JPC Systemic Pathology

Reproductive System

January 2025

R-M04

 

 

SIGNALMENT (JPC # 2755480): A 4-year-old bearded collie

 

HISTORY: This dog presented with clitoral enlargement, and progesterone levels cycled normally with estrus, indicating ovulation.

 

HISTOPATHOLOGIC Description: Gonad: The gonadal tissue is composed of a peripheral zone of ovarian tissue, which surrounds a central zone of testicular tissue. The ovarian tissue is composed of ovarian stroma which surrounds ovarian follicles in various stages of development and several variably sized (up to 3mm in diameter) corpora lutea. There are numerous primordial follicles deep to the tunica albuginea, each with a primary oocyte and surrounded by a single layer of flattened follicular cells. Primary follicles contain a larger oocyte which is surrounded by a zona pellucida, further surrounded by a single layer of cuboidal to columnar follicular granulosa cells. Secondary follicles contain a primary oocyte which is rimmed by a zona pellucida and is surrounded by a radially arranged cluster of granulosa cells (corona radiata) with a small fluid filled antrum, and the zona granulosa is bounded by the theca interna and theca externa. Tertiary follicles (Graafian follicles) contain large, fluid-filled spaces between granulosa cells which fuse to form a large antrum filled with basophilic to amphophilic homogenous material; oocytes are out of section in the few tertiary follicles present. There are scattered atretic follicles with a swollen, undulant zona pellucida. The corpora lutea consist of granulosa lutein cells surrounded by theca lutein cells. The testicular tissue is composed of hypoplastic seminiferous tubules that lack germ cells and spermatozoa and are lined by Sertoli cells that extend from the undulant basement membrane into the lumen. Interstitial cells are interspersed between hypoplastic tubules and have small, round nuclei and eosinophilic, foamy cytoplasm.  

 

Oviduct: Essentially normal tissue.

 

Morphologic diagnosis: Gonad: Ovotestes, bearded collie, canine.

 

Condition: XX, SRY-, ovotestes disorder of sexual development (DSD), with female phenotype

 

GENERAL DISCUSSION: 

• The terms “hermaphrodite”, “intersex”, and “pseudohermaphrodite” should be avoided in favor of “disorders of sexual development” (DSD) with a more complete description including sex chromosome (i.e. XX, XY), SRY presence, gonad type, tubular genitalia, and external genital phenotype 

• DSD occur in all domestic species 
• Most XX, SRY- conditions are normal females with cystic remnants of ducts or tubules 

• Caused by genetic or chromosomal abnormalities or inappropriate hormone exposure at the time of reproductive tract differentiation

 

PATHOGENESIS:

• Sexual development occurs in three steps: 

• 1) Establishment of chromosomal/genotypic sex
• 2) Determination of gonadal sex
• 3) Development of phenotypic sex; a functional testis is critical to male phenotypic development

• Chromosomal sex is determined at fertilization: XX or XY

• Disorders are either XX or XY DSD
• Rarely, aneuploidy can occur resulting in XXX, XXY (Kleinfelter-like syndrome), or X_ (Turner-like syndrome) 

• Normal gonadal sex is determined by a variety of genes:

• Female:

• XX chromosomal sex lacks the SRY and testis-determining factors 
• WNT4 is important and upregulates folistatin (FST) and DAX1; it also inhibits SOX9 (a male specific gene)
• FOXL2 and BMP2 also are important in upregulation of FST
• Wolffian (mesonephric, male) ducts regress in the absence of SRY gene product
• Outer cortical layer of bipotent gonad becomes ovarian tissue first - ovotestes are usually ovarian tissue on the periphery with varying amounts of testicular tissue in the medulla

• Male:

• SRY gene is the sex determining region of the Y chromosome                
• In the presence of SRY, SOX9 expression is increased, promoting the testicular pathway and blocking the ovarian pathway
• SRY is also important in early Sertoli cell differentiation

• Complete sexual reversal (XX, SRY-): Gonad is not the type corresponding to the XX or XY genotype of that individual

• Mice: Autosomal dominant gene (Sxr) acts like a Y chromosome; autosomal dominant 
• Dogs, pigs, and goats: Similar gene, but autosomal recessive 

• XX Ovotesticular female DSD (XX sex reversal): Common in pigs; unknown mode of inheritance
• Polled intersex syndrome (PIS): Deletion of 11.7 kb PIS region of chromosome 1 

• PIS à regulates FOXL2 (an ovarian determining gene) à normally inhibits DMRT1
• DMRT1 à regulates SOX9 (a testicular determining gene)
• With deletion of PIS, FOXL2 is inactive and cannot inhibit DMRT1, which then allows for masculinization via SOX9 (male goat with XX chromosomes)

• XX, SRY- dogs: unknown cause; potentially due to SOX9 mutation

• American cocker spaniels are particularly susceptible

• Phenotypic sexual development: Abnormal sexual development often leads to abnormal appearing external genitalia

• Female tubular and external genital development form from paramesonephric (Mullerian) ducts – will develop in the absence of hormones
• The presence of testosterone and anti-Mullerian hormone (AMH) cause regression of paramesonephric (Mullerian, female) ducts and development of mesonephric (Wolffian) ducts into male genitalia and accessory sex glands
• AMH is produced by Sertoli cells and testosterone is produced by interstitial (Leydig) cells 

• Ovotestis usually results in varying degrees of masculinization of the tubular and external genitalia – e.g. clitoral hypertrophy, hypospadias

