Melanoma In Situ Diagnosis and Monitoring in London

Understanding melanoma in situ

Melanoma in situ is a pre-invasive form of skin cancer. Abnormal melanocytes (pigment cells) grow uncontrollably but remain confined to the epidermis. Because they have not yet invaded the dermis, the risk of spread is absent at this stage. This makes melanoma in situ a highly treatable condition with excellent prognosis when detected early.

Causes and risk factors

Melanoma in situ arises from DNA damage to melanocytes, usually triggered by ultraviolet (UV) light. Contributing factors include:

• Sun exposure: Chronic or intense sun exposure, especially sunburns.
• Skin type: Fair skin, freckles, and light hair increase risk.
• Multiple moles: Having many melanocytic naevi, particularly atypical ones.
• Family history: A close relative with melanoma raises personal risk.
• Weakened immunity: Immunosuppression increases susceptibility.

Melanoma Symptoms and appearance

Melanoma in situ can resemble a mole but usually looks unusual compared to others (“ugly duckling sign”). Warning features include:

• Asymmetry (one half different from the other)
• Irregular or blurred borders
• Multiple colours (brown, black, red, pink, grey)
• Increasing size or diameter above 6 mm
• Evolution — any recent change in colour, size, shape, or symptoms (itching, bleeding)

Melanoma Diagnosis

Diagnosis requires careful clinical evaluation and dermoscopy. If suspicious features are present, an excision biopsy is performed. Histological analysis confirms whether abnormal melanocytes are confined to the epidermis (in situ) or have invaded deeper layers.

Melanoma Treatment and management

The gold-standard treatment for melanoma in situ is surgical excision with a margin of normal skin. This ensures complete removal of abnormal cells and minimises recurrence risk. Other aspects of care include:

• Follow-up skin checks: Regular dermatology reviews to detect new lesions early.
• Sun protection: Daily sunscreen, protective clothing, and avoidance of tanning beds.
• Self-examination: Monthly skin checks using mirrors or photography to track changes.

Living with melanoma in situ

Most people treated for melanoma in situ have an excellent outlook. The key is vigilance: adopting sun-safe habits, keeping dermatology follow-ups, and seeking early review of new or changing skin lesions. Psychological support and reassurance are also valuable, as any cancer diagnosis can cause anxiety.

Your first visit — what to expect

1. History: Review of mole changes, sun exposure, and family history.
2. Examination: Full skin and mole assessment using dermoscopy.
3. Investigations: Excision biopsy of suspicious lesions.
4. Management plan: Surgical removal and advice on prevention and monitoring.
5. Follow-up: Ongoing skin checks and support for long-term skin health.

Reviewed by: Dr Mohammad Ghazavi, Consultant Dermatologist
Skinhorizon Clinic, 4 Clarendon Terrace, Maida Vale, London W9 1BZ
Last reviewed: 22 August 2025