Interventional Radiology Imaging

What Imaging Is Best for Initial Staging of ALL in an Asymptomatic Boy?

·
What Imaging Is Best for Initial Staging of ALL in an Asymptomatic Boy?

A pediatric oncologist has just delivered the diagnosis of acute lymphoblastic leukemia (ALL) to the parents of a young boy. The diagnosis, confirmed by bone marrow biopsy, is a life-altering event, but the child himself feels well and has no specific complaints. Now, the clinical team faces the critical task of initial staging. Beyond the marrow and cerebrospinal fluid analysis, a key question arises: is there occult disease elsewhere? Specifically, does this asymptomatic child require imaging to complete his staging workup? This article provides a detailed workflow for this precise scenario, explaining why the American College of Radiology (ACR) Appropriateness Criteria rates US scrotum as ‘May be appropriate (Disagreement)’ for the initial staging of an asymptomatic male child with ALL.

## Who Fits This Clinical Scenario for Leukemia Staging?
This guidance applies to a very specific patient population: a male child newly diagnosed with acute lymphoblastic leukemia who is, at the time of diagnosis, asymptomatic. This means the patient has no focal neurologic symptoms, no localized bone pain, no palpable masses, and no signs or symptoms of respiratory distress.

This workflow is intended for initial staging only, prior to the initiation of systemic therapy.

It is crucial to distinguish this presentation from similar but distinct clinical situations that require a different imaging approach. This guidance does not apply to:

  • Symptomatic Children: A child with ALL presenting with headaches, seizures, cranial nerve palsies, or focal bone pain requires a different workup, often involving MRI of the brain and spine or targeted imaging of the painful area.
  • Female Children: The testes are a unique sanctuary site for leukemia. The imaging workup for an asymptomatic female child with ALL is different, as routine screening for ovarian involvement is not standard practice.
  • Adults with ALL: Staging and surveillance protocols for adults differ from pediatric guidelines and represent a separate clinical scenario.
  • Other Leukemia Subtypes: This guidance is specific to ALL. The staging for acute myeloid leukemia (AML), chronic myeloid leukemia (CML), or chronic lymphocytic leukemia (CLL) follows different pathways.

## What Diagnoses Are You Working Up in This Scenario?
While the primary diagnosis of ALL is already established, staging imaging aims to identify or rule out extramedullary disease—the spread of leukemia beyond the bone marrow. In an asymptomatic male child, the primary concern is occult involvement of sanctuary sites, which can influence risk stratification and treatment intensity.

Testicular Leukemia: The most significant consideration in this scenario is leukemic infiltration of the testes. The testes are a known sanctuary site, meaning systemic chemotherapy may not penetrate the blood-testis barrier as effectively. Undetected testicular disease at diagnosis can be a source of later relapse. While clinical testicular involvement (a palpable, firm, painless mass) is found in a minority of boys at diagnosis, subclinical or occult disease can be present without any physical findings. Imaging serves as a screening tool to detect this occult involvement.

Mediastinal Involvement: Less commonly, particularly in patients with T-cell ALL, a mediastinal mass (representing thymic or lymph node infiltration) can be present. While large masses often cause symptoms like cough or shortness of breath, smaller ones may be clinically silent. This is a secondary consideration in the imaging workup of an asymptomatic patient.

Absence of Widespread Disease: The “asymptomatic” nature of the patient makes widespread osseous or central nervous system (CNS) disease unlikely. Therefore, the goal of imaging is not a broad search for disease but a targeted evaluation of high-risk sites.

## Why Is Scrotal Ultrasound Considered for Staging Asymptomatic ALL in Boys?
For the initial staging of an asymptomatic male child with ALL, the ACR panel rates US scrotum as ‘May be appropriate (Disagreement)’. This nuanced rating reflects its value as a targeted, safe screening tool, while also acknowledging that its routine use varies by institutional protocol.

The primary rationale for considering scrotal ultrasound is its ability to detect occult testicular infiltration. Ultrasound is highly effective at evaluating testicular parenchyma for abnormalities such as diffuse enlargement, heterogeneity, or focal hypoechoic masses that suggest leukemic involvement. The key advantages of ultrasound in this pediatric setting are:

  • No Ionizing Radiation: US scrotum has a pediatric relative radiation level of 0 mSv, a critical consideration in children who will undergo numerous future medical procedures.
  • High Resolution: Modern ultrasound provides excellent spatial resolution of the testicular architecture, superior to that of CT or MRI for this specific application.
  • Accessibility and Low Cost: It is a widely available, non-invasive, and relatively inexpensive examination.

The “Disagreement” in the ACR rating stems from the low prevalence of occult testicular disease in truly asymptomatic boys with a normal physical exam. Some cooperative group protocols and institutional guidelines do not mandate screening ultrasound for all boys, relying instead on a meticulous physical examination. However, other institutions advocate for baseline ultrasound in all male patients, arguing that it can identify a small but important subset of patients who require more intensive therapy (like testicular radiation) to prevent relapse.

### Why Other Studies Are Not Recommended

In contrast, more extensive imaging modalities are rated ‘Usually not appropriate’ for this specific scenario due to the unfavorable risk-benefit balance.

  • CT abdomen and pelvis with IV contrast: This study delivers a significant radiation dose (pediatric RRL ☢☢☢☢ 3-10 mSv) with very low yield for finding unexpected, clinically significant disease in an asymptomatic child. It also provides poor detail of the testicular parenchyma compared to ultrasound.
  • FDG-PET/CT whole body: While useful in other cancers like lymphoma, PET/CT is ‘Usually not appropriate’ for routine ALL staging. It involves a high radiation dose (pediatric RRL ☢☢☢☢ 3-10 mSv) and its role in detecting occult testicular disease or altering initial therapy in this context is not established. Diffuse bone marrow involvement can also make interpretation challenging.

