Lentigo Maligna

Review of Salient Characteristics and Management

Joseph R. Kallini; Supriya K. Jain; Amor Khachemoune

Disclosures

Am J Clin Dermatol. 2013;14(6):473-480. 

In This Article

5 Treatment Options

If untreated, lentigo maligna poses the risk of dermal invasion and progression to invasive lentigo maligna melanoma. The percentage of lentigo maligna cases that progress to lentigo maligna melanoma has been estimated to be as low as 5 % and as high as 50 %.[22] Surgical excision remains the preferred treatment for lentigo maligna, but the methods by which excision is undertaken have evolved significantly. The alternatives for individuals with contraindications to surgical excision have also significantly expanded. A proposed therapeutic algorithm for the management of lentigo maligna is outlined in Fig. 5.

Figure 5.

Treatment of lentigo Maligna
Abbreviations: ED&C, electrodessication and curettage; MMS, Mohs micrographic surgery
aThese include patients who are elderly, large unresectable lesions of the head and neck, and problematic reconstruction.

5.1 Surgical Modalities

The challenge of excising lentigo maligna is to achieve complete tumor-free margins but with an optimal cosmetic outcome, especially with lesions on the face, head, and neck. Standard excision is insufficient in 50 % of cases.[23] Indeed, the mean total surgical margin required for tumor-free excision is 7.1 mm, suggesting that standard 5 mm surgical margins are inadequate.[24] This large average defect size is likely exacerbated by multiple prior treatments of lesions that interfere with adequate delineation of margins.[25] Multiple surgical techniques have been proposed.

5.1.1 Mohs Micrographic Surgery. Mohs micrographic surgery is a technique that differs from conventional surgical excision because it allows real-time in-clinic assessment of tissue samples. After the Mohs surgeon excises the cancer, the sample is immediately frozen, sectioned (horizontally rather than vertically), and assessed. If the margins of the sample are not clear, the surgeon excises more tissue in subsequent stages until the sample is tumor free. This technique allows a primary tumor mass to be excised completely with minimal loss of normal tissue, as with the patient shown in Fig. 6, who presented to our clinic. Mohs micrographic surgery is reported to have better cure rates than standard excision. While the recurrence rate after standard excision ranges from 8 to 20 %, the rate after staged Mohs micrographic surgery is only 4–5 %.[23]

Figure 6.

Lentigo maligna prior to Mohs micrographic surgery. 1–2 mm margins were delineated about the lesion. This tumor was successfully cleared after one stage

5.1.2 Geometric Staged Excision. Geometric staged excision has an even lower recurrence rate than Mohs micrographic surgery (1.7 %) and allows for complete examination of the peripheral and deep margins of excised specimens. In this technique, a Wood's lamp is used to demarcate the lesion margins. A geometric shape with at least three sides and with a 3–5 mm margin is then drawn around the lesion. Ninety-degree vertical incisions extending to the hypodermis are made along the drawn margins. The geometric shape is then excised, mapped, inked, and sent to the laboratory. The patient is sent home with pressure dressings. When the analysis of the sample is complete, the patient returns to the clinic. If the margins are not clear, additional stages with 3–5 mm margins are taken. If the sample is tumor free, the defect is repaired.[26]

5.1.3 The Spaghetti Technique. The spaghetti technique consists of three phases. In phase I, a 2 mm-wide strip of skin (the 'spaghetti') that circumscribes the lentigo maligna lesion is excised with 3–5 mm margins. The strip-like linear defect is immediately sutured together. The 'spaghetti' strand is then analyzed by dermatopathology. The patient returns at a later date once the results are available. If positive, an additional circumferential 'spaghetti' strand is removed with an extra 5 mm margin, followed by closure of the linear defect. The steps are repeated until the final strand is tumor free. Phase II involves resection of the lesion about the outermost peripheral sutured area. The surgeon will subsequently determine the method of reconstruction (via a graft or flap).[27]

