Disease of the scrotal skin

 It has been often said that scrotal skin reacts just like the skin elsewhere, so it is not ‘special’. This is true, or at least is considered so. There is little point listing all the diseases of skin. Instead, the diseases that only affect scrotal skin, or have a predilectin for scrotal skin will be mentioned.

There is an extensive review of diseases of the scrotum (Cerundolo R, Maiolino P. 2002) and some of the conditions listed here are from that report.

Scrotal hyperplasia

The size of the scrotum of dogs is reported to increase in size, and become thickened with age. This thickening is reported to be hairless and to be deeply pigmented and wrinkled. Histologically the epithelium is hyperplastic and hyperkeratotic, and there is increased connective tissue (Bloom 1954).

Bloom F (1954). "Pathology of the Dog and Cat: The genitourinary system, with clinical considerations" Am. Vet. Publ Evanston, Illinois p258-259.

 

Masses (including neoplasms)

One may expect any neoplasm of skin to affect this region. Likewise, non neoplastic lesions would surely occur. Here are some examples of lesions that can occur

 

Diagnosis	Number
Mast cell tumour	30
Haemangioma/vascular hamartoma	23
Haemangiosarcoma	4
Soft tissue sarcoma	4
Benign melanoma/melanocytoma	3
Malignant melanoma	1
Leiomyoma	2
Sebaceous carcinoma	2
Squamous cell carcinoma	1
Fibroadnexal hamartoma	2
Infundibular cysts	1
Skin tag	2

Mast cell tumour

Mast cell tumours are very common on the scrotum. There is a general belief that they are more aggressive than elsewhere. Recent work by Sfiligoi et al (2005) suggests this is not the case.

Sfiligoi G, Rassnick KM, Scarlett JM, Northrup NC, Gieger TL. (2005) Outcome of dogs with mast cell tumors in the inguinal or perineal region versus other cutaneous locations: 124 cases (1990-2001). J Am Vet Med Assoc. 226(8):1368-1374.

Haemangioma/vascular hamartoma/hemangiomatosis

Weipers and Jarret (1954) report on hemangiomas of the scrotum. They begin as pigmented areas that remain static, but some progress to a small plaque that may eventually ulcerate and hemorrhage. Histologically they are cavernous haemangiomas. Bloom(1954) describes scrotal varicoses in the dog that have a similar description.

 

Bloom F (1954). "Pathology of the Dog and Cat: The genitourinary system, with clinical considerations" Am. Vet. Publ Evanston, Illinois p 259-260

Weipers WL, Jarret WFH. (1954) Haemangioma of the scrotum of dogs. Vet Rec 66: 106-108.

Leiomyoma

As anticipated, the numerous bundles of smooth muscle in the scrotal dermis will lead to the formation of neoplasia here.

 

Scrotal dermatitis and non neoplastic disease

Physicochemical injury

Self trauma (mutilation)

Involvement of the scrotal skin can be secondary to intrascrotal disease, especially of the tunics (see below) and periorchitis. Dogs with epididymitis can and will excessively lick the scrotum to the extent that there is dehiscence of the testis through the deep ulcer. The presence of spermatic granulomas is a similar inciting factor (mutilation dt spermatic granulomas (Althouse et al 1993)

Trauma

Some dogs target the genital region when fighting and this cause severe injury, both to the scrotum and the scrotal contents.

Frostbite

Severe cold and freezing of the skin with frostbite would be expected in those individuals whose scrotum is exposed to the elements in regions of subzero temperatures.

Sunburn

Some dogs spend long lengths of time lying in the sun, and some do so lying on their backs, thus exposing the scrotum to direct sunlight. Actinic injury would the anticipated from this.

Algal infection

Protothecosis can involve the scrotum of the dog (Ginel et al 1997)..

Bacterial infection

Brucella canis, the causitive agent of canine brucellosis, causes epididymitis and self mutilation of the scrotum can result. As well, a pyogranulomatous dermatitis caused by B canis is reported (Dawkins et al 1982). Schoeb and Morton (1978) report on a dog that had an ulcer of the scrotum from which B canis was cultured.

