How do you localize a lesion?

Lesion Localization Techniques in Clinical Practice

For accurate lesion localization, create a session map with appropriate imaging techniques and anatomical landmarks, documenting the exact location relative to fixed reference points. 1

Imaging-Based Localization Methods

Reflectance Confocal Microscopy (RCM) for Cutaneous Lesions

• Always create a session map to document the location of each image relative to the dermatoscopic image 1
• For lesions >8mm requiring multiple imaging placements:
  • Create a session map for each placement
  • Provide a supplementary diagram on a photograph of the lesion showing locations of each placement 1
• Center the first image set on the portion with the largest diameter, considering mosaic size of 8mm² 1
• Ensure minimum 10% overlap between each basic image set 1
• Include adjacent non-lesional skin in at least one of the basic image sets for comparison 1

Endoscopic Localization for Gastrointestinal Lesions

• For lesions requiring future localization, use tattoo marking with commercially available inert injection agents 1
• Place tattoos at 2-3 separate locations 3-5cm distal (anal side) to the lesion 1
• Create tattoos at least 2cm away from the lesion to avoid submucosal fibrosis that could complicate future endoscopic resection 1
• Document the orientation of tattoos in relation to the lesion in the procedure report 1
• For surgical referral, place tattoos in line with and on the opposite lumen wall from the lesion 1

MRI for Neurological Lesions

• Use gadolinium contrast enhancement (0.1 mmol/kg IV) to improve lesion border delineation, internal morphology visualization, and contrast enhancement 2
• For suspected cerebral metastases, consider additional 0.2 mmol/kg dose which improves visualization in 67% and border definition in 56% of patients 2
• Document lesion location relative to anatomical landmarks such as ventricles, cortex, and subcortical structures 3
• For white matter lesions, note their relationship to ventricles (periventricular), cortex (juxtacortical), or subcortical regions 3

Anatomical Landmark-Based Localization

Neurological Lesion Localization

• For cranial nerve lesions (e.g., third nerve palsy), document associated neurological signs to help localize the lesion 1, 4:
  • Lesions involving superior cerebellar peduncle: look for ipsilateral cerebellar ataxia 4
  • Lesions involving red nucleus: look for ipsilateral flapping hand tremor and ataxia 4
  • Lesions involving cerebral peduncle: look for ipsilateral hemiplegia or hemiparesis 4
• Use network localization approaches for symptoms that don't localize to a single region 5, 6

Gastrointestinal Lesion Localization

• For colonic lesions, document location in relation to fixed anatomic structures (appendiceal orifice, ileocecal valve, anal verge) 1
• Tattoos may be unnecessary if lesions are in close proximity to clear anatomic landmarks such as cecum, ileocecal valve, or rectum 1

Cutaneous Lesion Localization

• For non-flat lesions or those on contoured body sites:
  • Begin mosaics at the top of the most elevated lesion area 1
  • Capture additional mosaics to document each anatomic level throughout the entire lesion 1
  • Reset depth measurements at the surface of the corneal layer in less elevated portions 1

Special Considerations

For Ulcerated, Crusted, or Eroded Lesions

• Image with caution as these features can cause significant backscatter of light 1
• If ulcer/crust/erosion covers >20% of the lesion, capture additional images at the erosion's border 1
• For lesions with >50% ulceration/crusting/erosion, proceed directly to biopsy as imaging may miss diagnostic information 1

For Thickened/Raised Lesions

• Adjust mosaic cube settings: increase depth of first mosaic and spacing between mosaics 1
• Capture 4 representative mosaics with good resolution at different depths 1
• Consider including a 5th mosaic with decreased resolution to capture deeper architecture 1

Common Pitfalls and How to Avoid Them

• Inadequate documentation: Always create detailed maps showing lesion location relative to anatomical landmarks 1
• Improper tattoo placement: Place tattoos 3-5cm from the lesion to avoid interfering with subsequent endoscopic removal 1
• Missing network effects: Consider that symptoms may stem from dysfunction in regions connected to the lesion site rather than the site itself 5, 6
• Incomplete imaging: For large lesions (>8mm), ensure adequate coverage with multiple overlapping images 1
• Failure to include normal tissue: Always include adjacent non-lesional tissue in at least one image for comparison 1

By following these structured approaches to lesion localization, clinicians can ensure accurate documentation and facilitate appropriate treatment planning, ultimately improving patient outcomes.