Testicular lymphoma is the most common testicular malignancy in men >50 years and constitutes 5% of all testicular tumors. The most common subtype is diffuse large B-cell lymphoma (DLBCL). Bilateral involvement is seen in 35% of cases — this feature is virtually pathognomonic for testicular lymphoma and distinguishes it from germ cell tumors. Ultrasound is the primary imaging modality; typical findings include homogeneous hypoechoic diffuse infiltration and marked hypervascularity. Testicular parenchymal architecture may be preserved or completely infiltrated. CNS involvement risk is high (10-15%) requiring prophylactic intrathecal chemotherapy. Prognosis in primary testicular lymphoma is relatively good with 5-year survival of 80-90%; however, late relapse risk exists.
Age Range
50-85
Peak Age
67
Gender
Male predominant
Prevalence
Uncommon
Primary testicular lymphoma is an extranodal lymphoma type developing from B-lymphocytes in the testis, which is an immune-privileged site. Since the blood-testis barrier protects lymphocytes from a selective immune environment, malignant lymphocytes can proliferate protected in this privileged setting. The most common subtype is DLBCL, creating diffuse infiltration in testicular interstitial tissue — showing a growth pattern that spreads between seminiferous tubules without disrupting normal parenchymal architecture (early stage) or completely replacing it (advanced stage). This infiltrative growth pattern manifests on US as diffuse hypoechoic appearance and preserved parenchymal linear pattern. Hypervascularity results from lymphoma cells secreting angiogenesis-stimulating cytokines (VEGF) and is visualized as markedly increased blood flow on Doppler. The frequency of bilateral involvement (35%) results from systemic lymphoma's testicular predilection and the blood-testis barrier providing protection for malignant cells on both sides. CNS involvement risk is high because CNS is also an immune-privileged site — therefore prophylactic intrathecal chemotherapy is added to standard treatment.
Homogeneous diffuse hypoechoic infiltration in both testes — bilateral testicular involvement in man >50 years is virtually pathognomonic for testicular lymphoma and differentiates from germ cell tumors.
Homogeneous diffuse hypoechoic infiltration is seen in the testis — reflecting widespread interstitial spread of lymphoma cells. In early stage, seminiferous tubule linear pattern may be preserved (striated pattern); in advanced stage, the testis becomes completely hypoechoic and enlarged. Echogenicity is markedly lower than normal testis. Focal mass formation may also be seen but diffuse infiltration is more typical. Similar findings should be searched in the contralateral testis (bilateral involvement 35%).
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Diffuse homogeneous hypoechoic infiltration is seen in the testis with preserved/disrupted normal parenchymal architecture; findings are consistent with testicular lymphoma.
Markedly increased vascularity is seen throughout the testis on color Doppler — linear vascular pattern is typical. The vascular pattern in lymphoma is generally more prominent and diffuse than in seminoma. Vascular structures course parallel to testicular parenchymal linear architecture (striated vascularity). Power Doppler better demonstrates hypervascularity.
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Diffuse marked hypervascularity with linear vascular pattern is seen in the testis on Doppler; finding is consistent with testicular lymphoma.
On MRI, lymphomatous infiltration shows markedly hypointense signal on T2-weighted images — opposite to normal testicular parenchyma (T2 hyperintense). Hypointensity reflects the high nuclear/cytoplasmic ratio and dense cellularity of lymphoma cells. Diffuse or focal involvement pattern may be seen. Bilateral involvement is well evaluated on T2.
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Diffuse hypointense signal is seen in the testis on T2-weighted images; finding is consistent with testicular lymphoma infiltration.
Marked diffusion restriction is seen in the lymphomatous testis on DWI — bright hyperintensity on high b-value images and markedly low signal on ADC maps. ADC values are typically <0.8 x 10-3 mm2/s, which may be even lower than seminoma (due to higher cellularity of lymphoma).
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Marked diffusion restriction is seen in the testis on DWI (ADC <0.8 x 10-3 mm2/s); finding is consistent with dense cellular infiltration suggesting lymphoma.
