This page is part of the Veterinary Reproductive Pathology website

Dr Rob Foster

OVC Pathbiology

University of Guelph


Bovine Testicular Pathology

Table of Contents

Disease of the testis

 


 

 

 

The two main concerns with disease of the testis (and epididymis) as well as the rest of the reproductive tract are infertility and diseases that cause morbidity or mortality. Infertility is usually the domain of the theriogenologist (therí(on) is Greek for beast and gén(os) is Greek for offspring or sex) and the pathologist can contribute by identifying the underlying reason or diagnosis and the cause. Male infertility is a combination of lack of production of spermatozoa, production of viable spermatozoa, transportation and maturation of spermatozoa and being able to deposit the spermatozoa in the appropriate location mixed with seminal fluid..

 

Aspermia and Azoospermia

Aspermia is the inability to produce semen. Azoospermia is a lack of spermatozoa in semen.

Inflammation of the testis - Orchitis

General considerations

From a pathology point of view, orchitis is inflammation of the testis. Clinically though, orchitis is used to indicate any disease of the scrotal contents, including periorchitis, epididymitis and orchitis itself.

Macroscopic orchitis is identified clinically as a swollen painfull testis and is usually accompanied by epididymitis and or periorchitis. This is so much so that epididymitis and orchitis is combined as the term epididymoorchitis.

Apart from bulls in areas endemic for Brucella abortus or tuberculosis, and in some cases of epididymitis, orchitis is a rare and sporadic disease in domesticated animals.Focal accumulations of lymphocytes are occasionally seen in the testes of most species as incidental findings. Lymphocytic (or nonsuppurative) inflammation is seen in some infertile animals; an immunological pathogenesis is invoked as immunization of guinea pigs and bulls with spermatozoa induced inflammation of the rete testes especially. Efferent ductules are also involved experimentally.

Orchitis as the primary and severe disease has historically been attributed to brucellosis or tuberculosis. Tuberculous orchitis is a multifocal granulomatous disease that is much less common now because of eradication in many countries. Brucellosis is similarly reduced in prevalence. Brucella abortus, causes orchitis as a dominant change.

Interstitial orchitis may not be recognized macroscopically, but histologically there are lymphocytes in the interstitial stroma, with concurrent or subsequent fibrosis. In bulls, small clusters of lymphocytes are frequently observed adjacent to seminiferous or rete tubules or efferent ductules of otherwise normal testes. In stallions, interstitial perivascular lymphocytic foci are particularly common and occur in areas of degeneration. Lymphoid aggregates are frequently seen in beagle dogs used as laboratory animals. Foci of lymphocytes in cats are considered an age-associated change.

Bacterial orchitis

Brucella abortus

Olsen and Palmer (2015) review basic information about brucella infection in animals.

The best descriptions of orchitis are of Brucella abortus infection in endemic regions. In most instances, the orchitis is acute and severe. It may be unilateral but affected animals are sterile. The scrotum swells and is hot and doughy due to inflammatory changes in the tunics and to a lesser extent in the epididymis. Swelling of the testis is limited by the inability of the testicular capsule to stretch, and any swelling constricts venous and then arterial flow causing infarction. The cavity of the vaginal tunics distends with fibrinopurulent exudate. Scattered yellow foci of necrosis coalesce to produce total testicular necrosis. Sequestration by inflammation and thickening of the tunics follows. Sometimes the necrotic parenchyma liquefies and the organ then is a pus-filled cavity surrounded by a thick connective-tissue capsule. Rupture may occur but is unusual.

Microscopically, the inflammation of the tunics results in extremely dense adhesions between the parietal and visceral layers. Within the testes, the infection appears to progress along the lumen of the seminiferous tubules. The seminal epithelium becomes necrotic and desquamates. Large numbers of the organisms are visible in the lumen. At the early stage, neutrophils, macrophages and lymphoid cells are in the interstitial tissues and form cuffs about the tubules. The tubules and the interstitial tissues then become necrotic. There is often focal necrotizing epididymitis complicated by the development of spermatic granulomas.

Olsen SC, Palmer MV. Advancement of knowledge of Brucella over the past 50 years. Vet Pathol. 2014; 51: 1076-1089.

