Role and Limitations of Conventional Ultrasonography in Canine Testicular Tumors

Testicular tumors are the most common neoplasms affecting the male canine reproductive system, with prevalence ranging widely from 2% to 60%, and a clear association with advancing age. Among these, seminomas, Sertoli cell tumors, and Leydig cell tumors are the most frequently encountered histological types¹. Despite their frequency, early diagnosis remains a challenge, especially when fertility preservation is a concern in breeding dogs. 

Role of Conventional Ultrasonography in Detection 

For decades, two-dimensional (2D) ultrasonography has served as the primary imaging modality for evaluating the male reproductive tract in both human and veterinary practice¹. Its utility lies in its ability to reliably detect testicular abnormalities in a non-invasive manner. In the present study, B-mode ultrasonography successfully identified testicular tumors in nearly all cases, with only one Sertolioma being missed. 

However, detection alone is not sufficient. Clinically, the need extends beyond identifying a lesion to understanding its nature and potential behavior. 

Why Characterization Remains a Challenge¹ 

A major limitation of conventional ultrasonography is its inability to differentiate between tumor types. The ultrasonographic appearance of testicular tumors is highly variable, with no consistent features that allow reliable classification. Lesions may appear focal or diffuse, and their size, margins, and echogenicity vary significantly. 

In this study, most lesions were predominantly hypoechoic, but this feature was not specific to any tumor type. Similarly, both focal and diffuse patterns were observed without a clear correlation to histological diagnosis. This variability makes it difficult to distinguish between seminomas, Sertoliomas, and Leydig cell tumors based on grayscale imaging alone. 

Overlap with Non-Neoplastic Conditions 

Another important limitation is the overlap between neoplastic and non-neoplastic conditions. While ultrasonography can help differentiate tumors from conditions such as orchitis, torsion, or epididymitis, it cannot reliably identify the specific tumor type^1,2. This creates a diagnostic gray zone, where further characterization becomes necessary. 

Clinical Implications of Limited Specificity 

The inability to characterize tumors has direct clinical consequences. Without clear differentiation, clinicians may be unable to determine the biological behavior of the lesion or its potential impact on fertility. This is particularly relevant in stud dogs, where preserving reproductive function is a priority. 

Additionally, although metastasis is less common in dogs compared to humans, early diagnosis still plays a role in reducing associated risks³. Therefore, relying solely on conventional ultrasonography may delay optimal clinical decision-making. 

Need for Advanced Imaging Approaches 

Given these limitations, there has been a growing interest in incorporating advanced imaging techniques that provide functional information in addition to structural details. Conventional ultrasonography offers a static view of the lesion, but does not capture dynamic processes such as blood flow and vascular architecture. 

Since tumor vascularization reflects angiogenesis, which is linked to tumor growth and malignancy, assessing blood flow becomes clinically relevant¹. This has led to the exploration of Doppler-based techniques and contrast-enhanced imaging as adjuncts to conventional ultrasound. 

Conclusion 

While 2D ultrasonography remains an essential first-line tool for detecting testicular tumors in dogs, its limitations in characterization cannot be overlooked. The highly variable and non-specific imaging features restrict its diagnostic accuracy when used alone. As a result, there is a clear need for complementary imaging modalities that can provide additional insights into tumor vascularity and behavior. A shift from purely structural assessment to a more comprehensive evaluation is critical for improving diagnostic precision and guiding clinical management. 

Reference 

1. Orlandi R, Vallesi E, Boiti C, Polisca A, Bargellini P, Troisi A. Characterization of testicular tumor lesions in dogs by different ultrasound techniques. Animals. 2022 Jan 17;12(2):210. https://doi.org/10.3390/ani12020210 

2. de Souza MB, da Silva LD, Moxon R, Russo M, England GC. Ultrasonography of the prostate gland and testes in dogs. In Practice. 2017 Jan;39(1):21-32. https://www.iris.unina.it/retrieve/handle/11588/845352/415529/In%20Practice-2016-de%20Souza-Prostate%20and%20Testes%20Ultrasound.pdf 

3. Nascimento HH, Santos AD, Prante AL, Lamego EC, Tondo LA, Flores MM, Fighera RA, Kommers GD. Testicular tumors in 190 dogs: clinical, macroscopic and histopathological aspects. Pesquisa Veterinária Brasileira. 2020 Jul;40(7):525-35. https://www.scielo.br/j/pvb/a/RXCDQJzbjSbrZGYX3xY99Yf/?format=pdf&lang=en