 

Parasites

Myiasis

Infection of scrotal wounds with the larvae (maggots) of flies is anticipated. Screw- worm fly would be one such example.

Cuterebra emasculator infestation can involve the scrotum.

Viruses and Ricketsias

Rocky Mountain spotted fever causes a vasculitis in dogs and this may involve the scrotum (Keenan et al 1977)

Reactive Histiocytosis

Moore (1984) lists the scrotum as a place particularly affected in dogs with systemic (reactive) histiocytosis. Palmeiro et al (2007) reports one case of scrotal involvement with reactive canine histiocytosis.

 

YagerBest Histovet cases

The Yager-Best Histovet database contains numerous diagnoses of scrotal dermatitis and a summary is provided below.

Table 1. Diagnosis of non neoplastic/nonproliferative scrotal disease

Diagnosis	Number
Traumatic/pyotraumatic	10
Contact dermatitis	5
Edema	3
Erythema multiforme	2
sterile pyogranuloma syndrome	1
Hematoma	1

 

Althouse GC, Evans LE, Hopkins SM. (1993) Episodic scrotal mutilation with concurrent bilateral sperm granuloma in a dog. J Am Vet Med Assoc 202(5):776-778.

Cerundolo R, Maiolino P. (2002) Review cutaneous lesions of the canine scrotum. Vet Dermatol. 13: 63-76.

Dawkins BG, Machotka SV, Suchmann D, McLaughlin RM.(1982) Pyogranulomatous dermatitis associated with Brucella canis infection in a dog. J Am Vet Med Assoc.181(11):1432-1433.

Ginel PJ, Perez J, Molleda JM, Lucena R, Mozos E. (1997) Cutaneous protothecosis in a dog.Vet Rec 140(25):651-653.

Keenan KP, Buhles WC Jr, Huxsoll DL, Williams RG, Hildebrandt PK. (1977) Studies on the pathogenesis of Rickettsia rickettsii in the dog: clinical and clinicopathologic changes of experimental infection. Am J Vet Res.38(6):851-856

Moore PF. (1984) Systemic histiocytosis of Bernese mountain dogs. Vet Pathol. 21(6):554-63

Palmeiro BS, Morris DO, Goldschmidt MH, Mauldin EA. (2007) Cutaneous reactive histiocytosis in dogs: a retrospective evaluation of 32 cases Veterinary Dermatology 18 (5), 332-340.

Schoeb TR, Morton R(1978) Scrotal and testical changes in canine brucellosis: a case report.J Am Vet Med Assoc. 172(5):598-600.

 

Vaginal tunics (tunica vaginalis) and testicular capsule (tunica albuginea)

The tunics are continuous with the peritoneum, so they are affected by the same influences as the abdominal cavity. Disease of the tunics can originate from the abdomen, or from the scrotal sac itself.

Fluid accumulation

Hematocele

Hydrocele

Parasitism

Zeman et al (1988) report a dog that developed scrotal cestodiasis from infection with Mesocestoides sp. The dog had severe peritoneal cestodiasis that migrated to the scrotal cavity.

Bloom (1954) reports the infection of the scrotum of a dog with Cuterebra emasculator. He also reports scrotal myiasis in dogs.

Bloom F (1954) Pathology of the dog and cat - The genitourinary system, with clinical considerations. American Veterinary Publications, Inc, Evanston Illinois. p261.

Scrotal (inguinal) hernia

Herniation of abdominal contents through the inguinal ring cause a swelling or mass in the region of the spermatic cord. This occurs as a result of trauma (such as when the abdomen of the dog is run over by a vehicle. It is reported as a spontaneous event (Dorn 1978) - omental fat herniated through the inguinal ring and occluded the vessels of the spermatic cord.

Hayes et al (1985) reported 235 dogs with inguinal hernias. 24 could have been trauma related. Waters et al (1993) reported on 35 dogs with inguinal hernias of which 11 were males. The herniated tissue is often fat, but intestines can sometimes be trapped in the hernia.

