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History

A 7-year-old, male common mynah (Acridotheres tristis) was examined because of a 2-week history of decreased appetite, lethargy, emaciation, difficulty in grasping the perch, abdominal enlargement, decreased mimicry and singing, and inability to maintain normal posture. The bird was kept in a cage by itself and fed a diet that consisted of baked pasta and rice supplemented with occasional fruits and vegetables. The patient had no history of previous illness. On physical examination, the bird was bright, alert, and responsive; was in moderate body condition; and weighed 95 g. When examined, the bird was dyspneic, and coelomic palpation revealed a firm tissue mass in the abdominal region. Radiography and ultrasonography examinations were recommended for further diagnostic evaluation of the coelomic mass. The radiographic images revealed a spheroid mass of soft tissue opacity. On evaluation of the radiographic images, the mass origin was not detectable in the coelomic cavity, although the liver appeared displaced dorsally (lateral view) and cranially (ventrodorsal view) (Fig 1). Ultrasonography with a linear (7-12 MHz) transducer was performed to further evaluate the tissue mass. The ultrasonographic appearance of the mass was spheroid and was surrounded by an echogenic capsule (Fig 2). The mass parenchyma was homogenic and hypoechoic and was determined to have an increased blood flow by Doppler assessment. However, the origin of the mass was not evident.

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

Diagnosis

Although surgical treatment was offered, the bird was euthanatized at the owner's request. The necropsy examination revealed a white, firm, subspherical mass with a smooth surface, measuring 3 cm x 3.5 cm x 3 cm. The mass was located in the left side of coelomic cavity, attached to the left ventrolateral border of the left kidney. The mass, believed to be the testicle, had microlobulated structures on its cut surface. The spleen measured 4 cm x 1 cm x 1 cm, was red-colored and irregular, and was located on the right side of abdominal cavity adjacent to the mesenteric root. The spleen was mottled and had raised, pale, cream-white surface nodules. The gastrointestinal tract and liver appeared to be normal in shape and color, although they were displaced because of compression.

Histopathologic examination of the tissue samples obtained from the testicle revealed closely packed, oval to elongated cells arranged either in diffuse sheets, cords, and nests or in groups surrounded by either delicate or thick, fibrous tissue stroma in small or large disorganized, lumen-like constituents, which were similar to preexisting tubular structures. The neoplastic cells had scant to moderate cytoplasm and poor- to well-defined boundaries. The round or oval vesicular nuclei were relatively uniform in appearance. In almost all the nuclei, within the tissue sections examined, were 1 or 2 prominent nucleoli. Weakly eosinophilic, amorphous colloidal material was found either freely within the stroma or lumen or lined by a single layer of neoplastic cells (Figs 3 and 4). The red pulp of spleen was replaced by a proliferation of lymphoid cells and a high concentration of neoplastic cells resembling the germ tumor cells found in the testis.

[FIGURE 3 OMITTED]

[FIGURE 4 OMITTED]

On immunohistochemical staining, the tumor cells stained intensely and diffusely for calretinin (Fig 5), whereas there was no reaction for placental alkaline phosphatase and c-Kit expression. Neither the germinal epithelium nor sex-cord stromal elements (Sertoli and Leydig cells) of normal testicular tissues (chicken) revealed any immunoreactivity to any of the markers used to evaluate the mynah tissue. Furthermore, the neoplastic cells failed to react with histochemical stain, although the colloidal substances appeared pale. The histopathologic diagnosis in this bird was a Sertoli cell tumor with splenic metastasis. In a previous case, a Sertoli cell tumor was diagnosed in a pigeon (Columba livia) on histopathologic examination. (1) To compare findings of the present mynah case with those of the pigeon with the Sertoli cell tumor, the immunohistochemistry panel was used in the testicular tissue samples of that pigeon. In the pigeon case, only a few (3%-5%) neoplastic cells had conspicuous positive staining for calretinin; however, similar to findings in the common mynah case, results were negative for placental alkaline phosphatase or c-Kit expression.

[FIGURE 5 OMITTED]

Discussion

In captive and free-ranging birds, the occurrence of testicular tumors has been reported to be 3 times more common than ovarian and oviductal neoplasms. The inoculation against subgroup J avian leukosis virus may have a potential role in the development of testicular tumors in birds. (3) To our knowledge, this is the first report of a Sertoli cell tumor in a common mynah.

Both interstitial and Sertoli cells in normal canine testicular tissue may express calretinin in their cytoplasms and nuclei, whereas the germ cells show no reaction to this marker. Calretinin is considered a specific and reliable marker for differentiation of sex cord-stromal tumors in humans, but its expression is demonstrated in all types of canine testicular neoplasms, including germ cells tumor (seminoma) and sex cord-stromal tumors (Sertoli cell and Leydig cell tumors). (4) As opposed to the neoplastic cell reaction in the avian cases, the normal germ cells of testicles of control chickens, like human testicular tissue, are negative for calretinin. Therefore, this marker may be upregulated only for primordial or neoplastic germ cells with lesser degrees of differentiation and high proliferation rates, but not for cells in developmental phases of maturation. Normal Leydig cells and spermatogonia of canine testicles express c-Kit in their cytoplasm, and canine Leydig cell tumors express positive immunolabeling for c-Kit, whereas c-Kit labeling is negative for Sertoli cell tumors. (5) The findings in this case demonstrate that immunohistochemistry may be a reliable method to designate the types of avian testicular tumors, especially those that are poorly differentiated.

This case was submitted by Omid Dezfoulian, DVM, PhD, Mehdi Cheraghchibashi, DVM, and Seyed Mostafa Peighambari, DVM, MSc, PhD, from the Department of Pathobiology, School of Veterinary Medicine, Lorestan University, Khorramabad, Iran (Dezfoulian); and the Department of Avian Diseases, Faculty of Veterinary Medicine, University of Tehran. Tehran, Iran (Cheraghchibashi, Peighambari).

At this time, evaluate the case history, physical examination findings, and Figures 1-2, and formulate a differential diagnosis list card treatment plan.

References

(1.) Razmyar J, Dezfoulian O, Shojadoost B, et al. Sertoli cell tumor in a pigeon (Columba livia). J Avian Med Surg. 2005;19(4):286-288.

(2.) Latimer KS. Oncology. In: Ritchie BW, Harrison GJ, Harrison LR, eds. Avian Medicine: Principles and Application. Lake Worth, FL: Wingers Publishing; 1994:642-648.

(3.) Payne LN, Venugopal K. Neoplastic diseases: Marek's disease, avian leukosis and reticuloendotheliosis. Rev Sci Tech. 2000;19(2):544-564.

(4.) Radi ZA, Miller DL. Immunohistochemical expression of calretinin in canine testicular tumours and normal canine testicular tissue. Res Vet Sci. 2005;79(2):125-129.

(5.) Grieco V, Banco B, Giudice C, et al. Immunohistochemical expression of the KIT protein (CD117) in normal and neoplastic canine testes. J Comp Pathol. 2010;142(2-3):213-217.
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Publication:Journal of Avian Medicine and Surgery
Date:Jun 1, 2015
Words:1142
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