114
EQUINE VETERINARY EDUCATION / AE / MARCH 2015
Fig 2: Histopathological appearance of a leiomyoma of the tunica albuginea of the testis of a horse, ×100, haematoxylin and eosin.
Fig 1: Gross appearance of testes from a 19-year-old horse with bilateral testicular swelling.
The testes, excluding the masses, measured 12 cm in
length and 6 cm in diameter. Gross examination revealed firm, white, nodular masses on the surface of both testes. They were overlying the testicular parenchyma, positioned close to, but not involving the head of the epididymis and pampiniform plexus. They were varying in size, the largest, attached to the left testicle, measuring 10 cm in length and 6 cm in diameter. Sectioning the testes demonstrated multiple nodular masses, with underlying testicular parenchyma of unremarkable appearance. The cut surface of individual masses had a dense, whorling, fibrous, white and somewhat shiny appearance (Fig 1). Histopathological examination of the testes revealed well
demarcated, densely cellular, nodular, expansile, encapsulated neoplastic masses arising from the tunica albuginea. The neoplastic cells were arranged in broad, closely packed, disorientated fascicles surrounded by a fine fibrovascular stroma (Fig 2). The neoplastic cells were spindle-shaped, with a moderate amount of sometimes vacuolated eosinophilic cytoplasm and had indistinct cell borders. The nuclear to cytoplasmic ratio was low. The elongated nuclei were centrally placed, with finely stippled, vesicular chromatin and had individual inconspicuous nucleoli. Anisocytosis and anisokaryosis were mild. No mitotic figures were observed in 10 high power (×400) fields. Staining with a mouse anti-human monoclonal antibody reactive to alpha smooth muscle actin (Novocastra NCL-SMA) confirmed the smooth muscle origin of the cells (Skalli et al. 1986), supporting a diagnosis of bilateral leiomyoma (Fig 3).
© 2014 EVJ Ltd
Fig 3: a) Immunohistochemistry of a leiomyoma of the tunica albuginea of the testis of a horse, ×200, smooth muscle actin. b) Positive control. c) Negative control.
Follow-up was performed 6 months post surgery by
telephone conversation with the horse’s owner. The horse was reported to be clinically well, had recovered routinely from surgery and was disease-free.
Discussion
In the case reported here, histopathological examination was consistent with a bilateral, multicentric, well differentiated leiomyoma of the tunica albuginea. Leiomyomas are tumours of smooth muscle origin and testicular leiomyomas have been reported in a number of species, including sheep, horses and man (Foster et al. 1989; Johnson and Steinberg 1989; Chiong et al. 2004). They are discrete, expansile, noninvasive tumours and, when well differentiated, can be difficult to distinguish from normal smooth muscle. However, the presence of a nodular mass with some degree of disorientation of the cells characterises these masses as tumours (Cooper and Valentine
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88
