Testicular cancer (TC) is the most common cancer affecting men between the ages of 15 and 35. When a mass is suspected through a physical exam, a scrotal ultrasound is the initial imaging study performed to investigate the cause. Ultrasound provides high-resolution images of the testicle and surrounding structures. It quickly helps determine if a mass is located inside or outside the testicle and distinguishes between solid, fluid-filled, or mixed-composition lesions. This imaging technique serves as the primary tool to confirm the presence of an abnormal growth and to guide the necessary next steps for diagnosis and treatment.
Understanding the Ultrasound Image
Ultrasound technology uses high-frequency sound waves that travel into the body and bounce back after encountering different tissues. The returning echoes are then mapped onto a screen as shades of gray, a process called grayscale mapping. Denser tissues reflect more sound waves and appear bright, or hyperechoic. Less dense or fluid-filled areas reflect fewer waves and appear darker, or hypoechoic, which is sometimes described as anechoic if completely black. A normal, healthy testicle exhibits a medium-level, uniform, and slightly grainy texture, known as homogeneous echogenicity.
Key Visual Indicators of Malignancy
Malignant tumors almost always originate within the testicle itself, presenting as a solid mass within the testicular parenchyma. The typical appearance of a cancerous mass, particularly the common germ cell tumors, is a region that is darker than the surrounding normal tissue, known as a hypoechoic mass.
Tumors frequently display internal heterogeneity, meaning the mass has a mixed echo pattern with various shades of gray within it. This mixed appearance is often due to areas of hemorrhage, necrosis, or internal cystic change within the rapidly growing cancer. Nonseminomatous germ cell tumors, in particular, commonly exhibit this solid and cystic multicomponent appearance.
The borders of a malignant mass are sometimes irregular or poorly defined, contrasting with the smooth, distinct margins often seen in benign lesions. Color Doppler ultrasound evaluates blood flow within the mass. Malignant tumors often demonstrate increased blood flow, or hypervascularity, compared to the normal testicular tissue surrounding it.
The increased vascularity occurs because the tumor creates new blood vessels to support its rapid growth. However, the absence of this increased blood flow does not automatically rule out cancer. Some tumors, such as seminomas, may present as a more uniformly hypoechoic and homogeneous mass.
When Findings Are Not Cancer
Many conditions can cause a palpable mass or pain, leading to an ultrasound, yet are found to be non-cancerous. Most masses found outside the testicle, referred to as extratesticular masses, are benign and do not require the same immediate action as an intratesticular solid mass.
Common fluid collections include a hydrocele, which is a simple collection of anechoic fluid between the layers surrounding the testicle. Spermatoceles, which are cysts in the epididymis, also appear anechoic and are typically filled with tiny internal echoes representing cellular debris.
Benign masses often have visual characteristics that help distinguish them from malignancy, such as well-defined, smooth borders. For example, an epidermoid cyst is a benign solid-appearing mass that can have a characteristic “onion-ring” pattern.
Epididymitis, which is inflammation of the epididymis, can cause swelling and pain. The ultrasound may show an enlarged epididymis with increased blood flow on Doppler, but the testicle itself remains normal. Testicular microlithiasis involves multiple tiny calcifications inside the testicle. It is often found incidentally and usually requires only surveillance if no solid mass is present.
Steps After a Suspicious Scan
The finding of a solid, suspicious intratesticular mass on ultrasound requires immediate and standardized follow-up to confirm the diagnosis and determine the extent of disease. The next step involves a prompt referral to a specialist, such as a urologist.
Tumor Markers and Blood Tests
Before any surgical intervention, blood tests are mandatory to check for specific tumor markers. These blood markers include alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), and lactate dehydrogenase (LDH). These proteins can be elevated in the presence of testicular cancer and are important for both diagnosis and for establishing a baseline for monitoring the patient after treatment.
Definitive Diagnosis and Staging
The definitive diagnostic and therapeutic step for a highly suspicious mass is a radical inguinal orchiectomy, the surgical removal of the affected testicle through an incision in the groin. A simple needle biopsy is avoided because of the risk of spreading the cancer cells or altering the lymphatic drainage pathways. Once the testicle is removed, the tissue is examined by a pathologist to confirm the cancer type and guide further treatment decisions. Additional imaging, such as a CT scan of the chest, abdomen, and pelvis, is performed after the orchiectomy to determine if the cancer has spread (staging the disease).