Mycobacterial orchitis - tuberculosis

Tuberculous orchitis in bulls is an uncommon lesion, even in areas of endemic infection. The granulomatous response to the tubercle bacilli is similar to the granulomas that occur to spermatozoa. Involvement of the testis may be either miliary or regional. In the miliary form, small or large caseous and mineralized foci are irregularly scattered throughout the testes but may spare the epididymis entirely. The path of infection is probably intratubular from a primary epididymal lesion.

Other bacterial orchitis

Other bacteria causing orchitis in bulls, sometimes with overt abscessation, include streptococci, staphylococci, Trueperella pyogenes, Escherichia coli, Histophilus spp., and Salmonella spp, Actinomyces bovis, Actinobacillus sp., and Nocardia sp. In nocardiosis especially, the lesions are at first nodular but ultimately transform the whole testis into an abscess, the capsule of which is the vaginal tunic.

Chlamydial orchitis

Infection of bulls with Chlamydia spp. causes orchitis, and in field cases, focal granulomatous lesions are observed. The spontaneous occurrence of orchitis and epididymitis due to Mycoplasma sp. infection is reported.

 

Viral orchitis

In bulls, many viruses have been isolated from testes or semen. Histological changes are seldom found. Persistent infection with bovine viral diarrhea virus results in spermatozoal defects, but no distinct histologic lesions in the testis. Severe interstitial orchitis and testicular degeneration and inflammation of spermatic arteries occur in bovine malignant catarrhal fever (Alcelaphine herpesvirus 1 and ovine herpesvirus 2). In experimental bluetongue virus infection in bulls, interstitial orchitis accompanies arteritis. Clinical orchitis and aspermatogenesis were listed as findings in bovine enterovirus 1 infection, but lesions are not described. A focal nodular orchitis is reported in lumpy skin disease (lumpy skin disease virus) of bulls.

Protozoal orchitis

Besnoitia besnoiti

Orchitis in bulls infected with Besnoitia besnoiti is reported. The cysts were in the interstitium.

Kumi-Diaka J1, Wilson S, Sanusi A, Njoku CE, Osori DI. Bovine besnoitiosis and its effect on the male reproductive system. Theriogenology. 1981; 16: 523-530.

Testicular necrosis

Testicular necrosis is where there is death of regions of the testis. It usually affects the whole testis, but in some species (bull and ram) can be a segmental disease. The blood flow to the testis is via a tortuous testicular artery that is part of the pampiniform plexus. By the time the blood reaches the testis, it is barely pulsile and has a lower pressure than normal arterial pressure. A slight change in flow will result in ischemia. This fortunately does not occur very often. Necrosis of the testis is particularly seen in retained (or cryptorchid) testes, and is assumed to occur because of an avascular event, particularly. Torsion of a fully descended testis is virtually unheard of in all species expect for the horse.

Testicular torsion (torsion of the spermatic cord)

 

Testicular rupture

 

 

Polyorchia

Polyorchia is a very rare condition w

 



Small testes


Anorchia - No testis,

The failure to find one or both testes in the scrotum becomes a clinical challenge. If there results of endocrinological testing indicate functional testicular tissue , the first condition to exclude is cryptorchidism (also called retained testis). Surgery to remove the retained structure will hopefully reveal a testicular structure, and there will be no need for histological examination. On occasion, pathologists get involved when the deferent duct is found on exploratory surgery but there is no testis. The major possibilities therefore become

·         Previous surgical removal

·         Testicular hypoplasia

·         Testicular atrophy/necrosis

·         Testicular aplasia

Previous surgical removal

When there has been previous surgical removal, the end of the deferent duct can be found, and usually the ductus is well developed and at a size commensurate with the size of the ductus at the age of castration or removal. No epididymal tissues or embryonic remnants should be present.

Testicular atrophy/necrosis

The retained testis is hypoplastic, virtually by definition, as the raised temperature compared to scrotal testes prevents spermatogenesis. Further details are listed below under cryptorchidism. Testes retained in the abdomen, despite their hypoplastic nature, also undergo a process of degeneration and they will atrophy. The process is a degenerative one, the histological appearance is that of degeneration, but the macroscopic change is atrophy - this is the convention used to define these particular terms as they apply to the testis. For further information about testicular degeneration, see the section below.

The process of degeneration of a retained testis is thought to mirror the degenerative changes of a scrotal testis, although the lack of spermatogenesis or spermatic arrest already exists. Tubules shrink in size, the basement membranes become wavy, and with time, the Sertoli cells disappear so that all that remains is an outline of the previous tubule. The epididymis remains as a hypoplastic tube, but over time, it too may 'fade'and only a vestige remains. This usually occurs after the testis becomes completely degenerate. On occasion, the testis suffers a severe process where it dies, and the necrosis is assumed to be a vascular event. Torsion of the retained testis can occur and both testis and epididymis will be affected.

