Testicular Lymphoma
On this page
Direct answer
Primary testicular lymphoma is the commonest testicular tumour in men over 60, typically diffuse large B-cell lymphoma (DLBCL) presenting as a painless, rapidly enlarging testis that is easily mistaken for seminoma. It is the most aggressive lymphoma site in terms of relapse pattern, with a marked tendency to spread to the contralateral testis, the central nervous system, skin and Waldeyer's ring. Treatment combines orchidectomy (which provides full tissue for diagnosis), R-CHOP chemotherapy, intrathecal or systemic CNS prophylaxis, and consideration of contralateral testicular radiotherapy.
What you must remember
- Any testicular tumour in a man over 60 is lymphoma until proven otherwise; DLBCL is the dominant histology.
- Bilateral involvement is far commoner than with germ cell tumours — lymphoma eventually involves the contralateral testis in a substantial fraction of patients.
- CNS relapse (parenchymal brain and leptomeningeal) is a signature failure pattern, driving routine intrathecal prophylaxis.
- Ann Arbor staging with CT, PET and bone marrow assessment (plus CSF examination in many protocols) replaces the germ cell TNM approach.
- Spermatic cord invasion and epididymal involvement are frequent, and the mass is often disproportionately large and painless.
- In children, by contrast, lymphoma and leukaemia are the commonest secondary (metastatic) tumours of the testis — a classic distinction examiners test.
- Relapses tend to be late, beyond two years, which is unusual for other extranodal lymphomas.
How the diagnosis actually unfolds
A 68-year-old reports three months of painless left testicular enlargement; there is no fever or weight loss. Ultrasound shows a large, homogeneous, hypoechoic infiltrating mass replacing the testis, extending into the epididymis — a pattern that should raise lymphoma, since germ cell tumours are more often heterogeneous. The surgeons proceed with inguinal orchidectomy; frozen section may change the intraoperative plan, because lymphoma needs generous tissue for flow cytometry and immunohistochemistry (CD20 positivity confirms B-cell lineage), and a diagnosis of lymphoma makes extensive retroperitoneal dissection unnecessary.
Staging is then haematological: CT neck-chest-abdomen-pelvis, PET-CT where available, bone marrow biopsy, CSF analysis, LDH and beta-2 microglobulin. Markers AFP and beta-hCG are usually normal, which itself argues against germ cell tumour. Management is R-CHOP with CNS prophylaxis (intrathecal methotrexate and/or high-dose systemic methotrexate-containing regimens per protocol), and many centres add contralateral testicular radiotherapy (commonly in the order of 25-30 Gy) because the blood-testis barrier shelters the gonad from systemic chemotherapy. Outcomes are guarded, worse than stage-matched nodal DLBCL, and late relapses justify prolonged surveillance — a fact that distinguishes testicular lymphoma from most solid tumours in the exam hall.
Where students slip
The reflex answer "painless testicular swelling in an older man equals seminoma" is the trap; seminoma peaks at 35-45 years, and beyond 60 lymphoma overtakes it. The second slip is staging: ordering AFP, beta-hCG and abdominal CT for retroperitoneal nodes is germ cell logic; lymphoma demands Ann Arbor staging, PET and marrow. Third, candidates forget the two sanctuary sites — the brain and the contralateral testis — that explain the design of prophylaxis. Finally, in a child with a testicular mass and a known leukaemia or lymphoma, the lesion is likely a leukaemic infiltrate rather than a new primary; the viva answer is "treat the systemic disease, consider irradiation or chemotherapy infiltration, not orchidectomy first".
Frequently asked questions
What is the most common testicular tumour in a man over 60?
Primary testicular diffuse large B-cell lymphoma. Germ cell tumours dominate from adolescence to middle age, but lymphoma leads in the elderly.
Which histology characterises primary testicular lymphoma?
Diffuse large B-cell lymphoma in the great majority of cases, confirmed by CD20 positivity on immunohistochemistry, with flow cytometry on fresh tissue.
Why does testicular lymphoma need CNS prophylaxis?
Because the brain and leptomeninges are favoured relapse sites, with CNS recurrence reported in up to a fifth or more of historically untreated patients; intrathecal or systemic methotrexate-based prophylaxis reduces this.
Why is contralateral testicular radiotherapy considered?
The blood-testis barrier excludes systemic chemotherapy from the gonad, leaving the opposite testis at risk as a chemoresistant sanctuary site; radiotherapy of around 25-30 Gy is used to ablate it.
How does testicular lymphoma appear on ultrasound?
Typically as a large, homogeneous, hypoechoic mass infiltrating the testis, often with epididymal and spermatic cord extension, compared with the more heterogeneous appearance of germ cell tumours.