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Home , Leydig cell tumour, Sertoli cell tumour

EQUINE VETERINARY EDUCATION / AE / april 2009 177

Clinical Commentary Equine testicular tumours B. A. Valentine Veterinary Diagnostic Laboratory and Department of Biomedical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, Oregon 97331, USA.

In this issue Weiermayer and Richter (2009) describe a been reported in the donkey (Galofaro et al. 2007) and in stallion with both a and a leiomyoma involving a zebra x mare (Pandolfi and Roperto 1983). the testes. Reports of testicular neoplasia in horses are Testicular neoplasia can be divided into tumours of limited, undoubtedly related to the early age of germ cell origin, tumours of interstitial and stromal cells, and castration of most equids (Schumacher 1999), and are tumours of other cell origin (Fig 1; Cooper and Valentine most often of single case reports. Accurate information 2002; MacLachlan and Kennedy 2002). The most common regarding the general types and behaviour of testicular tumours of germ cell origin in the horse are seminoma and neoplasia in the horse requires a broad literature review, . Cystic teratoma is also called testicular dermoid bearing in mind that certain tumour types that are cyst. Other germ cell tumours in the horse are apparently inherently newsworthy, such as and tumours rare, highly aggressive malignant tumours. Tumours of sex- with widespread metastases, may be overrepresented. cord stromal origin include Leydig (interstitial) cell tumour, Most reports are in horses and ponies (Willis and Ruddock Sertoli (sustentacular) cell tumour, and the occasional 1943; Becht et al. 1979; Smyth 1979; Stick 1980; Rahaley tumour exhibiting mixed differentiation, either confined to et al. 1983; Gibson 1984; Trigo et al. 1984; Shaw and Roth sex-cord stromal elements or combined with germ cell 1986; Valentine and Weinstock 1986; Cullen et al. 1987; elements. Tumours of other cell types, most often smooth Gelberg and McEntee 1987; Johnson and Steinberg 1989; muscle or lymphoma, are also possible (Held et al. 1992; Smith et al. 1989; Hunt et al. 1990; Held et al. 1992; Hay Allison and Moeller 1999; Cooper and Valentine 2002). et al. 1997; Duncan 1998; Veeramachaneni and Sawyer An attempt to summarise the reported testicular 1998; May et al. 1999; Beck et al. 2001; Pollock et al. 2002; tumours in the horse, excluding lymphoma and smooth Pratt et al. 2003; Zanghi 2004; Ball et al. 2007; Melo et al. muscle tumours but including the seminoma in the report 2007; Edwards 2008), but testicular neoplasia has also by Weiermayer and Richter (2009), is presented in Table 1. Review of these data suggests the following: Equine testicular tumours 1) Testicular tumours occur in young and in old horses. 2) Neoplasia occurs in both cryptorchid and descended Germ cell Sex-cord stromal cell Other testes. Seminoma Leydig (interstitial) cell Leiomyoma/ Teratoma Sertoli (sustentacular) cell 3) Malignant testicular neoplasia is relatively common in Teratocarcinoma Mixed sex-cord/stromal Lymphoma the horse. In fact, the range and behaviour of testicular tumours in Mixed germ cell/sex-cord/stromal the horse more closely resembles those of testicular Fig 1: Classification of equine testicular tumours. neoplasia in man (Young 2008) than of the dog

TABLE 1: Summary of published equine testicular tumours

Mean age Age range Tumour type Total (years) (years) Malignant Cryptorchid

Seminoma 16 16.5 11–22 6 5 Interstitial cell 12 9 3–15 0 9 Teratoma/dermoid cyst 12 2 0*–5 0 5 Sertoli/mixed germ cell/sex-cord 6 17 10–30 3 1 Teratocarcinoma/embryonal carcinoma 2 4 1.5–7 2 1