 

Testicular aplasia

 

 

Cryptorchidism (Retained testes)

Cryptorchidism is infrequently reported in bulls but the prevalence is much higher. Retention of the testis and epididymis is mostly in the subcutaneous/inguinal region, and occurs about twice as often on the left as compared to the right side. Polled Hereford and Shorthorn cattle are more at risk than other breeds. Little is known of the pathogenesis of cryptorchidism in bulls, although it is believed to be hereditary. The histological appearance of the cryptorchid testis is similar to that of hypoplastic testes and epididymides. Neoplasia in cryptorchid testes is very rare, with an interstitial cell tumor and a fibrolipoma (Osawa et al 2011) reported.

Testicular hypoplasia

Testicular hypoplasia is where the testis does not develop to its normal size. It is always accompanied by a failure of the epididymis to acquire its normal size. Most cases of hypoplasia are because of cryptorchidism, but in this section, primary hypoplasia is limited to those situations where the testis has descended normally. Hypoplasia is almost always seen as a failure of the prepubertal testis to enlarge, but there may be cases where even the prepubertal testis is smaller than normal. Hypoplasia is best diagnosed clinically by identifying that the testis has not increased in size from puberty.

Testicular hypoplasia in bulls, and especially in some breeds such as the Belgian blue, is very common. Breeding soundness examination and the culling of bulls with a scrotal circumference below the normal range, is common and in some breeds exceeds 90% of tested individuals. The causes are probably multifactorial. Studies suggest it is hereditary in the Swedish Highland breed, where it has a recessive inheritance with incomplete penetrance. Animals with white body and ears are particularly likely to have hypoplasia. The majority of unilateral hypoplastic testes are on the left side. In one Bos indicus breed, heritable hypoplasia is linked to branching of the testicular artery near the aorta of the same side, suggesting that reduced blood flow may be responsible. Testosterone secretion was reduced in the affected testis.

 

Microscopic changes of hypoplasia include cessation of spermatogenesis at some stage, with either degeneration or excessive apoptosis of the germinal epithelium. The most severe cases of hypoplasia have a Sertoli cell-only pattern or they have some normal and abnormal tubules intermixed, often with affected tubules being in the more dorsal part of the testis.

 

Bovine viral diarrhea virus

Persistent infection of bulls with bovine viral diarrhea virus (BVDV) may affect testicular development. Borel et al (2007 reported on a 16 month old bull that was persistently infected wtih BVDV and virus was found in the Sertoli cells and virtually all epithelial cells of all reproductive tissues.

 N. Borel, F. Janett, K. Teankum, K. Zlinszky, C. Iten and M. Hilbe (2007) Testicular Hypoplasia in a Bull Persistently Infected with Bovine Diarrhoea Virus. J Comp Path 137: 169-173

 

Genetic - Robersonian translocation

Centric fusion (Robertsonian translocation) is a defect where there are fused chromosomes and in meiosis there is unequal partitioning of genetic elements. There is theoretically a 2/3 reduction in fertility as embryos die in early gestation. In reality, the reduction in fertility is 7-21%. It is found in 70 different breeds. CF positive cows from CF positive sires culled for early embryonic mortality.

Bulls with centric fusion had apoptosis of spermatids.

 

Alvin F. Weber, James Waddell, Mel L. Fahning, Lance C. Buoen, and Bradley E. Seguin (2007) Cytologic and ultrastructural evidence of spermatid selection in a 1/29, 14/20 centric fusion bull. Can Vet J. 2007 December; 48(12): 1255–1257.


Testicular atrophy – degeneration.

Testicular atrophy is when the testis becomes smaller in size. It is a macroscopic term, whereas the corresponding microscopic change is degeneration. It is difficult to differentiate atrophy from hypoplasia, and a knowledge that the testis became smaller is important.

 

Pathogenesis

Mainenance of the seminiferous epithelium requires a close intergration of pituitary hormones, systemic and local environments, and of the crosstalk between germ cell, Sertoli cell and interstitial endocrine cell. Injury to any one of these ill upset the equilibrium necessary for normal spermatogenesis.

