Published on 18/03/2015 by admin
Filed under Dermatology
Last modified 18/03/2015
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Darrell S. Rigel, Ellen S. Marmur and John A. Carucci
Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports
Lentigo maligna (LM) is a type of melanoma in situ that classically presents as irregular pigmented patches on sun-exposed areas of the face and neck in older individuals. If left untreated, the lifetime risk of LM progressing to invasive melanoma (lentigo maligna melanoma, LMM) varies from 4.7% to 2.2%. LM and LMM are the most common forms of melanoma on the head and neck, are commonly found on the cheek, often present as a cosmetic concern, and their incidence is increasing. Treatment has been difficult owing to high recurrence rates, which are attributed to subclinical extension and the difficulty of determining tumor margins.
The first treatment of choice for LM is wide local excision with a margin of at least 5 mm, which leads to clearance rates of 24–70% and recurrence rates of 7–20%. Staged surgical excision is associated with recurrence rates of 0% to 9.7%. In some patients, surgical treatment will inevitably lead to large skin defects and complex surgical reconstructions. Combination therapy with both surgical and non-surgical modalities, and surgery with wider margins are at the forefront of research in the field of LM/LMM.
Successful management of LM depends on early diagnosis and definitive removal. The differential diagnosis includes lentigo, macular seborrheic keratosis, pigmented actinic keratosis, pigmented squamous cell carcinoma in situ, and pigmented superficial basal cell carcinoma. Confirmatory biopsy is necessary prior to definitive treatment. The use of a Wood’s lamp may help to determine the perimeter of the lesion. Dermoscopy may also be helpful. Biopsy of the entire lesion is ideal in order to ascertain its maximum depth. However, the lesion tends to be large (>1 cm) owing to its propensity for extensive radial growth prior to vertical growth into the dermis. Therefore, biopsy of part of the lesion is often performed. Treatment is primarily surgical, although eradication by other methods may be considered. Patients with a history of LM should have periodic full-body skin examinations by a dermatologist to allow for early detection of recurrence, progression, or a second primary skin cancer. Patients with LM also require a consultation about sun protection behaviors.
Skin biopsy and patient evaluation
NIH Consensus Statement, 1992; 10: 1–26.
Biopsy of sufficient depth is critical for diagnosis and management of pigmented lesions. Punch, saucerization, excision, or incisional biopsy may be acceptable. On microscopic examination LM is characterized by increased numbers of atypical melanocytes, which may be solitary or arranged in nests, but do not invade the dermis. Evaluation should include a personal and family history, complete skin examination, and palpation of regional lymph nodes. Blood tests or imaging studies are not indicated.
NIH Consensus Statement 1992; 10: 1–26.
Current recommendations are based on the NIH consensus for melanoma in situ, which suggests excision of the lesion or biopsy site with a margin of 0.5 cm of clinically normal skin and layer of subcutaneous tissue. In general, margins of 0.5–1.0 cm are suggested for LM where feasible. Difficulties may arise in determination of clinical margins due to diffuse background sun damage. A Wood’s lamp may be useful in defining subclinical extension. Accurate determination of margins is key, because LM is likely to recur after inadequate excision.
Johnson TM, Headington JT, Baker SR, Lowe L. J Am Acad Dermatol 1997; 37: 758–64.
With this technique, a margin of 0.5–1.0 cm is outlined with angled corners to facilitate processing. A peripheral strip of tissue 2–4 cm wide is excised and processed for evaluation of permanent sections. Residual tumor is subsequently excised in directed fashion based on mapping. There were no recurrences in 35 patients at 2 years.
Cohen LM, McCall MW, Zax RH. Dermatol Surg 1998; 24: 673–7.
A report of successful treatment at 29.2 months in 45 patients with LM and LMM with Mohs micrographic surgery (MMS) aided by rush permanent sections. There was one recurrence at 50 months (97% cure rate).
Bene NI, Healy C, Coldiron BM. Dermatol Surg 2008; 34: 660–4.
Patients (n=116) with melanoma in situ (MIS) in sun-exposed skin of LMM type, were treated by MMS with subsequent evaluation of the final margin with paraffin-embedded sections that were cut en face, over a period of 12 years (mean follow-up, 50 months; median 48 months; 594.5 patient-years). The clearance rate by MMS technique using frozen sections was 94.1% for MIS LM type. The cure rate was 99.0% for MIS LM type.
MMS is a viable option for treatment of MIS that may increase cure rate and reduce the size of the defect especially in cosmetically and functionally sensitive areas.
Zalla MJ, Lim KK, Dicaudo DJ, Gagnot MM. Dermatol Surg 2000; 26: 771–84.
Treatment of Skin Disease Comprehensive Therapeutic Strategies 4e
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Excision
Mohs micrographic surgery
Modified Mohs surgery
Staged excision
