts were made through both testicles. No abnormalities were noted in the right testicle. Upon sectioning of the left testicle, multiple abnormal masses (cysts) were detected. A 3 cm 3 spherical cavity (Fig. 1) filled with keratinized debris and fine, short hairs was found within the testicular parenchyma adjacent to the head of the epididymis. Below this cavity was a second, smaller serous fluid filled cavity (Fig. 1). A third smaller, pale solid mass (1 cm 3) was located centrally (Fig. 1) within the testicle. A presumptive diagnosis of testicular teratoma was made and sections of the left testicle were submitted for histological examination. On histological evaluation, testicular tissue surrounding the large cystic structures consisted of seminiferous tubules with a minimal production of spermatids. Connective tissue of dense collagen (2 mm thick) separated these tubules from the cystic structures (Fig. 2). One of the cysts was lined with stratified squamous epithelium with melanin pigment in the basal layer and was filled with keratinized debris. Deep to the cyst were well formed sebaceous glands, apocrine sweat glands, smooth muscle, vessels, nerves and a few hair follicles. The second cyst adjacent to this large, hair-filled cyst had a clear center and a wall composed of fibrillar, eosinophilic nerve-like tissue covered by a single layer of cuboidal epithelial cells. The separate, smaller, well demarcated, solid
109
Figure 3 . Histological section of a solid teratoma in a stallion testicle composed of nervous and adipose tissue. H & E stain.
logical appearance benign. In addition the tumor in this stallion contained tissue from at least two germ layers. Nervous tissue and keratinized stratified squamous epithelium are derived from ectoderm while adipose tissue is derived from mesoderm. No bone or cartilage was found contained within this tumor. The limited size of this tumor at the time of diagnosis precluded it from having a large affect on sperm production.
REFERENCES Figu re 2 . Histological section of the cystic cavity in a stallion testicle showing a keratinized stratified sq uamous epithelium. Deep to the cyst wall are sebaceous and sweat glands, smooth muscle, and nerves. H & E stain.
mass was composed of nervous and adipose tissue (Fig. 3). The nervous tissue consisted of bundles of fibrillar material with numerous astrocytes and occasional clusters of neurons surrounded by satellite cells. The adipose tissue was admixed with nervous tissue and consisted of normal appearing adipocytes. The unaffected testicular tissue appeared normal. A histological diagnosis of testicular teratoma was made.
DISCUSSION
The owner of this stallion elected not to have a biopsy performed at the time the testicular mass was initially identified, but rather to monitor the progression of the mass. Unilateral castration was not recommended at that time due to the limited evidence that spermatogenesis was being affected (Table 1). The re-presentation of the stallion for castration allowed a definite diagnosis to be made. The testicular teratoma diagnosed in this stallion is similar to other reported cases6-9 in that it was detected in a young stallion, found to be multicentric, and based on histo110
1. Neely DP: Physical examination and genital diseases of the stallion. In: Morrow DA (ed) Current Therapyin Theriogenology. Philadelphia, PA:WB Saunders Company, pp.694-706,1980. 2. Caron JP, BarberSM, Bailey JV: Equine testicular neoplas ia. Compend Contin Educ Pract Vet 7:$53-$59,1985. 3. Jubb KVF, Kennedy PC: Pathology of Domestic Animals. 2nd ed. New York, NY: Academic Press, pp.456-460,1970. 4. Held JP, Adair S, McGavin MD, et al: Bacterial epididymitis in two stallions. J Am Vet Med Assoc 197:602-604,1990. 5. Walker DF, Vaughan JT. Bovine and Equine Urogenital Surgery. Philadelphia, PA:Lea and Febiger, p. 165,1980. 6. Rebar A, Fessler JF, Erb R: Testicular teratoma in a horse: a case report and endrocrinologic study. J Equine Med Surg 3:361366,1979. 7. Stick JA: Teratoma and cyst formation of the equine cryptorchid testicle. J Am Association Vet Med 176:211-214,1980. 8. Conway DA: A teratoma in the undescended testicle in a horse. Irish Vet J 20:226-228,1966. 9. Symth GB: Testicular teratoma in an equine cryptorchid. Equine Vet J 11:21-23,1979. 10. Kenney RM, Hurtgen J, Pierson R, et al: Manual for breeding soundness examination of stallions. J Soc Therio 9:354,1983. 11. Pickett BW, Voss JL, Bowen RA, et al: Seminal characteristics and total scrotal width (TSW) of normal and abnormal stallions. In Proceedings. Am Assoc Equine Pract 33:487-518,1987. 12. Pickett BW, Voss JL: Reproductive management of the stallion. In Proceedings. Am Assoc Equine Pract 18:501-531,1972. 13. Jasko DJ, Lein DL, Foote RH: Determination of the relationship between sperm morphologic classifications and fertility in stallions: 66 cases (1987-1988). J Am Vet Med Assoc 197:389394,1990.