The causes of testicular atrophy – degeneration are legion. Here are some of the known causes, and some are discussed further below.

Heat

§  high environmental temperature

§  fever

§  epididymitis and orchitis

§  scrotal dermatitis

§  scrotal edema

§  periorchitis

 

§  irradiation

§  poor health and debility

§  advancing age.

§  hormones

§  estrogen

§  Sertoli cell tumours

§  drugs

§  chemotherapy

Toxicosis

Feeding bulls cotton seed meal is known to affect fertility and cause testicular atrophy (AVJ 72: 463)

Age associated degeneration

Humphrey and Ladds (1975) examined 80 normal range bulls from Tropical Australia and found 2 main changes with advancing age. Firstly they extablished that the dorsal part of the testis has less interstitial collagen than the middle or ventral parts. With age, there was progressive intertubular fibrosis and especially of the ventral testis. There was a reduction of the tubular area with age. Lymphocytes and plasma cells increased in number progressively with age and especially in very old bulls.

Humphrey JD, Ladds PW (1975) A quantitative histological study of changes in the bovine testis and epididymis associated with age. Research Vet Sci 1975: 19: 135-141

 

Macroscopic changes

 

Microscopic changes

 

 

Irradiation

Irradiation of the testis results on injury to the germ cells and Sertoli cells. Amounts above 6 gy had a dose dependent effect on the seminiferous tubule by reducing Sertoli cell numbers and spermatogenesis. Above this level where was permanent damage to the tubules by reducing the number of spermatogonia and Sertoli cells.

Herrid M, Davey R, Stockwell S, Schmoelzl S, Uphill G, Poirier V, Hope M, Hill JR, Holland MK, Lehnert SA. Depletion of testis cell populations in pre-pubertal Bos indicus cattle by irradiation. Anim Reprod Sci. 2013; 141: 124-130.

 

Large testes

Testicular dissymmetry is a common clinical presentation. Because neoplasia is so common, the natural tendency for clinicians is to assume that the larger testis is abnormal and potentially contains a neoplasm. The larger testis may be presented for examination. Consideration for testicular dissymmetry should be given for another possibility - unilateral testicular atrophy. A combination of changes may be operative, and should be considered when the larger testis is grossly 'normal'. One may be smaller, and the other larger. Neoplasia is a common cause of testicular enlargement, and some testicular neoplasms cause testicular atrophy of the contralateral testis. Testicular hypertrophy is seldom considered though. The list of conditions causing testicular enlargement therefore include

§  neoplasia (primary)

§  neoplasia (secondary)

§  hypertrophy

§  orchitis

§  cystic rete testis

§  rete cysts

§  spermatocele

Compensatory hypertrophy

The testis is capable of hypertrophy. This enlargement is not dramatic. The basis is believed to be a greater stimulation of interstitial endocrine cells and Sertoli cells by the hormones of pituitary origin (LH and FSH) that are not inhibited in a negative feedback system.

 Enlargement of an otherwise normal testis is rarely a primary disorder. Secondary or compenstory hypertrophy is a unilateral condition that indicates an underlying disease in the contralateral testis. It is a well-recognized phenomenon in hemicastrates, and in hypoplasia, cryptorchidism (Fig 5.3), or atrophy of the contralateral testis (Fig 5.25). In rams and bulls, hypertrophy occurs when the unilateral condition is present during the peripubertal period, and with increased FSH production. The increase in size can be double and is due to an increase in the diameter and and length of the seminiferous tubules with more numerous and larger Sertoli cells and more germinal cells per Sertoli cell. Hemicastration of prepubertal boars, especially in those younger than 3–4 months, results in dramatic hypertrophy of the contralateral testis.

 

 

Hyperplasia of testicular elements

Hyperplasia of testicular elements is an unusual finding. Despite a greater number of particular elements, hyperplasia does not cause enlargement of the testis. It is a microscopic finding usually. There is no known link with neoplasia.

Interstitial cell hyperplasia

 

Sertoli cell hyperplasia

 

Testicular neoplasia

It is difficult to answer the question 'What is the most common primary tumor of the testis of the bull?'. Numerically based on reports - Interstitial cell tumors win. All tumors typically occur in older animals -with the exception of some germ cell tumors. The occurrence of testicular neoplasms is sporadic. Bull calves have a variety of tumours including Sertoli cell tumours, interstitial cell tumours and yolks sac tumours.