Bilateral testicular enlargement with homogeneous enhancement may be seen on CT. CT's main role is staging — evaluation of retroperitoneal, pelvic, and mediastinal lymphadenopathy, hepatosplenomegaly, and other extranodal involvement sites. Ann Arbor staging system is used. Testicular lymphoma typically presents as stage IE or IIE.
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Bilateral testicular enlargement is seen on CT with accompanying retroperitoneal lymphadenopathy; consistent with testicular lymphoma and PET-CT staging is recommended.
Intense FDG uptake is seen in the lymphomatous testis on PET-CT (SUVmax typically >10). Bilateral involvement, retroperitoneal LAP, and other extranodal site involvement are clearly evaluated on PET-CT. PET-CT plays a critical role in post-treatment response assessment (Deauville score) and residual/recurrent disease detection.
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Intense FDG uptake is seen in bilateral testes on PET-CT (SUVmax >10); accompanying retroperitoneal LAP and splenic involvement are present.
Criteria
Most common subtype (80-90%). >60 years peak. Testis as primary site. Stage IE (localized) or IIE (retroperitoneal LAP). R-CHOP + intrathecal prophylaxis + radiotherapy.
Distinct Features
Bilateral involvement 35%. CNS relapse risk 10-15% — prophylactic intrathecal MTX mandatory. Contralateral testis radiotherapy recommended. 5-year survival 80-90%.
Criteria
Spread of systemic lymphoma to the testis. Testicular involvement in the setting of known NHL or HL. More common in advanced-stage disease.
Distinct Features
Systemic disease findings (widespread LAP, splenomegaly, B symptoms) previously or simultaneously present. Testicular involvement usually bilateral. Treatment directed at systemic disease.
Criteria
Rare subtype. Seen in children and young adults (unlike DLBCL, not seen in elderly men). Very rapid growth — tumor doubling time 24-48 hours.
Distinct Features
Very high Ki-67 index (>99%). Very low ADC value on DWI (<0.5). High risk of tumor lysis syndrome. Intensive chemotherapy (R-hyper-CVAD or similar).
Distinguishing Feature
Seminoma: young male (20-40 years), FOCAL homogeneous hypoechoic mass, unilateral, AFP normal/hCG mildly elevated. Lymphoma: elderly male (>50), DIFFUSE infiltration, bilateral 35%, all markers normal.
Distinguishing Feature
Orchitis: diffuse heterogeneity + hypervascularity (similar to lymphoma!), but PAIN + FEVER + PYURIA accompany. Lymphoma: PAINLESS, no fever, markers normal. Chronic orchitis vs lymphoma differentiation may be difficult — biopsy needed.
Distinguishing Feature
Metastasis: in setting of known primary malignancy (prostate, lung, melanoma), usually focal mass(es), unilateral or bilateral. Lymphoma: primary testicular presentation, diffuse infiltration, >50 years.
Distinguishing Feature
Burned-out GCT: small hypoechoic scar/calcification + retroperitoneal mass, young male, AFP/hCG may be elevated. Lymphoma: enlarged hypoechoic testis, elderly male, AFP/hCG normal.
Urgency
urgentManagement
medicalBiopsy
NeededFollow-up
3-monthTesticular lymphoma diagnosis is confirmed by radical inguinal orchiectomy (biopsy + treatment). Treatment: R-CHOP chemotherapy + contralateral testis radiotherapy + prophylactic intrathecal MTX (CNS relapse risk 10-15%). 5-year survival in primary DLBCL is 80-90%. Late relapse risk exists (even after 5-10 years). Regular follow-up with PET-CT recommended (every 3-6 months first 2 years, then annually).
Testicular lymphoma is an aggressive malignancy but responds well to chemotherapy (R-CHOP). Orchiectomy is the first diagnostic and therapeutic step. Because testicular lymphoma crosses the blood-testis barrier, prophylactic contralateral testicular radiotherapy and intrathecal chemotherapy (CNS prophylaxis) are recommended. Prognosis is worse than germ cell tumors (5-year survival 50-60%). Relapse is frequently extranodal (CNS, contralateral testis, skin).