A Radiography chest is also rated ‘May be appropriate (Disagreement)’. It is considered for a different reason: to evaluate for a mediastinal mass. This is often performed as a baseline study, especially if the ALL subtype is T-cell or if the white blood cell count is very high. It uses a very low dose of radiation (pediatric RRL ☢ <0.03 mSv). Once you've decided on US scrotum, our protocol guide covers the technique, contrast, and reading principles: US Scrotum.

## What’s Next After Scrotal Ultrasound? Downstream Workflow
The results of the scrotal ultrasound directly influence the patient’s risk stratification and subsequent treatment plan. The downstream pathway diverges based on the findings.

  • If the study is positive: Findings consistent with leukemic infiltration (e.g., testicular enlargement, focal hypoechoic lesions) confirm overt extramedullary disease. This finding upstages the patient to a higher risk category. The treatment plan will be intensified, most commonly by adding radiation therapy directed at the testes to the systemic chemotherapy regimen. This is critical for eradicating the sanctuary site disease and preventing relapse.
  • If the study is negative: A normal scrotal ultrasound is reassuring. It suggests the absence of overt testicular disease. The patient’s risk stratification and treatment will proceed based on other established factors, such as age, initial white blood cell count, cytogenetics, and response to induction therapy (minimal residual disease). No further testicular-specific therapy is indicated at this time.
  • If the study is indeterminate: Occasionally, ultrasound may reveal non-specific findings, such as a small hydrocele, epididymal cyst, or subtle heterogeneity. In these cases, close collaboration between the oncologist and a pediatric radiologist is essential. Often, these findings are benign and incidental. A short-term follow-up ultrasound may be recommended to ensure stability, but these findings typically do not alter the initial treatment plan unless they are highly suspicious.

## Pitfalls to Avoid (and When to Get Help)
Navigating the initial staging of pediatric ALL requires a focused approach. Avoiding common pitfalls can prevent unnecessary radiation exposure and ensure accurate risk assessment.

1. The “Shotgun” Imaging Approach: The most significant pitfall is ordering extensive imaging like whole-body CT or PET/CT for an asymptomatic child. This is contrary to evidence-based guidelines and exposes the child to substantial, unnecessary radiation for a very low diagnostic yield.
2. Substituting Imaging for Physical Exam: Ultrasound is a supplement to, not a replacement for, a careful, thorough physical examination of the testes. An abnormal exam finding mandates an ultrasound, regardless of institutional screening protocols.
3. Misinterpreting Incidental Findings: Benign findings like small cysts or hydroceles are common in children. It’s crucial to avoid over-calling these as leukemic infiltration, which could lead to inappropriate and toxic therapies like radiation.
4. Applying this Protocol to Symptomatic Patients: If a child develops focal symptoms at any point (e.g., headache, severe localized bone pain, respiratory distress), this asymptomatic workflow is no longer valid. Escalate immediately to the appropriate targeted imaging (e.g., brain MRI, spine MRI, or radiographs of the painful area) and consult with the pediatric oncology team.

## Related ACR Topics and Tools
This article focuses on one specific clinical variant. For a comprehensive overview of imaging across all common leukemia-related scenarios, please consult our parent guide.

For additional decision support and technical guidance, the following GigHz resources are available:

Frequently Asked Questions

Why is scrotal ultrasound rated ‘May be appropriate (Disagreement)’ and not ‘Usually appropriate’?

The ‘Disagreement’ reflects a lack of universal consensus. Because occult testicular leukemia is rare in asymptomatic boys with a normal physical exam, some major pediatric oncology cooperative groups and institutions do not mandate screening ultrasound for every patient. They rely on the physical exam alone. Others prefer a baseline ultrasound for all boys. The ACR rating acknowledges this valid difference in practice patterns.

Should I also order a chest X-ray for this patient?

A chest X-ray is also rated ‘May be appropriate (Disagreement)’. It serves a different purpose: to screen for a mediastinal mass, which is more common in T-cell ALL. Many institutions perform a baseline two-view chest radiograph as part of the initial workup, as it is a low-dose study that can provide important information about potential airway compression before sedation or anesthesia.

If this patient were a girl, what imaging would be needed for staging?

For an asymptomatic girl with newly diagnosed ALL, routine screening imaging for extramedullary disease (such as a pelvic ultrasound to look for ovarian involvement) is not standard practice. Ovarian involvement is much rarer than testicular involvement and is not considered a common sanctuary site in the same way. Therefore, no imaging is typically recommended for this specific purpose in an asymptomatic female child.

Does a normal scrotal ultrasound definitively rule out testicular leukemia?

A normal ultrasound is highly reassuring and effectively rules out overt or clinically significant testicular involvement. However, it cannot detect microscopic disease. The management of microscopic residual disease is addressed by systemic chemotherapy and monitoring for minimal residual disease (MRD) in the bone marrow, not by screening imaging.

If the ultrasound is positive, is a biopsy of the testicle needed for confirmation?

No, a testicular biopsy is generally not performed in this setting. The combination of a known ALL diagnosis and characteristic findings on ultrasound (e.g., diffuse enlargement and infiltration) is considered sufficient to diagnose testicular leukemia. A biopsy carries risks of bleeding, infection, and potential tumor seeding, and is avoided.

Reviewed by Pouyan Golshani, MD, Interventional Radiologist — May 30, 2026