Sex cord - stromal (gonadostromal) tumours

Neoplasms with a phenotype resembling the cells that originate from stroma or sex cords of the primitive gonad include the interstitial cell tumour and Sertoli cell tumour.

Interstitial cell tumour

Like all testicular tumors in bulls, interstitial cell tumours in bulls are rare. Of the primary testicular tumours, The most common is probably the interstitial cell tumor (McEntee 1990).

The largest series is reported by Dunn and McEntee (1964) and McEntee (1990). In the initial publication, 20 interstitial cell tumors were found. Subsequently, McEntee (1990) added 23.

The other reports are single case reports. Lopez et al (1994) report a single case in a one month old cryptorchid shorthorn calf.

 

López A, Ikede B, Ogilvie T (1994) Unilateral interstitial (Leydig) cell tumor in a neonatal cryptorchid calf. J Vet Diagn Invest 6:133-135 (1994).

McEntee K (1990) Reproductive Pathology of Domestic Mammals. Academic Press, San Diego. p284-285

 

Sertoli cell tumour

Sertoli cell tumours are the most commonly reported primary testicular neoplasm of the bull.

In an abattoir survey of 1598 bulls, mostly of the Shorthorn breed, Ladds and Saunders (1976) found six testicular tumours, all Sertoli cell tumours. These have the typical features of Sertoli cell tumours in other animals. They initially considered these tumours to be nodules of hyperplasia, however their size and arrangement was later considered to be more consistent with neoplasia. They were between one and 3 cm in diameter and were only identified when the testis was bisected sagittally. Three were in the right testis, two were in the left testis and the remaining one was unknown. They were all expansile tumours with no evidence of invasion

The microscopic features were typical of Sertoli cell tumours and all had a tubular pattern. The major difference between these and those seen in other species was the presence of intratubular concrements that were PAS positive.

 

Palmer et al (1980) reported on two newborn Shorthorn calves with what they believed to be Sertoli cell tumours. their photomicrograph is showed a lot of vacuolated mesenchymal tissue which is somewhat reminiscent of the yolk sac tumour.

 

Luby et al (2007) wrote a case report about a Sertoli cell tumor in a 29 month old bull with right sided SCT. The tumor was CK-, vimentin +, and S100-. It was called malignant as there was intravascular invasion of vessels in the testis, epididymis and spermatic cord.

 

Jensen et al (2008) reported on a Simmental bull with a metastatic Sertoli cell tumour of the right testis. metastases were to the pampiniform plexus. Immunohistochemistry was done for cytokeratin, vimentin and S100 but the neoplasm was only positive for vimentin..

 

In one study where bulls and buffaloes were kept until 9–14 years for draft purposes, 20 of 161 testes examined contained neoplasms; all but one were Sertoli cell tumors. Seven tumors were in undescended testes. In contrast to dogs, bovine Sertoli cell tumors are often in newborn or young calves, suggesting altered embryogenesis. They sometimes have laminated intratubular concretions resembling those seen in bovine testicular hypoplasia and cryptorchidism. A simultaneous occurrence of Sertoli cell tumor and epididymal aplasia was observed. One bovine Sertoli cell tumor was in a testis of an animal in which castration by the burdizzo method was attempted 5 years previously. Metastasis of Sertoli cell tumor to the pampiniform plexus is reported in a bull; there is no clear evidence of a hyperestrogenism syndrome.

Jensen KL, Krag L, Boe-Hansen GB, Jensen HE, Lehn-Jensen H (2008) Malignant Sertoli Cell Tumour in a Young Simmenthal Bull – Clinical and Pathological Observations. Reprod Dom Anim 2008; 43, 760–763

 

Ladds PW, Saunders PJ (1976) Sertoli cell tumours in the bull. J Comp Pathol 1976; 86: 503-508.

Luby CD, Middleton JR, Youngquist RS, Kim DY, Evans TJ (2007) Theriogenology Question of the Month J Amer Vet Med Assoc 2007; 231: 1503-1505.

Palmer NC, A.B. King AB, Basrur PK (1980) Sertoli Cell Tumor in Two Related Newborn Shorthorn Calves. Canadian Vet J 1980; 21: 317-319

Testicular germ cell tumors

(TGCT)

Neoplasms of the testis categorized as germ cell tumours (GCT) have a phenotype of spermatogonia or spermatocytes, or different embryonic types (ectoderm (including neuroectoderm), mesoderm, and endoderm). The germ cells of the normal testis arise in the yolk sac and migrate to the testis. These cells have an amazing degree of pluripotency, being able to differentiate to any tissue in the body. Seminomas are the most common TGCT. All the others are grouped as non seminomatous GCT (NSGCT)

Seminoma

 

 

Prognosis

 

Macroscopic findings

 

Microscopic findings

 

 

Nonseminomatous germ cell tumor (NSGCT)

 

Teratoma

I have yet to see a report of teratoma in a bull or bull calf.

