Interventional Radiology Imaging

What Imaging Is Best for Suspected Richter Syndrome in Chronic Lymphocytic Leukemia?

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What Imaging Is Best for Suspected Richter Syndrome in Chronic Lymphocytic Leukemia?

It’s late in the afternoon clinic, and you’re seeing a 68-year-old patient with a long-standing diagnosis of chronic lymphocytic leukemia (CLL), who has been on watch-and-wait for years. Today, he reports two months of drenching night sweats, unintentional weight loss, and profound fatigue. On exam, you palpate a new, firm, rapidly enlarging supraclavicular lymph node. Your primary concern is histologic transformation into an aggressive lymphoma—Richter syndrome. The immediate clinical question is how to best evaluate the extent of disease to guide the essential next step: biopsy. According to the American College of Radiology (ACR) Appropriateness Criteria, for an adult undergoing surveillance of CLL with suspected histologic transformation, a CT chest abdomen pelvis with IV contrast is a Usually Appropriate initial imaging study.

Who Fits This Clinical Scenario?

This imaging workflow is specifically for an adult patient with a known, established diagnosis of chronic lymphocytic leukemia who now presents with new, concerning clinical or laboratory signs suggesting histologic transformation. These signs often include:

  • Rapidly progressive or bulky lymphadenopathy
  • Development of B symptoms (unexplained fever, drenching night sweats, >10% weight loss)
  • Significant and progressive splenomegaly
  • A sudden, sharp rise in lactate dehydrogenase (LDH) levels
  • New extranodal disease

This guidance is distinct from other leukemia-related scenarios. This workflow does not apply to:

  • Initial staging of any leukemia: Patients newly diagnosed with acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), or chronic myeloid leukemia (CML) follow different imaging pathways. This scenario is for surveillance of known CLL.
  • Asymptomatic CLL surveillance: Routine imaging is not indicated for stable, asymptomatic CLL patients. This workflow is triggered by a specific clinical suspicion of transformation.
  • Post-therapy evaluation: Imaging to assess treatment response for a known lymphoma or other malignancy involves different criteria and timing.

The key differentiator is the combination of a baseline CLL diagnosis and a new, acute clinical change that raises suspicion for a high-grade transformation event.

What Diagnoses Are You Working Up in This Scenario?

When ordering imaging for suspected Richter syndrome, you are evaluating a differential that hinges on distinguishing aggressive transformation from other causes of clinical decline. The imaging findings will help prioritize the next steps, most critically, identifying an optimal biopsy target.

Richter Syndrome (Richter Transformation)
This is the primary diagnosis of concern and the reason for the urgent workup. Richter syndrome is the transformation of CLL into a high-grade, aggressive lymphoma, most commonly diffuse large B-cell lymphoma (DLBCL). It is a clinically significant event associated with a poor prognosis and requires immediate, aggressive therapy. Imaging is crucial to identify the extent of disease, including bulky nodal masses, extranodal sites, and organomegaly, and to select the most accessible and representative site for biopsy.

Progressive Chronic Lymphocytic Leukemia
The patient’s symptoms could represent an acceleration of their underlying CLL without histologic transformation. In this case, imaging might show a generalized, but less dramatic, increase in the size of lymph nodes and the spleen compared to prior studies. While still clinically important, this finding points toward a change in CLL management rather than the distinct, aggressive lymphoma therapy required for Richter syndrome.

Infection
Patients with CLL are immunocompromised and susceptible to a wide range of infections. B symptoms like fever and night sweats can be classic signs of an infectious process. Imaging can help identify potential sources, such as pulmonary consolidation, intra-abdominal abscesses, or disseminated fungal disease, which can mimic malignant progression.

Second Primary Malignancy
Having CLL increases the risk of developing other cancers. The constitutional symptoms and new adenopathy could be the first sign of a new, unrelated solid tumor or another hematologic malignancy. A comprehensive torso CT provides a thorough survey for an unexpected primary cancer in the lungs, liver, kidneys, or other organs.

Why Is CT Chest, Abdomen, and Pelvis with IV Contrast a Recommended Study?

The ACR rates CT chest abdomen pelvis with IV contrast as Usually Appropriate for this scenario because it provides a rapid, comprehensive, and widely available assessment of the key anatomical areas affected by lymphoproliferative disorders. Its utility is rooted in its ability to accurately characterize the extent of disease, which is critical for both diagnosis and subsequent management.

The primary role of the CT is to map out the burden of disease. It excels at identifying and measuring lymphadenopathy in the mediastinum, retroperitoneum, and pelvis. It also clearly delineates hepatosplenomegaly and can detect extranodal involvement in organs like the liver, spleen, kidneys, and bowel wall. The use of intravenous contrast is essential to differentiate lymph nodes from blood vessels and to evaluate for organ infiltration and other potential pathologies, including infection or a second primary tumor.

It is important to note that FDG-PET/CT is also rated Usually Appropriate and is an excellent alternative, or in some centers, the preferred initial study. Its advantage is the addition of functional information; the avidity of 18F-fluorodeoxyglucose (FDG) uptake, quantified by the maximum standardized uptake value (SUVmax), can help differentiate high-grade transformation (typically highly FDG-avid) from low-grade CLL (less avid). This makes PET/CT exceptionally valuable for guiding biopsy to the most metabolically active, and therefore most diagnostically useful, site.

In contrast, other modalities are rated lower for this initial systemic survey:

  • MRI abdomen and pelvis is rated Usually Not Appropriate. While excellent for problem-solving specific organ-based questions, it is less efficient than CT for a comprehensive survey of nodal disease throughout the chest, abdomen, and pelvis. It is slower, more susceptible to motion artifact, and offers no clear diagnostic advantage in this specific context.
  • Radiography (chest or abdomen) is also Usually Not Appropriate. It lacks the cross-sectional detail needed to evaluate the retroperitoneum, measure nodal burden accurately, or assess for organ infiltration. Its sensitivity for the key findings in this workup is unacceptably low.