 

TYPICAL GROSS FINDINGS: 

• Complete sexual reversal (XX, SRY-): XX chromosomes; phenotype is male (testes and male tubular genitalia)
• XX Ovotesticular female DSD (XX sex reversal): Gonads are often ovotestes; testes may lack germ cells; ovulation and pregnancy are reported
• Polled intersex syndrome (PIS): 

• Heterozygous: Polled with no affect on sexual differentiation
• Homozygous: Polled with a wide range of masculinization

• XX, SRY- dogs: Range from XX, SRY- testicular to XX, SRY- ovotesticular; male components are sterile
• Ovotestis

• Bilateral - ovotestis on each side
• Unilateral - ovotestis on one side and ovary or testis on opposite side
• Lateral - testis on one side and ovary on the other 
• Masculinization of tubular and external genitalia (varying degrees)

 

Typical LIGHT Microscopic Findings: 

• Ovotestis - testicular portion always located in medulla with the ovarian tissue external to it, located in the cortex

• Testicular portion - Hypoplastic seminiferous tubules lined by Sertoli cells;    interstitial cells between hypoplastic tubules; rare or absent germ cells
• Ovarian portion with oogonia, oocytes, primary and secondary follicles
• Relative quantities of testicular versus ovarian tissue varies dramatically between affected individuals

 

Differential Diagnosis: 

Anomalies of sexual development in various species:

• Cryptorchidism - most common disorder of sexual development in the dog
• Ovarian agenesis - ruminants, swine, dogs
• Ovarian dysgenesis - horses; small, inactive ovaries that lack germ cells
• Ovarian hypoplasia and genital infantilism - occurs in many species, but described primarily in cattle

• Swedish Highland cattle - occurs as a genetic defect

• Testicular hypoplasia 

Drug-Induced intersexuality: 

• Androgens and many progestins induce masculinization of the genitalia in female offspring of rats, mice, guinea pigs, rabbits, cattle, sheep, dogs, monkeys, and women

• Estrogens, progestins, and antiandrogens - feminization of the reproductive tract and external genitalia of the male rat fetus 
• Testosterone given to pregnant bitches induces female pseudohermaphrodites (i.e. XX, SRY-, variably male phenotype) in her offspring; male offspring are normal

 

Comparative Pathology: 

• European roe deer: Congenital DSDs carrying from antlered females to true hermaphrodites
• Anurans: Intersex associated with exposure to endocrine disrupting chemicals such as herbicide atrazine, polychlorinated biphenyls (PCBs), bisphenol A, and estrogenic compounds

Specific, well described anomalies of sexual development:

• Freemartinism - abnormality of chromosomal sex, chimerism (XX/XY)

• Reported primarily in cattle; rarely in sheep, goats, and swine (don’t usually have shared placental circulations)
• Freemartin is the female born as co-twin to male calf; female twin exhibits masculinization and is sterile, male twin minimally affected
• Anastomoses develop between the placental circulations > true chimerism of hematopoeitic cells, and androgenic hormones from male fetus reach female fetus > suppress female genital system and allow male vestiges to develop in the female
• Gross findings include: Female phenotype; stunted gonads; paired hypoplastic seminal vesicular glands; hypoplastic seminiferous tubules (ovotestes); hypoplastic internal uterine tubes, a short nonpatent vagina, vestibule, a small vulva with prominent tuft of hair; and enlarged clitoris
• Vesicular glands always present

• Androgen insensitivity (XY, SRY+, cryptorchid testes, female external genitalia; AKA testicular feminization, XY sex reversal, male pseudohermaphrodite)

• Mice, rats, cattle, and horses
• Inherited form of XY DSD (female external genitalia and cryptorchid testis) transmitted by females to half of their offspring
• Mutation in the Tfm (testicular feminization) gene > deficiency of intracellular androgen receptors, rendering all cells insensitive to androgens; or lack of AMH
• Equine male pseudohermaphrodites have normal female external genitalia but show male behavior patterns - unique to horses

• Persistent Mullerian Duct Syndrome (PMDS) - rare disorder of AMH production or function

• Miniature Schnauzers and goats

• Tortoiseshell/calico male cat 

• XXY sex chromosome constitution (Klinefelter-like syndrome)
• Gene for black and gene for orange are carried one per X chromosome (normal male should not have both hair colors)
• Testicular hypoplasia and sterility

 

REFERENCES:

1. Foster RA, Premanandan C. Female Reproductive System and Mammae. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 7th ed. St. Louis, MO: Elsevier; 2022:1271-1274.
2. Foster RA. Male Genital system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol. 3 6^th ed. St. Louis, MO: Elsevier; 2016:468-471.
3. Howerth EW, Nemeth NM, Ryser-Degiorgis MP. Cervidae. In: Terio KA, McAloose D, St. Leger J, eds. Pathology of Wildlife and Zoo Animals. London, UK: Academic Press; 2018:152. 
4. Pessier AP. Amphibia. In: Terio KA, McAloose D, St. Leger J, eds. Pathology of Wildlife and Zoo Animals. London, UK: Academic Press; 2018:929. 
5. Schlafer DH, Foster RA. Pathology of the genital system of the nongravid female. In: Maxie MG, ed. Jubb, Kennedy and Palmer’s Pathology of Domestic Animals. Vol 3. 6th ed. St. Louis, MO: Elsevier; 2016:361-366.

Click the slide to view.

---