Neoplastic and non-neoplastic testicular lesions in dogs: Color Doppler imaging, histological and immunohistochemical study of the canine testicular disease

Testicular tumors are one of the most common neoplasms of male dogs, accounting for 90% of all tumors of the genitourinary tract. Interstitial Cell Tumors (ICT), Sertoli Cell Tumors (SCT) and seminomas are the most frequently detected. The risk factors implicated in the development of the neoplastic process involving testes are numerous. Their prevalence has been evaluated several times and in different time frame by authors. The outcomes vary widely. The reason behind the variability of the results is mainly related to the characteristics of the study group analysed. The prevalence of testicular cancer in the canine population is unclear, but the risk factors are commonly accepted by authors. Age, congenital conditions as cryptorchidism, breed and environment play a major role in the carcinogenesis of this type of tumors. Although many patients present clinical symptoms of the testicular disease, most canine primary tumors are incidental findings. The use of color Doppler ultrasound has become more and more important for the diagnosis of reproductive diseases in dogs. Color flow imaging has made ultrasound the modality of choice for the evaluation of the vascularization of the testes but its role in the characterization of the neoplastic lesions has not yet been defined. Intratesticular flow patterns change in course of pathological conditions of the testis. The ability to evaluate low blood flows can add valuable information to the diagnostic workup, improving the accuracy of ultrasound. The aim of the present study is to assess the potential of color Doppler ultrasound to differentiate neoplastic and non-neoplastic testicular lesions in dogs through the evaluation of specific vascular flows parameters. Sixty-four male dogs of various breed, aged between 7 and 15 years affected by testicular disorders were selected. B-mode and color Doppler ultrasound examinations were carried out. Blood flow characteristics of the areas of interest were assessed through the evaluation of Resistive Index (RI), Pulsatility Index (PI) and Vascularity Index. All subjects underwent bilateral orchiectomy before submitting testes for histolopathological evaluations. Immunohistochemistry for CD31 on neoplastic nodules was carried out for the evaluation of the microvessel density within the lesion. The 78% of the lesions examined resulted to be neoplastic at the histological evaluation. Conventional B-mode US was able to detect the presence of all the lesions, but not accurate to assess margins in lesions at early stage. The sonographic appearance was not specific of the tumor type. At the color Doppler examination, all tumors showed increased vascularity into and around their bounds. Vascular flow signals were significantly intensified around and into the neoplastic lesions and significantly higher than non-neoplastic conditions, such as inflammatory and degenerative processes, fibrosis, necrosis and cysts. VI markedly increased in solid tumors. The variation of the RI in course of neoplastic, inflammatory and degenerative conditions was not significantly relevant. The sonographic evidences have been supported by immunohistochemistry. Based on our results and on the understanding that the diagnosis of testicular tumors is dependent upon histological examination, the information on vascular patterns of testicular lesions provided by color Doppler ultrasound may be a strong valuable tool for the assumption of the diagnostic opinion and may be considered one of the most reliable line of investigation of the canine testicular disease.