EQUINE VETERINARY SCIENCE
Ji
'~
\j
Refereed
TESTICULAR TERATOMAIN A STALLION D. J. Jasko, DVM, MS, PhD; 1 B. E. Powers, DVM, PhD; ~ G. W. Trotter, DVM, MS; 1 E. L. Squires, PhD 2
SUMMARY A 4-year-old Arabian stallion was presented for a routine fertility evaluation. Seminal characteristics of ejaculates collected from the stallion were similar to those of other fertile stallions; however, a mass (2.5 cm 3) was palpable within the cranial portion of the left testicle. At castration a presumptive diagnosis of testicular teratoma was made and later confirmed by histopathological examination.
INTRODUCTION Testicular masses in stallions may lead to subfertility or infertility due to either compression or replacement of normal testicular tissue or from the blockage of sperm transport to the excurrent ducts. A differential diagnosis of testicular mass or testicular enlargement would include neoplasia, testicular torsion, orchitis, testicular abscessation, sperm granuloma, and testicular hematoma. 1,2These diseases are uncommon in the stallion?"3 Ultrasonographic evaluation of a testicle containing a mass may be useful in making a presumptive diagnosis? Testicular biopsy can also be used to make a presumptive diagnosis of a testicular mass. Testicular biopsy has been advocated for the diagnosis of testicular neoplasia,2 however there is risk of testicular hemorrhage following biopsy.~ Testicular neoplasms in the stallion are uncommonz3 and are classified according to the cell type from which the tumor Authors' addresses: 1Departments of Clinical Sciences and 2Physiology, Cortege of Veterinary Medicine and Biomedical Sciences, Cotorado State University, Fort Collins, CO 80523. Accepted for publication: 5 January 1991.
108
arises. Those tumors arising from germ or spermatogenic cell types includeseminomas and teratomas.InterstitialorLeydig cell tumors originate from the interstitial tissue, while Sertoli cell tumors arise from the nonspermatogenic cells of the seminiferous tubules. Teratomas have been reported in both descended and cryptorchid stallion testicles, although the incidence is thought to be higher in cryptorchid testicles.2'6~ The incidence of this type of tumor seems to be less than that for seminomas, which has the highest incidence of the testicular tumors reported in the stallion? Teratomas contain tissue derived from one or more of the three germ layers (ectoderm, mesoderm, and endoderm) and often include nervous tissue, keratinized stratified squamous epithelium, and cartilage or bone. These tumors are usually benign, multicentric, and often detected in younger stallions? The effect of testicular teratomas on spermatogenesis is probably from a displacement and compression of normal tissue.
