How can I determine if a skin lesion is cancerous?

Determining if a Skin Lesion is Cancerous

For any suspicious pigmented lesion, perform complete excision with a 2 mm margin of normal skin using a scalpel—never rely on partial biopsy, laser, or electrocautery, as these compromise histological assessment and can lead to misdiagnosis. 1, 2, 3

Clinical Assessment Framework

Visual Examination Technique

Use the ABCDE rule to identify concerning melanocytic lesions: 1

• Asymmetry in shape
• Border irregularity
• Color variation (non-uniform pigmentation)
• Diameter greater than 6 mm
• Evolution (progressive change in size, shape, or color over time) 3

Alternatively, apply the "ugly duckling" sign: identify pigmented lesions that appear distinctly different from the patient's other moles. 1

Major Warning Signs Requiring Action

Any lesion with these features mandates referral or excision: 4, 3

• Progressive change in size 3
• Change in shape or color 4
• Regional lymph node enlargement (particularly preauricular and cervical nodes, which suggest nodal metastasis) 3

Complete Physical Examination

Perform a systematic evaluation including: 3

• Full-body skin survey covering the entire skin surface including scalp 1, 3
• Palpation of all regional lymph nodes to detect potential metastatic spread 1, 3
• Assessment for additional primary lesions (patients may have multiple skin cancers) 1

Diagnostic Pitfalls and Mimickers

Melanoma is phenotypically diverse and can be confused with: 1, 2

• Benign nevi
• Seborrheic keratoses 1, 2, 4
• Pigmented basal cell carcinomas 2
• Hematomas
• Vascular growths 1, 2

This diagnostic complexity underscores why complete excision is superior to clinical assessment alone. 1

Biopsy Technique: Critical Standards

Why Complete Excision is Mandatory

Never perform partial biopsy of suspected melanocytic lesions for these reasons: 1, 2

• Risk of misdiagnosis when only part of the lesion is examined 1
• Cannot assess maximum tumor thickness (Breslow depth)—the strongest prognostic factor 1, 3
• Cannot determine adequate margin clearance 1
• If benign, no further treatment needed; if malignant, complete assessment guides re-excision 1

Proper Excision Technique

• Use a scalpel only—never laser or electrocautery, as tissue destruction compromises diagnosis and histological prognostic assessment 1, 3
• Excise with 2 mm margin of normal skin 1, 2, 3
• Create an elliptical incision with long axis parallel to skin lines to facilitate potential re-excision with minimal skin loss 1
• Document excision margins in the operative note 1
• Send all specimens for standard histological examination (frozen sections are discouraged) 1

Essential Histopathology Requirements

The pathology report must include: 1, 3

• Confirmation of melanocytic nature and malignancy 1, 3
• Breslow thickness (maximum tumor thickness in millimeters)—the most important prognostic factor 1, 3
• Clark level of invasion 1, 3
• Assessment of complete excision of invasive and in situ components with microscopic measurement of clearance 1
• Presence and extent of ulceration 1, 3
• Presence and extent of regression 1

When Screening is Insufficient

The 2023 USPSTF guideline concludes that evidence is insufficient to recommend routine visual skin examination screening in asymptomatic adults without risk factors, as the balance of benefits and harms cannot be determined. 1 However, this applies only to population-level screening—symptomatic patients or those with suspicious lesions require immediate evaluation and biopsy. 1, 5

Additional Diagnostic Considerations

For isolated suspicious lymph nodes, fine-needle aspiration cytology can aid diagnosis, but definitive diagnosis requires histopathological examination of tissue. 3 Ultrasonography of regional lymph nodes is indicated when clinical uncertainty exists. 1, 3

Always biopsy suspicious lesions—a new or unusual skin lesion may represent primary skin cancer, internal malignancy, or cutaneous metastasis. 5, 6