Testicular metastasis is a secondary tumor spread to the testis from another primary malignancy. It is rare (less than 1% of all testicular tumors) and usually part of advanced disseminated cancer. The most common primary sources are prostate carcinoma (35%), lung carcinoma (18%), melanoma (18%), renal cell carcinoma (9%), and gastrointestinal tumors. Spread routes: retrograde lymphatic (most common — prostate), hematogenous (melanoma, lung), direct invasion (prostate, bladder), and retrograde venous (renal). Bilateral involvement is seen in 15% of cases. On ultrasonography, it usually appears as focal hypoechoic mass(es) or rarely diffuse infiltration. Clinically, known malignancy history guides the diagnosis. Prognosis is generally poor — testicular metastasis reflects advanced disseminated disease and median survival is 12-24 months.
Age Range
50-80
Peak Age
65
Gender
Male predominant
Prevalence
Rare
Testicular metastasis develops through four main routes: (1) Retrograde lymphatic spread — most common in prostate carcinoma; tumor cells reach the testis via iliac and para-aortic lymph nodes retrogradely through spermatic cord lymphatics. (2) Hematogenous spread — common in melanoma and lung carcinoma; tumor emboli reach the testis via testicular arteries. (3) Direct invasion — direct extension of prostate or bladder carcinoma to the testis along the spermatic cord or vas deferens. (4) Retrograde venous spread — renal cell carcinoma spreading to the left testis via left renal vein → left spermatic vein. The hypoechoic appearance on US results from tumor cells replacing normal testicular architecture (seminiferous tubules) — irregular solid tumor tissue creates different acoustic impedance instead of homogeneous tubular structure. Diffuse infiltration pattern reflects widespread interstitial spread — tumor cells infiltrate between seminiferous tubules causing testicular enlargement and loss of homogeneity.
Newly developed intratesticular hypoechoic mass in a patient with known malignancy history + normal tumor markers (AFP, beta-hCG) + >50 years = consider metastasis. Bilateral involvement (15%) strengthens differentiation from primary GCT.
On B-mode ultrasonography, testicular metastasis usually appears as focal hypoechoic, well or poorly defined intratesticular mass. Single or multiple nodules may be seen. Size is usually 0.5-3 cm. Internal structure may be homogeneous or heterogeneous — may contain necrosis, hemorrhage, or cystic degeneration. In melanoma metastases, echogenic component may be seen due to high melanin content. Testicular size may be increased or normal. In diffuse infiltration pattern, the testis loses homogeneity and takes on hypoechoic-heterogeneous appearance.
Report Sentence
Focal hypoechoic mass(es) measuring (largest ___ mm) are seen in the right/left testicular parenchyma; metastasis is considered given the known ___ carcinoma history.
On color Doppler, vascularity of testicular metastasis varies by primary tumor. Melanoma metastases are hypervascular — showing prominent internal and peripheral vascularity. Prostate metastases show low-to-moderate vascularity. Lung carcinoma metastases show variable vascularity. Presence of hypervascularity supports malignancy but absence does not exclude it. Peripheral 'rim' vascularity may be seen in some metastases.
Report Sentence
On color Doppler, the intratesticular mass(es) show ___ vascularity; vascular pattern consistent with malignancy.
On T2-weighted MR images, testicular metastasis appears as a hypointense mass replacing normal testicular high signal. Normal testicular parenchyma is markedly hyperintense on T2; metastatic tissue shortens T2 due to cellularity and shows low signal. Shows heterogeneous enhancement on contrast-enhanced series. Restricted diffusion on DWI reflects high cellularity. MRI is complementary to US in equivocal cases and testicular tumor characterization.
Report Sentence
On MRI, a T2 hypointense mass with heterogeneous enhancement on contrast-enhanced series is seen in the right/left testicular parenchyma; restricted diffusion is present — consistent with metastatic involvement.
On CT, testicular metastasis may present with testicular mass along with retroperitoneal lymphadenopathy and metastatic findings in other organs. Testicular mass may be incidentally detected on staging CT of the primary tumor. Retroperitoneal, pelvic, and inguinal lymphadenopathy should be evaluated. Spermatic cord involvement and perivascular spread may be detected on CT.
Report Sentence
Mass in the right/left testis is seen along with retroperitoneal lymphadenopathy and metastatic lesions in ___ organ(s); disseminated metastatic disease consistent with known ___ carcinoma.
Melanoma metastases may show high signal on T1-weighted images — this results from the paramagnetic effect of melanin pigment. Melanin shortens T1 relaxation and produces bright signal. This finding is highly specific for melanoma metastasis — other testicular metastases are isointense or mildly hypointense on T1. This finding is not seen in amelanotic melanoma metastases. On T2, melanotic metastases may be hypointense (T2-shortening effect of melanin).
Report Sentence
On MRI, a T1 hyperintense mass is seen in the testicular parenchyma, consistent with melanin content; melanoma metastasis is considered given the known melanoma history.
Criteria
Most common primary (35%). Retrograde lymphatic or direct invasion. Usually advanced prostate cancer.
Distinct Features
Hypoechoic nodule(s) on US, low-moderate vascularity. Elevated PSA. May be under hormonal therapy.
Criteria
Hematogenous spread. Hypervascular. High signal on T1 MRI (melanin).
Distinct Features
Prominent hypervascularity on Doppler. T1 hyperintensity on MRI pathognomonic. Bull's-eye pattern may also be seen.
Criteria
Hematogenous spread. Small cell and non-small cell types. Variable vascularity.
Distinct Features
Single or multiple hypoechoic nodules on US. Usually part of advanced disease. Mediastinal/hilar LAP and primary lung lesion on CT.
Distinguishing Feature
Seminoma usually in young men (20-40), single homogeneous hypoechoic mass, beta-hCG may be mildly elevated; metastasis >50 years, known malignancy, AFP/beta-hCG normal.
Distinguishing Feature
Lymphoma >60 years, may be bilateral (35%), diffuse infiltration common, hypervascular; metastasis also >50 years and may be bilateral — differentiation by clinical + biopsy.
Distinguishing Feature
Orchitis diffuse testicular enlargement, pain, fever, epididymitis accompanies, hypervascular; metastasis usually painless, focal mass, no fever.
Distinguishing Feature
Burned-out GCT small, calcified scar; metastasis non-calcified solid mass. Burned-out GCT retroperitoneal mass + regressed primary.
Urgency
urgentManagement
medicalBiopsy
NeededFollow-up
specialist-referralTesticular metastasis reflects advanced disseminated disease and treatment is directed at the primary tumor. Diagnosis is typically confirmed by radical inguinal orchiectomy or US-guided biopsy. Systemic chemotherapy/immunotherapy/hormone therapy directed at the primary tumor is administered. Prognosis is generally poor (median survival 12-24 months). Testosterone replacement therapy should be planned in bilateral involvement.
Testicular metastasis is generally a finding of advanced-stage disease and carries a poor prognosis. Treatment is directed at systemic therapy of the primary tumor. Orchiectomy may be performed for diagnostic and palliative purposes. Prostate cancer metastasis may respond to hormonal therapy. In all older men with painless testicular mass, known malignancy history should be queried and tumor markers evaluated.