* 3-day-old foal 178 EQUINE VETERINARY EDUCATION / AE / april 2009

(MacLachlan and Kennedy 2002), the animal species in Held, J.P., McCracken, M.D., Toal, R. and Latimer, F. (1992) Epididymal which testicular neoplasia are most commonly recognised. swelling attributable to generalized lymphosarcoma in a stallion. J. Am. vet. med. Ass. 201, 1913-1915. The majority of canine testicular tumours are benign Hunt, R.J., Hay, W., Collatos, C. and Welles, E. (1990) Testicular (MacLachlan and Kennedy 2002), but this appears to be an seminoma associated with torsion of the spermatic cord in two exception within the animal kingdom rather than the rule. cryptorchid stallions. J. Am. vet. med. Ass. 197, 1484-1486. Although a true incidence of equine testicular neoplasia Johnson, R.D. and Steinberg, H. (1989) Leiomyoma of the tunica has yet to be determined, the relatively large number of albuginea in a horse. J. comp. Pathol. 100, 465-468. reports of equine testicular neoplasia compared to the MacLachlan, N.J. and Kennedy, P.C. (2002) Tumors of the genital relatively small number of male horses not castrated at an systems. In: Tumors in Domestic Animals, 4th edn., Ed: D.J. Meuten, Iowa State Press, Ames. pp 561-567. early age suggests that testicular neoplasia are not at all May, K.A., Moll, H.D., Duncan, R.B, Pleasant, R.S. and Purswell, B.J. uncommon in the horse. The results of this recent literature (1999) Unilateral tumour resulting in acute colic and review support the conclusions of Brinsko (1998) that scrotal swelling in a stallion with descended testes. Equine vet. J. 31, testicular tumours in the horse may be more common than 343-345. previously thought. Submission of equine testicular tumours Melo, C.M., Papa, F.O., Prestes, N.C., Alvarenga, M.A. and Laufer- Amorim, R. (2007) Bilateral in a stallion. J. equine for histopathological diagnosis, and continued reporting of vet. Sci. 27, 450-453. equine testicular tumours, and particularly of the outcome Pandolfi, F. and Roperto, F. (1983) Seminoma with multiple metastases of equine testicular tumours, will be vital to provide the in a zebra (Equus zebra) X mare (Equus caballus). Equine vet. J. 15, necessary database to understand the incidence and 70-72. behaviour of testicular neoplasia in the horse. Pollock, P.J., Prendergast, M., Callanan, J.J. and Skelly, C. (2002) Testicular teratoma in a three-day-old Thoroughbred foal. Vet. Rec. References 150, 348-350. Pratt, S.M., Stacy, B.A., Whitcomb, M.B., Vidal, J.D., De Cock, H.E. and Wilson, W.D. (2003) Malignant tumor in the retained Allison, N. and Moeller, R.B. (1999) Bilateral testicular leiomyosarcoma in abdominal testis of a unilaterally cryptorchid horse. J. Am. vet. med. a stallion. J. vet. diag. Invest. 11, 179-182. Ass. 222, 486-490. Ball, B.A., Conley, A.J., Grundy, S.A., Sabeur, K. and Liu, I.K.M. (2007) Rahaley, R.S., Gordon, B.J., Leiopold, H.W. and Peter, J.E. (1983) Sertoli Expression of anti-Müllerian hormone (AMH) in the equine testis. cell tumour in a horse. Equine vet. J. 15, 68-70. Theriogenol. 69, 624-631. Shaw, D.P. and Roth, J.E. (1986) Testicular teratocarcinoma in a horse. Becht, J.L, Thacker, H.L. and Page, E.H. (1979) Malignant seminoma in a Vet. Pathol. 23, 327-328. stallion. J. Am. vet. med. Ass. 175, 292-293. Schumacher, J. (1999) Testicular neoplasia of horses: an underreported Beck, C., Charles, J.A. and Maclean, A.A. (2001) Ultrasound condition. Equine vet. J. 31, 270-272. appearance of an equine testicular seminoma. Vet. Radiol. Ultrasound 42, 355-357. Smith, B.L., Morton, L.D., Watkins, J.P., Taylor, T.S. and Storts, R.W. (1989) Malignant seminoma in a cryptorchid stallion. J. Am. vet. med. Ass. Brinsko, S.P. (1998) Neoplasia of the male reproductive tract. Vet. Clin. 195, 775-776. N. Am.: Equine Pract. 14, 517-533. Smyth, G.B. (1979) Testicular teratome in an equine cryptorchid. 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