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A 7-year-old boy completed chemotherapy for precursor B-cell acute lymphoblastic leukemia 2 years ago and has remained in complete remission. He is brought to the clinic because of gradually progressive, painless enlargement of the left testis for 4 weeks. There is no history of fever, trauma, dysuria, or scrotal pain. Examination reveals a firm, non-tender enlarged left testis with no overlying erythema. There is no hepatosplenomegaly or lymphadenopathy. Complete blood count is within normal limits.
What is the most likely diagnosis?
A. Epididymo-orchitis
B. Hydrocele
C. Isolated testicular relapse of ALL
D. Testicular torsion
E. Varicocele
Correct answer & Explanation:
Correct Answer: C. Isolated testicular relapse of ALL
Explanation
The testes are a recognized sanctuary site for leukemic cells because of limited penetration of some chemotherapeutic agents through the blood-testis barrier. A child previously treated for ALL who develops a gradually progressive, painless, firm unilateral testicular enlargement should be presumed to have testicular relapse until proven otherwise, even if the peripheral blood counts are normal.
Following suspicion of testicular relapse, staging should include bone marrow examination and cerebrospinal fluid analysis to determine whether the relapse is isolated or combined, as this influences prognosis and treatment.
Why the other options are incorrect
A. Epididymo-orchitis
Usually presents with acute pain, tenderness, fever, and scrotal erythema rather than a painless, firm testicular swelling.
B. Hydrocele
Produces a fluctuant, transilluminant scrotal swelling rather than a firm intratesticular mass.
C. Isolated testicular relapse of ALL
Correct. A painless, firm unilateral testicular enlargement in a child with previous ALL is highly suggestive of testicular relapse.
D. Testicular torsion
Typically presents with sudden, severe scrotal pain, swelling, and an absent cremasteric reflex.
E. Varicocele
Usually occurs in adolescents, is more common on the left side, and feels like a “bag of worms” rather than a firm enlarged testis.
Learning Point
Testicular relapse is an important extramedullary relapse of childhood ALL. Key clinical features include:
- Painless unilateral or bilateral testicular enlargement
- Firm, non-tender testis
- Normal peripheral blood counts may be present
- Bone marrow and CNS evaluation are essential to determine whether relapse is isolated or combined.