Unlike Mohs micrographic surgery, the 'spaghetti technique' does not require specific training of surgeons or pathologists. Its advantage over geometric staged excision is not leaving patients with an open defect for days between visits before final reconstruction. Furthermore, this technique is very tissue sparing. In one study, the mean margin to clearance of lentigo maligna after excision was only 6.6 mm, and in a mean follow-up period of 15-months, 98.3 % of patients had no local recurrence.[27]

5.1.4 Special Considerations. It is important to emphasize that standard surgical excision may fail to completely resect the invasive component of lentigo maligna in at least half of all cases. Although standard surgical excision may be insufficient in half of all cases, imaging modalities such as digital epiluminescence microscopy and confocal microscopy have greatly improved outcomes.[28] Confocal microscopy is an imaging modality in which lesions visualized through a microscope are amplified and analyzed so that a two- or three-dimensional image is constructed. This allows lesions to appear with greater resolution and depth. In one study, confocal microscopy was able to detect subclinical disease in 59 % of patients with lentigo maligna lesions that extended beyond the standard 5 mm surgical margin. This changed the management in 73 % of these patients.[29] In instances where residual components remain after standard excision, non-surgical imaging modalities—including medical and destructive—play a strong role.

5.2 Medical Modalities

Surgical excision is the gold standard in the treatment of lentigo maligna. However, non-surgical modalities can be used for a subset of patients. Imiquimod, a topically applied immunomodulator, stimulates toll-like receptors 7 and 8, which enhances innate and acquired immune responses. This leads to activation of nuclear factor jB, which galvanizes the production of inflammatory cytokines such as tumor necrosis factor a, interleukin 12, interferon a, and interferon c. In addition, cytotoxic T cells are activated, which induce apoptosis in tumor cells.[30] There is no consensus regarding the dosage of imiquimod. The dosage varies from daily to three times weekly for between 2 weeks and 7 months. Although this modality is cosmetically favorable, 12 % of patients in one study had recurrence or no response.[31] In fact, some cases of lentigo maligna treated with imiquimod have progressed to invasive malignant melanoma with satellite lesions.[32] Another disadvantage of topical therapy is the inability to determine tumor resolution with complete certainty. Although surgical excision is cosmetically unfavorable, it allows for histological confirmation of tumor-free margins.

5.3 Radiotherapy

Radiotherapy is a locally destructive technique best used for elderly patients, patients with large facial and neck lesions, patients in whom reconstruction may be problematic, and patients who have a residual tumor after surgical excision. One study of soft X-irradiation treatment of lentigo maligna demonstrated complete resolution in only 88 % of patients.[33] In Toronto, Canada, 86 % of patients treated with radiotherapy had no local recurrence within 5 years.[34] In another review, 14 out of 17 patients with lentigo maligna treated with radiation had no recurrence within 5 years.[35] In the latter two studies, multifractionated radiation at 100–280 kV was delivered at a 5–6 mm depth. One study at the University of Munich in Germany used a direct field superficial X-ray with a total of 100 Gy applied over 10 fractions at a depth of 1.1 mm. Of the 42 patients with lentigo maligna, none had recurrence of the tumor within a mean 23-month follow-up period. Complications included hypo- and hyperpigmentation.[36] Nevertheless, radiation serves as a good alternative for patients in whom surgery is not preferred.

5.4 Other Modalities

Other modalities for the treatment of lentigo maligna include laser ablation, cryotherapy, and curettage and electrodessication. Carbon dioxide laser should be used only if excision is contraindicated (as in elderly patients with concomitant medical conditions) and if the lentigo maligna lesion has not progressed to lentigo maligna melanoma.[37] Cryotherapy, electrodessication, and other destructive methods are rarely used to treat lentigo maligna, because of their inability to deeply penetrate to periadnexal melanocytes as well as the lack of biopsyconfirmed tumor removal.[38]

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