JPC SYSTEMIC PATHOLOGY
Reproductive System
January 2022
R-M06 (NP)
Signalment (JPC #1454646): Dog
HISTORY: None
HISTOPATHOLOGIC DESCRIPTION: Testis and epididymis: Expanding the connective tissue of the epididymis are multiple granulomas, up to 3x6 mm, centered on foci of numerous degenerate spermatozoa and inflammatory cells, clear acicular clefts (cholesterol), and abundant eosinophilic cellular and karyorrhectic debris (necrosis). These areas are rimmed by a zone of lymphocytes, plasma cells, epithelioid macrophages, and rare multinucleated giant cells and are further surrounded by thin bands of fibrous connective tissue. Multifocally within the surrounding connective tissue, there are few lymphocytes, plasma cells, and occasional macrophages, some of which contain granular, golden-brown pigment (hemosiderin). Within the epididymis there is diffuse aspermia. Within the testis, seminiferous tubules are degenerate with an undulant basement membrane, vacuolated Sertoli cells, and decreased amounts of mature sperm. Multifocally in the testis low numbers of similar inflammatory cells infiltrate and surround seminiferous tubules and there are rare multinucleated spermatids.
MORPHOLOGIC DIAGNOSIS:
1. Epididymis: Sperm granulomas, multiple, breed not specified, canine.
2. Testis, seminiferous tubules: Degeneration, diffuse, moderate with hypospermatogenesis and multifocal mild lymphoplasmacytic orchitis.
GENERAL DISCUSSION:
- Reported in many domestic species and man
- May occur within the testes, efferent ductules, epididymis, and ductus deferens
- Predisposing factors include trauma, inflammation, congenital ductular abnormalities, adenomyosis of epididymal ducts, parasitic lesions, toxins, and vasectomy
- Effects on fertility depend on the location and severity of the lesion
PATHOGENESIS:
- Innate and acquired immune function is actively suppressed in testicular parenchyma, as spermatocytes, spermatids, and spermatozoa are highly antigenic and outside the blood-testis barrier
- Any defect, injury, infection, or degenerative change (trauma, rupture of duct or tubule, blind-ended efferent ductules, segmental aplasia of the mesonephric ducts [absence of the tail of the epididymis], adenomyosis, epididymitis) that results in leakage of spermatozoa or spermatozoal antigens into the extra tubular compartment incites a foreign body or granulomatous response, fibrosis, continued disruption of tubules, spermiostasis, or spermatocele
- Sperm releases into extratubular space > recruitment of CD4+ and CD8+ lymphocytes > upregulation of MHC II molecules on epithelial cells > inflammation exacerbated
- Ram studies found local immune response of IgG- and IgM-producing cells and T-helper cells early, followed by atypical foreign body reaction
- Spermatic granuloma of the epididymal head: A specific disorder of sexual development (DSD) in which efferent ductule(s) are blind ended due to failure to join with the epididymal duct during development; these blind-ended ductules fill with spermatozoa > rupture > spermatic granuloma
- Common in Saanen goats and Boston terrier dogs.
TYPICAL CLINICAL FINDINGS:
- Chronic epididymitis: Fibrosis can cause hard nodules and testicular atrophy
- May have no effect on fertility when lesions are small and isolated to a single efferent ductule, or unilateral lesions that occlude sperm transport, if the contralateral testis is normal
TYPICAL GROSS FINDINGS:
- Irregularity of epididymal size and shape in comparison to contralateral side
- Usually a single, hard epididymal nodule, although can be multiple
- Fibrinous or fibrous adhesions between epididymis and tunics
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Accumulations of spermatozoa and macrophages within tubules or the adjacent interstitium of efferent ductules or epididymis
- Ducts contain fibrin, neutrophils, disintegrating spermatozoa, damaged epithelium, macrophages, multinucleate giant cells with engulfed spermatozoa
- Macrophages form a distinct layer in the granuloma wall, external to the mass of extravasated spermatozoa
- Foreign body and Langhans type multinucleate giant cell macrophages
DIFFERENTIAL DIAGNOSIS:
- Epididymitis due to Brucella ovis, Histophilus ovis, or Actinobacillus seminis in rams
- Neoplasia
COMPARATIVE PATHOLOGY:
- Marked species variation in development of post-vasectomy sperm granulomas
- Rabbit, hamster, and monkey: Sperm granulomas usually do not appear for weeks to months after vasectomy; can occur anywhere along the epididymis and ductus deferens
- Guinea pigs: Vasectomized animals develop autoimmune orchitis rather than granulomas
- Spontaneous epididymal lesions in captive aged chimpanzees: lymphocytic infiltrates (3/14), hemosiderophages (2/14), and a sperm granuloma (1/14) (Chaffee, Vet Pathol. 2016)
REFERENCES:
- Chaffee BK, Beck AP, Owsteon MA, Kumar S, et al. Spontaneous reproductive tract lesions in aged captive chimpanzees. Vet Pathol. 2016;53(2):425-435.
- Foster RA. Male reproductive system. In: McGavin MD, Zachary JF, eds. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Mosby Elsevier; 2017: 1196-1999, 1202-1203, 1208-1210, 1218
- Foster RA. Male genital system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 3. 6th ed. Philadelphia, PA: Saunders Elsevier; 2016: 467-468, 480-481, 497.
