What are punch‑out lesions on radiographs (X‑ray)?

What Are Punch-Out Lesions on X-Ray?

Punch-out lesions are sharply demarcated, round or oval lytic (bone-destroying) defects visible on radiographs that appear as if a hole has been "punched" through the bone, most characteristically seen in multiple myeloma affecting the skull (creating the pathognomonic "raindrop skull" appearance) and other plasma cell dyscrasias.

Radiographic Characteristics

Punch-out lesions have several distinctive features on plain radiography:

• Sharply defined borders with smooth, round margins
• Central end-plate lysis in vertebral involvement
• No surrounding sclerotic rim (unlike many benign lesions)
• Multiple scattered distribution creating a "raindrop" pattern when numerous 1

The term specifically describes the appearance of discrete, well-circumscribed osteolytic areas that look as though a circular punch tool has removed bone tissue.

Primary Clinical Context: Multiple Myeloma

Punch-out lesions are pathognomonic for calvarial multiple myeloma when they create the "raindrop skull" appearance 1. In myeloma:

• Present in up to 80% of patients at diagnosis 2
• Result from increased osteoclastic activity with suppressed osteoblastic function
• Require >30% trabecular bone loss to become visible on conventional radiographs 3
• Most commonly affect the skull, spine, ribs, pelvis, and proximal long bones

Critical Diagnostic Limitation

Conventional radiography has poor sensitivity for early bone destruction—lytic lesions only become visible after 30% or more of cortical bone is destroyed 4, 3. This is why modern guidelines now recommend:

• Whole-body low-dose CT (WBLD-CT) as the preferred initial imaging for suspected myeloma, as it detects lesions as small as 3-5mm 2, 3
• MRI for detecting bone marrow involvement before cortical destruction occurs 4
• PET/CT for evaluating extramedullary disease and treatment response 3

Differential Diagnosis

While punch-out lesions are classic for myeloma, other conditions can produce similar appearances:

Malignant Causes

• Metastatic disease (breast, lung, kidney, thyroid)
• Solitary plasmacytoma (single lesion before progression to myeloma) 4
• Langerhans cell histiocytosis (especially in children <5 years) 5

Benign Causes

• Intraosseous ganglia (typically solitary, carpus/wrist location) 6
• Erdheim-Chester disease (though typically shows sclerotic rather than lytic lesions) 7

Infectious Causes

• Brucella canis discospondylitis in dogs shows characteristic "hole punch" vertebral lesions 8
• Chronic osteomyelitis (though usually with surrounding reactive bone)

Clinical Approach When Punch-Out Lesions Are Identified

Age-Based Algorithm

For patients <40 years:

• Consider primary bone malignancy (sarcoma) or Langerhans cell histiocytosis
• Refer to orthopedic oncologist before further workup 9

For patients ≥40 years:

• First priority: Rule out metastatic disease
  • Serum protein electrophoresis (SPEP) and free light chains
  • CBC, comprehensive metabolic panel, calcium
  • CT chest/abdomen/pelvis
  • Bone marrow biopsy if myeloma suspected 2, 3

Myeloma-Specific Workup

When multiple punch-out lesions suggest myeloma:

1. Laboratory confirmation:

   • Serum and urine protein electrophoresis
   • Serum free light chain ratio (kappa/lambda) 1
   • Bone marrow aspirate and biopsy with flow cytometry 4

2. Imaging upgrade:

   • WBLD-CT is now standard (Grade 1A recommendation) 2, 3
   • Whole-body MRI if WBLD-CT shows no lytic disease but clinical suspicion remains 2
   • PET/CT for response assessment and extramedullary disease 3

Common Pitfalls to Avoid

• Do not rely solely on skeletal survey in suspected myeloma—it misses up to 80% of lesions detected by modern imaging 3
• Do not assume solitary lesions are benign—always exclude additional occult lesions with advanced imaging before diagnosing solitary plasmacytoma 4
• Do not overlook skull and rib lesions—these are better seen on plain radiographs than on WBLD-CT or MRI, so targeted views may still be needed 3

Treatment Implications

The presence of punch-out lesions in myeloma indicates:

• Active bone disease requiring bisphosphonate therapy (zoledronic acid or pamidronate) 2
• High risk for skeletal-related events (pathologic fractures, spinal cord compression)
• Need for systemic antimyeloma therapy to prevent progression 3
• Consideration for radiotherapy, kyphoplasty, or surgery for symptomatic lesions or impending fractures 2