What is the diagnosis and treatment for melanoma in situ (stage 0 melanoma)?

From the Guidelines

Melanoma in situ is typically treated with wide local excision, removing the entire lesion along with a safety margin of at least 0.5 cm to ensure all cancer cells are removed, as recommended by the most recent guidelines 1. The goal of treatment is to completely remove the cancerous cells and prevent the progression to invasive melanoma.

• The standard approach involves surgical excision with a margin of normal-appearing skin around the tumor.
• Complete surgical removal is typically curative, with a nearly 100% survival rate, as supported by the NCCN guidelines 1.
• Following treatment, regular skin examinations are essential, including self-checks monthly and professional dermatological evaluations every 3-12 months depending on risk factors.
• Patients should practice sun protection by using broad-spectrum sunscreen (SPF 30+), wearing protective clothing, avoiding peak sun hours (10 AM to 4 PM), and avoiding tanning beds.
• Early detection and treatment are crucial as melanoma in situ can progress to invasive melanoma if left untreated, at which point it can spread to other parts of the body and become life-threatening.
• The NCCN guidelines also suggest that for certain subtypes of melanoma in situ, such as lentigo maligna and acral lentiginous type, surgical margins of 0.5 cm may be needed, and techniques such as Mohs micrographic surgery (MMS) and staged excision with formalin-fixed, paraffin-embedded (ie, permanent) sections may be used to improve histologic clearance and decrease the chance of local recurrence 1.
• It is worth noting that while topical imiquimod and radiotherapy have emerged as treatment options for certain cases of melanoma in situ, the evidence for these treatments is not as strong as for surgical excision, and long-term comparative studies are still needed 1.

From the Research

Diagnosis of Melanoma In Situ

• Melanoma in situ (MIS) is an early variant of melanoma in which the disease is limited to the epidermis 2
• Standard diagnosis is currently made through surgical excision with at least 5-mm margins, followed by histological assessment 2, 3

Treatment of Melanoma In Situ

• Current treatment recommendations for malignant melanoma in situ include surgical excision with at least 0.5 cm margins 4
• However, alternative topical therapy with imiquimod has been proposed in recent studies as a possible treatment for MIS 4, 2, 5
• Topical 5% imiquimod cream has been shown to be effective in treating MIS, with complete regression of the disease observed in some cases 4, 2, 5
• The use of topical imiquimod can be particularly useful in cases where surgical excision is not feasible or desirable, such as in elderly patients or in cases where the lesion is located in a cosmetically sensitive area 4, 2

Surgical Excision Margins

• The recommended excision margins for melanoma in situ are 5-10 mm 3
• However, the use of bread-loafing (serial cross-sectioning) may result in false negative margin examination and higher local recurrence rates than Mohs micrographic surgery, which histologically evaluates the entire surgical margin 6
• Complete histologic margin control of the entire surgical margin using en-face tissue orientation (Mohs technique) is recommended to reduce the risk of recurrence 6

Topical Imiquimod Treatment Regimens

• A 6-week course of topical 5% imiquimod cream has been shown to be effective in treating MIS, with a cure rate of 93.3% 2
• The treatment regimen can be titrated based on response, with the frequency and duration of treatment adjusted as needed 2, 5