CASE HISTORY A 4-year-old Arabian stallion was presented for an evaluation of potential fertility in May, 1990. This stallion was not used for breeding in prior years and was mated with only a few mares during the 1990 breeding season using natural service. Two of three mated mares were thought to have not become pregnant due to a continuance of the normal cyclicity of estrus in these mares. One of these mares was reported as being an older mare with past breeding difficulties. An examination for potential fertility was performed as outlined by the Society for Theriogenology.l° Semen was collected with a Colorado model artificial vagina containing an in-line gel filter. Upon dismounting, swabs for bacterial
EQUINE VETERINARY SCIENCE
Table 1. Seminal characteristics for the first and second ejaculates obtained from a stallion with a testicular teratoma. Seminal characteristic
Gel-free volume (ml) Sperm cell concentration (10"/ml) Subjective appraisal of progressive motility (%) Total sperm per ejaculate (10") Seminal pH Morphologically normal sperm (%)
Ejaculate First Second 47 683
40 165
65 32 6.99 76
70 7 7.33 69
culture were obtained from the urethra and prepuce. An additional culture swab was obtained direcdy from the semen. A second collection was obtained approximately one hour after the first. Seminal characteristics of both ejaculates (Table 1) were considered to be similar to those of other normal stallions. 11 However, there was greater than a 50% reduction in the number of sperm cells obtained in the second ejaculate as compared with the first (32 vs 7 billion, respectively) indicating that either one of the ejaculates may not have been representative of the stallion's current sperm production.12 The large number of sperm cells in the first ejaculate may have been from the accumulation of sperm due to the stallion being sexually rested prior to the examination. Sperm morphological features (Table 1) were also consistent with those of normal stallions? ~,13 In addition no potentially pathogenic bacteria were isolated from any of the six swabs obtained during the fertility evaluation. Upon palpation of the stallion's scrotum, two testicles were evident with a total scrotal width of 10.5 cm. It was thought that both testicles had normal consistency; however, a mass (2.5 cm3) was detected in the anterior aspect of the left testicle in the area where the efferent tubules leave the testicle to form the head of the epididymis. This stallion was classified as a questionable potential breeder due to the palpable lesion in the left testicle. However, based on the seminal characteristics noted for both semen collections, it was presumed that this stallion was fertile at the time of presentation. A prognosis for the future fertility of this stallion was not given as the owner elected not to attempt to obtain a diagnosis of the mass. Unilateral castration was not recommended at that time due to the presumed limited affect this lesion was having on spermatogenesis based on the recorded seminal characteristics. It was recommended that the stallion's seminal characteristics and testicular consistency to be monitored frequendy. The stallion returned to the breeding farm, however approximately one month later the stallion was re-presented for an elective castration. The stallion was anesthetized using intravenous anesthesia and a standard open castration performed.
Volume 11, Number 2, 1991
Figure 1. Sagittal section through the left testis of a stallion with a testicular teratoma. Adjacent to the head of the epididymis is a cystic cavity containing keratin debris and hair. A second serous cavity is below the hair-filled cavity. A pale, smaller, solid mass is located centrally in the testicle.
PATHOLOGICAL FINDINGS
Following castration, the intact testicles appeared grossly normal, however, a palpable mass was again detected in the parenchyma of the left testicle near the formation of the head of the epididymis. Serial cuts were made through both testicles. No abnormalities were noted in the right testicle. Upon sectioning of the left testicle, multiple abnormal masses (cysts) were detected. A 3 cm 3 spherical cavity (Fig. 1) filled with keratinized debris and fine, short hairs was found within the testicular parenchyma adjacent to the head of the epididymis. Below this cavity was a second, smaller serous fluid filled cavity (Fig. 1). A third smaller, pale solid mass (1 cm 3) was located centrally (Fig. 1) within the testicle. A presumptive diagnosis of testicular teratoma was made and sections of the left testicle were submitted for histological examination. On histological evaluation, testicular tissue surrounding the large cystic structures consisted of seminiferous tubules with a minimal production of spermatids. Connective tissue of dense collagen (2 mm thick) separated these tubules from the cystic structures (Fig. 2). One of the cysts was lined with stratified squamous epithelium with melanin pigment in the basal layer and was filled with keratinized debris. Deep to the cyst were well formed sebaceous glands, apocrine sweat glands, smooth muscle, vessels, nerves and a few hair follicles. The second cyst adjacent to this large, hair-filled cyst had a clear center and a wall composed of fibrillar, eosinophilic nerve-like tissue covered by a single layer of cuboidal epithelial cells. The separate, smaller, well demarcated, solid
109
Figure 3 . Histological section of a solid teratoma in a stallion testicle composed of nervous and adipose tissue. H & E stain.
