Purple, Symmetrical, Flat Lesion on the Antihelix: Clinical Description and Differential Diagnosis
This lesion most likely represents a benign vascular malformation (such as a capillary malformation/port-wine stain) or a traumatic hematoma, given its purple color, flat morphology, symmetry, small size (<1 cm), and regular borders on the antihelix.
Key Descriptive Features
The lesion can be characterized using standardized terminology:
- Color: Purple pigmentation suggests vascular origin (blood vessel proliferation or extravasated blood) or melanocytic pathology 1
- Morphology: Flat (macular) presentation without elevation rules out nodular processes 1
- Size: Less than 1 cm diameter places this in the small lesion category, which has different diagnostic implications than larger lesions 1
- Borders: Regular, well-defined borders suggest a benign process rather than infiltrative malignancy 1
- Symmetry: Bilateral symmetry is reassuring against malignancy, as melanoma typically presents with asymmetry 1
- Location: Antihelix of the ear is an exposed anatomical site subject to trauma and sun exposure 1
Primary Differential Diagnoses
Most Likely: Benign Vascular Lesion
- Capillary malformation (port-wine stain): Purple, flat, well-demarcated vascular lesion that can occur on the ear 2
- Traumatic hematoma: Purple discoloration from blood accumulation in tissue, particularly if there is history of trauma 2
- Venous lake: Small, compressible, purple-blue vascular lesion common on sun-exposed areas including ears 2
Less Likely but Important to Exclude
Melanoma considerations: While the described features (symmetry, regular borders, flat, <1 cm) are atypical for melanoma, any pigmented lesion on sun-exposed skin warrants careful evaluation 1. However, melanoma typically violates the ABCDE rule with Asymmetry, Border irregularities, Color heterogeneity, Diameter >6 mm, and Evolution 1. This lesion's symmetry and regular borders argue strongly against melanoma 1.
Recommended Diagnostic Approach
Initial Clinical Assessment
- Dermoscopy: Can help differentiate vascular from melanocytic lesions and identify specific patterns 1
- Compression test: Vascular lesions typically blanch with pressure, while melanocytic lesions do not 2
- History: Inquire about trauma, duration, changes over time, and symptoms (pain, bleeding, pruritus) 1
Biopsy Indications
Excisional biopsy with 1-3 mm margins is recommended if there is any diagnostic uncertainty, particularly to exclude melanoma 1. For lesions on the ear, full-thickness incisional or punch biopsy is acceptable given the anatomical constraints 1.
The biopsy should be performed if:
- The lesion shows any evolution in size, color, or elevation 1
- Dermoscopy reveals concerning features 1
- Clinical diagnosis remains uncertain after initial assessment 1
Pathology Requirements
If biopsy is performed, the pathology report must include 1:
- Full thickness assessment (Breslow thickness if melanoma suspected)
- Presence or absence of ulceration
- Margin status
- Histologic subtype and specific diagnosis
Management Based on Diagnosis
If Benign Vascular Lesion Confirmed
- Observation: Most benign vascular lesions require no treatment 2
- Laser therapy: Can be considered for cosmetic concerns 2
- Reassurance: Patient education about benign nature 2
If Melanoma Cannot Be Excluded
Complete excision with appropriate margins is mandatory 1:
Critical Pitfalls to Avoid
- Never dismiss a pigmented lesion on the ear without proper evaluation, as the ear is a cosmetically important and sun-exposed site where melanoma can occur 1
- Do not perform shave biopsy if melanoma is in the differential, as this may compromise Breslow thickness assessment 1
- Avoid observation alone if there is any clinical suspicion for malignancy, even in small lesions 1
- Do not delay biopsy based solely on small size, as early melanomas can present as small lesions 1