The recommended CT study carries a radiation dose of ☢☢☢☢ (10-30 mSv). This is a moderate to high dose, but it is justified by the high clinical stakes of missing a diagnosis of Richter syndrome. Once you’ve decided on this study, our protocol guide covers the technique, contrast, and reading principles: CT Chest/Abdomen/Pelvis with IV Contrast.

What’s Next After CT? Downstream Workflow

The results of the CT scan directly inform the subsequent clinical pathway. The goal of imaging is not to make a definitive diagnosis but to guide the next, most critical action: obtaining tissue for histologic confirmation.

  • If the study is positive for aggressive features: Findings such as a dominant, bulky nodal mass (e.g., >5 cm), rapidly enlarging nodes compared to prior imaging, or evidence of extranodal disease strongly support the suspicion of Richter syndrome. The next step is an excisional biopsy of the most accessible and representative lymph node identified on the scan. If a PET/CT was performed, the target should be the most FDG-avid lesion. Fine-needle aspiration is often insufficient; an excisional biopsy is required to provide enough tissue for the architectural and immunophenotypic analysis needed to confirm transformation.
  • If the study is negative or shows only indolent progression: If the CT shows no new bulky disease and only mild, diffuse progression of previously known adenopathy, Richter syndrome is less likely. The clinical picture may be more consistent with progressive CLL or an alternative diagnosis like infection. The next steps might include laboratory workup for infection, observation, or consideration of a lymph node biopsy to rule out transformation if clinical suspicion remains high despite imaging findings.
  • If the findings are indeterminate: In cases where CT findings are ambiguous, an FDG-PET/CT can be a powerful next step to assess the metabolic activity of the disease. High FDG avidity would increase suspicion for Richter’s and provide a clear biopsy target, while low avidity would argue against it.

Pitfalls to Avoid (and When to Get Help)

In the workup for suspected Richter syndrome, several common pitfalls can delay diagnosis or lead to misinterpretation. Be mindful of the following:

  • Accepting an inadequate biopsy: Do not rely on a fine-needle aspiration (FNA) or core needle biopsy if Richter syndrome is suspected. These methods often fail to provide sufficient tissue to assess lymph node architecture, which is critical for diagnosis. Advocate for an excisional biopsy.
  • Omitting IV contrast: Ordering a non-contrast CT significantly degrades its diagnostic utility. Contrast is essential for delineating vascular structures, assessing organ enhancement, and identifying necrotic areas within lymph nodes. Ensure the patient’s renal function is adequate for contrast administration.
  • Misattributing B symptoms: While B symptoms are a hallmark of transformation, always maintain a broad differential, especially for infection. A negative imaging scan for bulky disease should prompt a vigorous search for an infectious etiology.

If the clinical picture and imaging findings are discordant, or if a safe biopsy target cannot be identified, consultation with an interventional radiologist or surgeon is the appropriate escalation to plan the best approach for obtaining a tissue diagnosis.

Related ACR Topics and Tools

This article covers a single, specific clinical scenario. For a broader view of imaging across all common presentations of leukemia, or to explore the technical details of the recommended studies, the following resources are available.

Frequently Asked Questions

Is FDG-PET/CT better than a standard contrast-enhanced CT for suspected Richter syndrome?

Both CT with contrast and FDG-PET/CT are rated ‘Usually Appropriate’ by the ACR. FDG-PET/CT offers the advantage of functional information, identifying metabolically active sites that are more likely to represent high-grade transformation. This makes it superior for guiding a biopsy to the highest-yield location. However, a contrast-enhanced CT is often more readily available, faster, and provides excellent anatomic detail. The choice may depend on institutional preference, availability, and the specific clinical question.

If my patient has renal insufficiency, can I order a non-contrast CT?

A non-contrast CT is significantly less informative and is rated ‘Usually Not Appropriate’ for this indication. It makes distinguishing lymph nodes from blood vessels difficult and poorly assesses organ involvement. If there is a contraindication to iodinated contrast, alternative strategies should be considered, such as pre-medication, hydration, or using a different modality like FDG-PET/CT (where the CT portion can be performed without contrast for attenuation correction and localization) or, in select cases, MRI after consultation with a radiologist.

What specific CT finding is most suggestive of Richter transformation?

While no single finding is pathognomonic, the most suggestive feature is the presence of a dominant, rapidly growing, bulky lymph node or nodal mass (often defined as greater than 5 cm) in the setting of more generalized, smaller-volume adenopathy. High FDG avidity (e.g., SUVmax > 5) on a PET/CT is also highly suspicious. However, the definitive diagnosis always requires histologic confirmation from a biopsy.

Does a negative CT or PET/CT scan rule out Richter syndrome?

A negative scan makes Richter syndrome much less likely, but it cannot completely rule it out, especially in early or focal transformation. If strong clinical signs persist despite negative imaging (e.g., a single, rapidly growing palpable node, or dramatically rising LDH), a biopsy of the most clinically suspicious site is still warranted. Imaging is a guide, but clinical judgment and histologic proof are paramount.

How often should I perform surveillance imaging on a stable CLL patient to screen for Richter syndrome?

Routine surveillance imaging is not recommended for asymptomatic or stable CLL patients. Imaging should only be performed when there is a specific clinical change—such as the development of B symptoms, rapidly enlarging lymph nodes, or unexplained cytopenias—that raises suspicion for disease progression or transformation.

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