Embryonal carcinomas

There is a single case of embyronal carcinoma reported in a bull calf. The calf had multiple masses within its abdomen and no testes in the scrotum. The masses were those of a carcinoma with different phenotypes including solid, papillary, ductal and cystic regions within a fibrous stroma. The cells stained for alpha-fetoprotein (AFP), placental alkaline phosphatase (PLAP), cytokeratin, and carcinoembryonic antigen (CEA) but were negative for Wilms tumor 1 protein (WT1),e and vimentin.

Aihara N, Yamamoto N, Takagi T, Une Y (2011) Embryonal carcinoma in the abdominal cavity of a male calf. J Vet Diagn Invest 2011; 23: 598-602.

Yolk sac tumors

These neoplasms have features reminiscent of endoderm and yolk sac differentiation. The embryonic endoderm is divided into the visceral and parietal components. The visceral is the roof of the cavity and gives rise to the organs of the foregut (lung liver stomach, thyroid pancreas), midgut and hind gut (small and large intestine, bladder). and the visceral becomes the lining of the yolk sac. The yolk sac has a layer of endoderm, a layer of spindle shaped cells (of endodermal origin) and a mesothelial layer. They all secrete alpha fetal protein.

The histological features are the presence of the reticular-microcystic appearance with mesenchymal tissue and microcysts. Some have endodermal sinus differentiation (Duval or Schiller-Duval sinuses or bodies) where are tubulopapillary sinusoidal structures of cuboidal or columnar structures with a vascular core. Other potential patterns include polyvesicular, and tubular patterns. As haematopoietic progenitor cells come from the yolk sac, they may be present in tumors.

A small number of calves with yolk sac tumors are reported. Palmer et al (1980) reported on two newborn Shorthorn calves with what they believed to be Sertoli cell tumours. Their photomicrograph is showed a lot of vacuolated mesenchymal tissue which is somewhat reminiscent of the yolk sac tumour. One of the first confirmed you accept tumours was in 28 day old Japanese black calf that had multiple nodules throughout the abdomenal cavity. Similar masses were in the scrotum but there were no testes (Kagawa et al 1998). A similar presentation was reported by Sasaki et al (2012) however that case was thought to begin in the abomasum. Sakaguchi et al (2013) reported a case in the right testis of a newborn Holstein calf.

 

Kagawa Y, Ohosaki A, Ohosaki R, Katsuta O, Tsuchitani M, Taniyama H (1998) Yolk sac carcinoma in a calf. Vet Pathol 1998; 35: 220-220.

Nogales FF, Preda O, Nicolae A (2011) Yolk sac tumours revisited. A review of their many faces and names. Histopathology 2011; 60: 1023-1033

Palmer NC, A.B. King AB, Basrur PK (1980) Sertoli Cell Tumor in Two Related Newborn Shorthorn Calves. Canadian Vet J 1980; 21: 317-319

Sakaguchi K, Matsuda K, Suzuki H, Yamamoto N, Kondo Y, Ando T, Koiwa M, Kagawa Y, Taniyama H (2013) Testicular yolk sac tumor of myxomatous, reticular, and polyvesicular vitelline type in a newborn calf. J Vet Diagn Invest 2013; 25: 811-815.

Sasaki H, Goyama T, Noda Y, Matsumoto K, Kobayashi Y, Inokuma H. (2012) Perforating abomasal ulcer caused by yolk sac tumor in a Holstein calf. J Vet Diagn Invest 2012; 24: 804-806

 

 

Mixed seminoma and nonseminomatous germ cell tumor
 

 

 

 

Mixed germ cell - sex cord stromal tumours (gonadoblastoma)

 

 

 

Neoplasms of the collecting system (including the rete)

This section is restricted to neoplasms only. If we choose to use the term 'tumour' as a swelling, then tumours can also be cysts! Cysts of the testis are described below.

