Intratesticular masses: malignant tumors
Malignant testicular neoplasms account for about 1% of all cancers in men, with a peak incidence between 15 and 45 years of age. In 95% of cases, these are germ cell tumors (germ cell tumours) originating from germ cells.
Sonographic characteristics depend on the histological type:
- Seminomas (seminomas): the most frequent type (peak in the 4th–5th decades). On ultrasound, they appear as well-circumscribed, uniform (homogeneous), and hypoechoic masses compared to the normal parenchyma. Extremely radiosensitive.
- Teratomas (teratomas): have mixed echogenicity, often containing cystic spaces and calcifications.
- Embryonal cell tumors: well-circumscribed, but less uniform than seminomas.
Color Doppler ultrasound (CDUS) often shows increased blood flow within the tumor; however, this sign is not strictly mandatory and does not allow for 100% accurate differentiation of cell types or distinction between neoplasia and a benign process.
Cystic extratesticular lesions
Cystic structures are much more common than solid ones and are benign in the vast majority of cases. A small amount of fluid around the testis is a normal variant.
- Hydrocele (hydrocele): the most common cause of a scrotal mass. It represents a fluid collection around the anterior and lateral surfaces of the testis. The content is usually anechoic, but may contain echoes/debris (cholesterol crystals). In infants, it occurs due to a patent processus vaginalis.
- Spermatocele and epididymal cysts: occur due to ductal dilation. Spermatocele is a retention cyst of the epididymal head containing sperm. Regular cysts do not contain sperm and can be located in any segment. On ultrasound, these are well-circumscribed structures with anechoic contents.
Inflammatory diseases and emergencies
Enlargement of the epididymis of any etiology causes extratesticular edema. The most common cause is acute epididymitis (acute epididymitis) caused by bacterial infection (including STIs).
On the sonogram, the epididymis (or just its head) is enlarged, and its echogenicity is decreased and heterogeneous. If the process spreads to the testis, orchitis develops. Color Doppler flow mapping is critically important here: inflammation produces a dramatic increase in blood flow, which helps rule out testicular torsion.
A formidable complication of epididymo-orchitis is pyocele (pyocele)—an accumulation of pus in the scrotum. On ultrasound, it appears as a multiloculated fluid collection with multiple low-level echoes. This is a urological emergency carrying the risk of Fournier's gangrene.
Non-focal anomalies and tumor "mimics"
Some benign conditions can visually resemble cancer, requiring careful evaluation to avoid unnecessary orchiectomy:
- Tubular ectasia of the rete testis: cystic dilatation of the tubules in older men. When in doubt, MRI is used—the lesions do not show contrast enhancement and are not visible on T2-weighted images.
- Testicular microlithiasis: calcium deposits in the convoluted seminiferous tubules. Ultrasound criterion: 5 or more hyperechoic foci (1–3 mm) without posterior acoustic shadowing.
- Splenogonadic fusion: a congenital anomaly (fusion of the splenic primordium and the gonadal ridge). In the discontinuous form, a solid mass is identified at the upper pole of the left testis. The diagnosis is confirmed by technetium-99m sulfur colloid scintigraphy.
Second-line methods and staging
If ultrasound capabilities are insufficient (e.g., in organized hematomas or testicular infarction), multiparametric MRI (including T1, T2, diffusion-weighted imaging, and contrast enhancement) is used as a second-line method.
For staging confirmed cancer, the gold standard is CT of the abdomen, pelvis, and chest. It is important to remember that lymphatic drainage from the testes is predictable: it goes not to the groin, but to the retroperitoneum at the level of the renal hila. 18F-FDG PET-CT is not used for primary staging, but is useful for assessing residual disease after chemotherapy.
Briefly: answers to topical questions
What complications of acute epididymo-orchitis can be detected on ultrasound?
Complications of acute infectious orchitis include abscess formation or the development of a purulent-necrotic process, while the outcome of inflammation can be fibrosis and scarring with disruption of the organ's architecture. In gonococcal epididymo-orchitis, abscesses form in the epididymis with marked destruction of adjacent tissues. Specific ultrasound signs of these complications are not detailed in the cited sources.
What ultrasound signs are characteristic of varicocele?
Varicocele is characterized by the presence of multiple dilated, tortuous tubular structures posterior to the testis.
- Vein diameter exceeds the threshold value > 2 mm (alternative criteria: 2.7 mm for subclinical and 3.6 mm for clinical varicocele).
- Localization — structures may extend to the lower pole of the testis.
- Blood flow — spontaneous blood flow may not be visualized; provocative maneuvers (coughing, quick inspiration, Valsalva maneuver) are effective for detecting it.
How does testicular rupture appear on ultrasound in scrotal trauma?
In testicular rupture, sonograms reveal ill-defined organ contours and heterogeneous parenchymal echogenicity.
- Contours become ill-defined due to rupture of the tunica albuginea (tunica albuginea) and extrusion of the parenchyma into the scrotal cavity.
- Echo structure — the parenchyma acquires heterogeneous echogenicity.
- Vascularity — using color Doppler flow mapping (CDUS), loss of blood supply to part or all of the testis is almost always detected.
To remember the pathways of lymphatic metastasis: lymph from the testes ascends to where they originated during embryogenesis—to the level of the renal hila. The left testis "favors" the left renal vein, and the right testis favors the aortocaval space.
Class and exam questions
Can color Doppler ultrasound accurately determine whether a tumor is malignant or benign?
No. Increased blood flow is common in tumors, but Doppler ultrasound does not reliably differentiate malignant lesions from benign ones. The presence of a solid intratesticular mass remains the primary criterion.
Is routine follow-up necessary for a patient with testicular microlithiasis?
There is no unified screening policy. Follow-up of isolated microlithiasis is not indicated. However, if additional risk factors are present (cryptorchidism, family history of cancer, atrophy), annual ultrasound is recommended up to age 55.
How to distinguish a multiloculated hydrocele from a hematoma?
The sonographic appearance of a septated hydrocele and an organizing traumatic hematoma can be practically identical. A properly taken medical history (history of recent trauma) plays a crucial role here.
What else to study on this topic
- Metastatic features: retroperitoneal anatomy and CT appearance of lymph nodes
- Specifics of MRI protocols (DWI, DCE) in complex scrotal masses
- Rhabdomyosarcoma and other extratesticular tumors in children
- Post-vasectomy changes: sperm granulomas and epididymal edema
- Nuclear medicine in urology: scintigraphy in splenogonadic fusion
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