Inflammation (periorchitis)

Periorchitis is inflammation around the testis and it involves the tunics. It can arise from extension of peritonitis, from penetrating injury to the scrotum, but most commonly, it arises from epididymitis. The dependent nature of the scrotal sac means that exudates tend to remain in the sac. Organisation and fibrosis of exudates, and granulation tissue formation leads to adhesions.

Allison N, McDonald RK, Guist SR, Bentinck-Smith J. (1989) Eumycotic mycetoma caused by Pseudallescheria boydii in a dog. J Am Vet Med Assoc. 194(6):797-799

Neoplasia

There are an infinite number of potential neoplasms that could possibly be found on the vaginal tunics, or extending into the cavity. Neoplasia is very rare, however.

Carcinomatosis

There is one case of metastatic carcinoma of the vaginal tunics in the Yager-Best Histovet database (YB162821). The dog was a 10 year old Labrador. The appearance of the cells and the history suggested it may have been a transitional cell carcinoma. The neoplasm involved the tunics around the spermatic cord predominantly.

Figure 1: Carcinomatosis of vaginal tunics. There are multifocal coalescing white nodules over the vaginal tunics.

Leiomyoma

Patnaik and Liu (1975) reported on a leiomyoma of the vaginal tunic in a 13 yr old dog. It was reported to be benign. McEntee (1990) also reports seeing one case.

McEntee K (1990) Reproductive Pathology of Domestic Mammals. Academic Press p 298

Patnaik AK, Liu SK.Leiomyoma of the tunica vaginalis in a dog. Cornell Vet. 1975 Apr;65(2):228-31.

Mesothelioma

Cihak et al (1986) found a 13 year old dog with a mesothelioma of the vaginal tunic - it spread to the peritoneum.

Vascellari et al (2011) reports on a case of malignant mesothelioma of the left vaginal tunics in a dog. This dog also had nodules within the peritoneum and the mesentery. This mesothelialoma was in a reactive for cytokeratin (AE1/AE3), vimentin and HBME-1 (a mesothelial marker).

There are two mesotheliomas of the tunic in the Yager-Best Histovet database (YB10166, 144539). One was a 10 year old Bouvier and the other was a 6 year old Staffordshire terrier. There was no followup on either dog.

McEntee (1990) reports seeing 4 mesotheliomas of the tunics.

Figure :Mesothelioma of the vaginal tunics (YB144539)

Sarcoma

There is one case of fibrosarcoma involving the vaginal tunic in the Yager-Best Histovet database (YB162010). No followup is available to provide the clinical outcome.

Figure 2: Fibrosarcoma of vaginal tunic.

Cihak RW, Roen DR, Klaassen J. (1986) Malignant mesothelioma of the tunica vaginalis in a dog. J Comp Pathol. 96(4):459-462.

Bloom F (1954) "Pathology of the Dog and Cat: The Genitourinary System, with clinical considerations" Amer Vet Publ Evanston, Illinois. p

Dorn AS. (1978) Spermatic cord occlusion in a dog.J Am Vet Med Assoc. 173(1):81

Hayes HM, Wilson GP, Pendergrass TW, Cox VS. (1985) Canine cryptorchidism and subsequent testicular neoplasia: case control study with epidemiologic update. Teratology 32: 51-56.

McEntee K (1990) Reproductive Pathology of Domestic Mammals. Academic press. p297.

McNeil PE, Weaver AD. (1980) Massive scrotal swelling in two unusual cases of canine Sertoli cell tumour. Vet Rec 106: 144-146.

Patnaik AK, Liu SK. (1975) Leiomyoma of the tunica vaginalis in a dog. Cornell Vet. 65(2):228-31.

Vascellari M, Carminato A, Camali G, Melchiotti E, Mutinelli F. (2011) Malignant mesothelioma of the tunica vaginalis testis in a dog: histological and immunohistochemical characterization J Vet Diagn Invest 2011, 23:135–139

Waters DJ, Roy RG, Stone EA. (1993) A retrospective study of inguinal hernia in 35 dogs.Vet Surg. 22(1):44-49

Zeman DH, Cheney JM, Waldrup KA.1988 Scrotal cestodiasis in a dog. Cornell Vet 78(3):273-279.