logical appearance benign. In addition the tumor in this stallion contained tissue from at least two germ layers. Nervous tissue and keratinized stratified squamous epithelium are derived from ectoderm while adipose tissue is derived from mesoderm. No bone or cartilage was found contained within this tumor. The limited size of this tumor at the time of diagnosis precluded it from having a large affect on sperm production.
REFERENCES Figu re 2 . Histological section of the cystic cavity in a stallion testicle showing a keratinized stratified sq uamous epithelium. Deep to the cyst wall are sebaceous and sweat glands, smooth muscle, and nerves. H & E stain.
mass was composed of nervous and adipose tissue (Fig. 3). The nervous tissue consisted of bundles of fibrillar material with numerous astrocytes and occasional clusters of neurons surrounded by satellite cells. The adipose tissue was admixed with nervous tissue and consisted of normal appearing adipocytes. The unaffected testicular tissue appeared normal. A histological diagnosis of testicular teratoma was made.
DISCUSSION
The owner of this stallion elected not to have a biopsy performed at the time the testicular mass was initially identified, but rather to monitor the progression of the mass. Unilateral castration was not recommended at that time due to the limited evidence that spermatogenesis was being affected (Table 1). The re-presentation of the stallion for castration allowed a definite diagnosis to be made. The testicular teratoma diagnosed in this stallion is similar to other reported cases6-9 in that it was detected in a young stallion, found to be multicentric, and based on histo110
1. Neely DP: Physical examination and genital diseases of the stallion. In: Morrow DA (ed) Current Therapyin Theriogenology. Philadelphia, PA:WB Saunders Company, pp.694-706,1980. 2. Caron JP, BarberSM, Bailey JV: Equine testicular neoplas ia. Compend Contin Educ Pract Vet 7:$53-$59,1985. 3. Jubb KVF, Kennedy PC: Pathology of Domestic Animals. 2nd ed. New York, NY: Academic Press, pp.456-460,1970. 4. Held JP, Adair S, McGavin MD, et al: Bacterial epididymitis in two stallions. J Am Vet Med Assoc 197:602-604,1990. 5. Walker DF, Vaughan JT. Bovine and Equine Urogenital Surgery. Philadelphia, PA:Lea and Febiger, p. 165,1980. 6. Rebar A, Fessler JF, Erb R: Testicular teratoma in a horse: a case report and endrocrinologic study. J Equine Med Surg 3:361366,1979. 7. Stick JA: Teratoma and cyst formation of the equine cryptorchid testicle. J Am Association Vet Med 176:211-214,1980. 8. Conway DA: A teratoma in the undescended testicle in a horse. Irish Vet J 20:226-228,1966. 9. Symth GB: Testicular teratoma in an equine cryptorchid. Equine Vet J 11:21-23,1979. 10. Kenney RM, Hurtgen J, Pierson R, et al: Manual for breeding soundness examination of stallions. J Soc Therio 9:354,1983. 11. Pickett BW, Voss JL, Bowen RA, et al: Seminal characteristics and total scrotal width (TSW) of normal and abnormal stallions. In Proceedings. Am Assoc Equine Pract 33:487-518,1987. 12. Pickett BW, Voss JL: Reproductive management of the stallion. In Proceedings. Am Assoc Equine Pract 18:501-531,1972. 13. Jasko DJ, Lein DL, Foote RH: Determination of the relationship between sperm morphologic classifications and fertility in stallions: 66 cases (1987-1988). J Am Vet Med Assoc 197:389394,1990.
EQUINE VETERINARY SCIENCE