Basics of Dermatology Morphology
Understanding the fundamental morphological characteristics of skin lesions is essential for accurate diagnosis and treatment of dermatological conditions. 1
Primary Lesion Types
- Macules: Flat, non-palpable changes in skin color less than 0.5 cm in diameter 2
- Patches: Flat, non-palpable changes in skin color greater than 0.5 cm in diameter 2, 3
- Papules: Raised, palpable solid lesions less than 0.5 cm in diameter 2, 3
- Plaques: Raised, flat-topped, palpable lesions greater than 0.5 cm in diameter 2, 3
- Nodules: Firm, raised lesions that extend deeper into the dermis 3
- Cysts: Encapsulated fluid-filled lesions 3
- Vesicles: Raised, fluid-filled lesions less than 0.5 cm in diameter 3
- Bullae: Raised, fluid-filled lesions greater than 0.5 cm in diameter 3
- Pustules: Visible collections of pus within the skin 3
- Wheals: Transient, edematous, erythematous papules or plaques 3
Surface Features
- Scale: Visible accumulation of keratin 2
- Crust: Dried serum, blood, or exudate on the skin surface 2
- Erosion: Loss of epidermis not extending into dermis 3
- Ulcer: Loss of epidermis and at least part of the dermis 3
- Excoriation: Linear erosion caused by scratching 3
- Atrophy: Thinning of the skin 3
- Smooth/Normal: Absence of surface changes 2
Lesion Assessment Framework
1. Location and Distribution
- Site: Specific anatomical location 2
- Distribution: Pattern of lesion spread (e.g., symmetric, asymmetric, localized, generalized) 2
- Arrangement: How lesions are organized (e.g., linear, annular, grouped) 2
2. Morphological Characteristics
- Palpation: Texture and consistency when touched 2
- Type: Primary lesion classification 2, 3
- Surface: Presence of scale, crust, erosion, etc. 2
- Color: Pigmentation and hue 1
- Border: Edge characteristics (e.g., well-defined, irregular) 1
- Size: Measured dimensions 2
- Shape: Geometric configuration 2
3. Associated Features
- Nail changes: Pitting, discoloration, thickening 2
- Mucosal involvement: Lesions affecting mouth, genitals 2
- Hair abnormalities: Changes in hair density or texture 2
Diagnostic Approach for Pigmented Lesions
The ABCDE criteria are particularly useful for evaluating potentially malignant pigmented lesions 1:
- A: Asymmetry
- B: Border irregularity
- C: Color heterogeneity
- D: Diameter >6mm
- E: Evolution (recent change)
Some clinicians also use the "three change criteria" (changes in size, color, and shape) or the "seven criteria" approach (three major: changes in size, color, shape; four minor: diameter >7mm, hypersensitivity, bleeding, inflammation) 1.
Advanced Diagnostic Techniques
- Dermatoscopy/Epiluminescence Microscopy (ELM): Non-invasive technique that improves clinical diagnosis by differentiating melanocytic from non-melanocytic lesions 1
- Reflectance Confocal Microscopy (RCM): Allows visualization of skin at near-histological resolution 1
- Biopsy: Gold standard for definitive diagnosis of suspicious lesions 1
Common Pitfalls in Morphological Assessment
- Inconsistent terminology: Using non-standardized terms leads to communication errors 3
- Incomplete examination: Failing to assess all characteristics of a lesion 2, 4
- Overlooking distribution patterns: Missing diagnostic clues from lesion arrangement 2
- Inadequate lighting and magnification: Proper conditions are essential for accurate assessment 1, 4
- Failure to document evolution: Not tracking changes in lesions over time 1
Training Recommendations
- Systematic approach: Follow a structured framework for lesion description 2, 4
- Pattern recognition training: Use Perceptual and Adaptive Learning Modules (PALMs) to improve identification skills 4
- Regular practice: Consistent exposure to diverse dermatological presentations 4
- Technology integration: Utilize AI-assisted tools as adjuncts to clinical assessment 5