What does a 9 mm lucent/lytic lesion in the left C6 articular process of a 75‑year‑old man represent and how should it be managed, including the role of a nuclear‑medicine bone scan?

Management of a 9mm Lucent/Lytic Lesion in the C6 Articular Process

What This Finding Means

A 9mm lucent/lytic lesion in the left C6 articular process of a 75-year-old man is most likely a benign entity (bone island, degenerative cyst, or healing bone), but requires systematic evaluation to exclude metastatic disease, multiple myeloma, or primary bone tumor. 1

Key Diagnostic Considerations

• Size matters: Lesions <5mm generally require no further workup and typically represent benign bone islands or healing bone, but at 9mm this lesion crosses the threshold requiring evaluation 2
• Location in the articular process: This anatomically complex site makes CT the preferred initial advanced imaging modality over plain radiographs alone 1
• Age-related context: In a 75-year-old, the differential includes degenerative cysts (common), metastatic disease (if cancer history exists), multiple myeloma, or benign bone lesions 1

Critical Point About Malignancy Risk

In patients without known malignancy, a solitary lytic lesion near bone—even if appearing aggressive—statistically represents new metastatic disease or myeloma in essentially 0% of cases. 3 However, this statistical reassurance does NOT eliminate the need for proper workup, as the consequences of missing malignancy are severe 1.

Recommended Diagnostic Algorithm

Step 1: Obtain Nuclear Medicine Bone Scan (As Already Suggested)

The bone scan recommendation in your report is appropriate and should be pursued on a non-emergent basis. 1

• Purpose: Bone scintigraphy using 99mTc-labeled bisphosphonate detects focal increases in tracer uptake at sites of active bone formation, often before bone destruction is visible on radiographs 1
• Sensitivity: More sensitive than plain radiographs for detecting skeletal pathology (except in multiple myeloma where it may be falsely negative) 1
• What it tells you: A "hot spot" suggests metabolically active disease (infection, tumor, healing fracture); a "cold" or normal scan makes aggressive pathology less likely 1

Step 2: Obtain CT of the Cervical Spine with Bone Windows

CT should be performed concurrently with the bone scan to evaluate cortical bone detail in this anatomically complex region. 1

• Why CT is essential here: The articular process has complex anatomy where plain radiographs are inadequate; CT provides excellent visualization of bony destruction, sclerosis, and cortical integrity 1
• What to look for: Cortical destruction, soft tissue extension, periosteal reaction, and matrix mineralization patterns that indicate biological activity 1

Step 3: Consider MRI with Gadolinium if Findings Are Concerning

MRI is the gold standard for characterizing bone lesions and should be obtained if the bone scan is positive or CT shows aggressive features. 1, 4, 5

• Superior sensitivity: MRI directly visualizes tumor tissue based on signal intensity differences from bone marrow, unlike indirect changes on X-ray or bone scan 1
• Critical for spine: Essential for detecting spinal cord compression or soft tissue extension that could require urgent intervention 1
• Timing: Can be deferred if bone scan and CT are reassuring, but mandatory if either suggests active pathology 4, 5

Step 4: Laboratory Workup (If Imaging Suggests Active Disease)

If bone scan shows uptake or CT demonstrates aggressive features, immediately order the following labs to exclude multiple myeloma: 1, 4, 5

• Serum protein electrophoresis (SPEP) with immunofixation 1, 4, 5
• Serum free light chain assay (kappa/lambda ratio) 1, 4, 5
• Complete blood count 1, 4, 5
• Serum calcium, creatinine, and albumin (CRAB criteria) 4, 5
• Quantitative immunoglobulins (IgG, IgA, IgM) 5

Rationale: Multiple myeloma can present as solitary bone lesions and is often missed on bone scans; laboratory screening is essential 1

Step 5: Whole-Body Imaging if Malignancy Is Suspected

Whole-body low-dose CT or bone scan is mandatory to determine if the lesion is solitary or part of systemic disease. 4, 5, 2

• Why this matters: Solitary lesions have vastly different management than multiple lesions (e.g., solitary plasmacytoma vs. multiple myeloma) 1, 4
• Detection advantage: Whole-body CT detects 60% more relevant findings than conventional X-rays 5

Step 6: Biopsy Decision-Making

Biopsy is strongly recommended if imaging is equivocal or suggests malignancy, especially in bone-only disease with few lesions. 1

• When biopsy is mandatory: Equivocal imaging, no known primary malignancy, or when diagnosis would change management 1
• Technique: CT-guided biopsy is preferred for precise localization in the cervical spine 1
• Pathology requirements: Tissue must be assessed by a specialist familiar with bone pathology; include flow cytometry if plasma cell dyscrasia is suspected 1, 4, 5

Common Pitfalls to Avoid

Do Not Rely Solely on Plain Radiographs

• Plain films miss lesions until >50% of bone mineral content is lost 1, 2
• CT is essential in the cervical spine due to complex anatomy 1

Do Not Skip the Bone Scan

• The bone scan was appropriately recommended and should not be dismissed as unnecessary 1
• Exception: If you proceed directly to MRI with gadolinium and whole-body imaging, the bone scan may be redundant 1, 4

Do Not Assume Benignity Without Workup

• Even if statistically likely benign, the consequences of missing malignancy are severe (spinal cord compression, pathologic fracture) 1
• A negative bone scan has high negative predictive value and can provide reassurance 1

Do Not Miss Multiple Myeloma

• Myeloma bone disease is often missed on bone scans because it lacks the osteoblastic reaction that causes tracer uptake 1
• If myeloma is suspected, proceed directly to MRI and laboratory workup rather than relying on bone scan 1

Do Not Forget Infection

• Osteomyelitis can present as a lytic lesion and should be considered if there are risk factors (recent surgery, immunosuppression, trauma) 1
• MRI is superior to CT for detecting infection and associated soft tissue involvement 1

Practical Management Summary

For this 75-year-old patient with a 9mm lytic lesion in C6:

1. Proceed with the bone scan as recommended (non-emergent) 1
2. Add CT cervical spine with bone windows to evaluate cortical detail 1
3. If bone scan is "hot" or CT shows aggressive features: Order MRI with gadolinium + myeloma labs + whole-body imaging 1, 4, 5
4. If bone scan is negative and CT shows benign features: Consider short-interval follow-up imaging (3-6 months) to document stability 1, 6
5. If any uncertainty remains after imaging: Pursue CT-guided biopsy for definitive diagnosis 1

The goal is to confidently exclude malignancy while avoiding unnecessary invasive procedures for benign lesions. 1, 6