What does the ABCDE (Asymmetry, Border, Color, Diameter, Evolving) of melanoma stand for?

ABCDE of Melanoma

The ABCDE rule is a clinical mnemonic for identifying suspicious pigmented lesions: Asymmetry, Border irregularities, Color heterogeneity, Diameter (historically >6mm, though many melanomas are now <5mm), and Dynamics/Evolution (changes in colors, elevation, or size over time). 1

Components of the ABCDE Rule

A - Asymmetry

• Asymmetry of contour refers to one half of the lesion not matching the other half when divided through the center 1
• Present in approximately 65% of melanomas, though notably absent in 35% of cases 2

B - Border Irregularities

• Border irregularity describes uneven, notched, or scalloped edges rather than smooth, round borders 1
• Regular borders are found in 12% of melanomas, making this criterion imperfect 2

C - Color Heterogeneity

• Color variegation means multiple colors or uneven distribution of pigmentation within a single lesion 1
• Color variation is present in only 63% of melanomas 2
• Unevenness in distribution of colors and textures is actually present in 94% of melanomas and may be a more sensitive criterion than simple color variegation 2

D - Diameter

• Diameter greater than 6mm was the traditional threshold 1
• Critical caveat: Many primary melanomas today have a diameter of <5mm, making this criterion less reliable 1
• Approximately 28% of melanomas are small (<6mm in diameter) 2

E - Evolution/Dynamics

• Evolution refers to changes in colors, elevation, or size over time 1
• This is a very important criterion because it can help identify rapidly growing amelanotic melanomas in educated patients 1
• History documenting morphologic change over time is an important additional consideration, especially for early invasive and in situ melanomas 3

Clinical Application and Important Caveats

Limitations of ABCDE

• The ABCDE rule is not foolproof: Some melanomas lack all or most of these features, particularly early invasive and in situ melanomas 3
• Dermatologists' diagnostic accuracy relies more on unconscious cognitive processes (overall pattern recognition) and comparative processes (ugly duckling sign) rather than strict ABCD algorithm analysis 4

Complementary Diagnostic Approaches

• The "ugly duckling" concept identifies melanomas because nevi in the same individual tend to resemble one another, and melanomas often do not fit the individual nevus pattern 1
• Dermoscopy by an experienced physician enhances diagnostic accuracy beyond clinical examination alone 1

When to Biopsy

• Maintain a low threshold for biopsy of unusual lesions that do not show typical benign features, even if they do not meet all ABCDE criteria 3
• Diagnosis should be based on full thickness excisional biopsy with a minimal side margin when melanoma is suspected 1