Rete neoplasms

The collecting ducts of the testis include the rete testis and efferent ductules. Neoplasms of these ductules are epithelial in type, so epithelial tumors of the testis are believed to be derived from these. Neoplasms with an phenotype resembling epithelial tissue can also be part of a teratoma (or teratocarcinoma) and occasionally, cystic Sertoli cell tumours can have an epithelial appearance. It is important to perform multiple sections to exclude teratome and to do immunohistochemistry for various cytokeratins to positively identify the neoplastic cells as epithelial.

 

 

Miscellaneous primary neoplasms

The presence of cells from a wide range of tissue types means that neoplasia of those cells can result in an almost infinite range of neoplasms. This reported in case reports or other sites are indicated below.

Hemangioma/hemangiosarcoma

 

Histiocytic sarcoma

Fibrolipoma

Osawa et al (2011) report on a testicular tumor in a bull calf where the testis was replaced with mature adipocytes and fibrous septa.

 

Osawa T, Miura M, Yamagishi N, Kim D, Fukuda N, Fukoka H, Sasaki J, Goryo M (2011) Fibrolipoma of a Cryptorchid Testis in a Young Bull. J Vet Med Sci 2011; 73: 1253-1255

Tumours metastatic to the testis

Testes are not routinely examined in animals with metastatic neoplasia, and, if a metastatic disease is present and the testis is found to have a metastasis, mention is made in the report, but an electronic literature search is unlikely to find it. One might expect the most likely candidate would be lymphoma. Melanoma and transitional cell carcinoma are both sufficiently widespread to involve the testis.

Lymphoma

 

 

Non-neoplastic masses and cysts of testis

 

Testicular spermatocele and spermatic granuloma

A spermatocele is a cavity filled with spermatozoa. Small spermatoceles are dilated tubules such as the straight seminiferous tubule (also called the tubuli recti), or rete testis. Those cavities that are not lined by epithelium are where spermatozoa leak into the interstitium. These cavities quickly incite an inflammatory response and become spermatic granulomas. Spermatoceles and spermatic granulomas are unusual in the testis as a primary lesion as most are secondary to orchitis, needle biopsy or trauma.

 

Cysts of the testis

Cysts within the testis, lined by epithelium and with a central cavity filled with fluid, can be derived from the the rete testis, a network of ducts or from remnants of mesonephric tubules called the efferent ductules.mesonephric ductules have ciliated epithelium and this is a major differentiating factor.

 

Cystic rete testis

A cystic rete testis is different to other cysts in that it is a cystic dilation of the rete tubules secondary to obstruction of fluid outflow. It can be secondary to segmental aplasia of the mesonephric duct or spermatic granuloma of the epididymal head. Most cases would be missed or not deemed significant, especially if the primary lesion was identified. Typically, the mediastinum of the testis is affected so the testis has a large central cavity.

Some cases have dilation of the rete testis in one part only. Obstruction can be from lack of connection of the efferent ductules to the epididymis, fibrosis (Waters et al 2021) or other lesions.

 

Waters K, Schnuelle JG, Cofield LG, Rush J, Boakari Y, Cowley J, Horzmann K. Tubular ectasia of the rete testis in an Angus bull. Reprod Domest Anim. 2021; 56: 1261-1264.

Efferent ductule cyst

Cysts of the efferent ductules are true cysts, as they have an epithelial lining and a central cavity filled with fluid. These are different to cystic rete testis, a condition where there is cystic dilation of all of the rete testis from obstruction to outflow as would occur in segmental aplasia of the epididymis or spermatic granuloma of the epididymal head (see above).They are lined by ciliated epithelium, a distinguishing feature from a 'rete cyst'.

 

Rete testis cyst

 

Epidermoid cyst

 

 

 

 

 

Cystic interstitial cell tumour

One of the differential diagnoses of cystic rete testis is a rete cyst. Cystic interstitial cell tumour can, on rare occasions, be cystic and confused with a true cyst. Somewhere in the cystic cavity will be neoplastic cells. There will be no epithelium so if a cystic structure is found and histologically there is no epithelial wall, examination of the formalin fixed tissue will be necessary to identify the origin of the 'cyst' or, more correctly, the pseudocyst.

Parasites of the testis

 

 

 

 

Disease of the efferent ductules

The efferent ductules are the tubules that link the rete testis to the epididymal duct. Diseases, such as spermatic granuloma of the epididymal head, and cysts of the ducts are to be found under disease of the epididymis (non inflammatory) below.