Lentigo malignaD03.-

In actinically damaged skin, slowly growing (non-invasive) melanoma (in situ melanoma). This melanoma is a lesion of old age and occurs almost exclusively in sun-exposed areas (face, back of the hands, extensor sides of the forearms). The transition to an invasive growing lentigo-maligna melanoma is manifested by a palpable elevation. Histological clarification by staged sections and confirmation of the precise tumor stage (pTis = melanoma in situ, Clark level I) is mandatory.

In a Danish study (2014), an increase in the "age-adjusted percentage change" incidence rate from 1997-2011 from 2.6 to 8.1 cases/100,000 for women and from 1.4 to 5.6/100,000 for men was demonstrated. These figures refer to both lentigo maligna and the precursor stage of SSM.

Preferred population > 50 years. w > m

Integument: Solitary, brown or blackish-brown, roundish-oval or bizarre, peripherally growing, (not palpable) inhomogeneous spot or patch of varying colour intensity; often with polycyclic or reticulated, sharp or blurred edges.

Reflected light microscopy: Highly irregular, prominent pigmentary net with breaks in the periphery.

Also visible are spots of diffuse pigmentation, central and peripheral black dots, possibly also irregularly limited depigmentation and a delicate grey cast.

• Verruca seborrhoica: Colour pattern may resemble the lentigo maligna. Mostly horn beads are detectable by reflected light microscopy. In case of doubt, a biopsy is decisive.
• Lentigo solaris: Less pigmented, homogeneous or inhomogeneous brown spot with mostly blurred edges. Transitions to lentigo maligna can be fluid.
• Melanoacanthoma: Deep black plaque not preferentially occurring in sunlight-exposed areas. Histological clarification.
• Pigmented basal cell carcinoma: Irregularly pigmented plaque; typical BCC criteria are usually detectable by incident light microscopy.
• pigmented Bowen's disease. Mostly sharply edged, irregularly configured plaque (no stain) with a rough surface.

Therapy of first choice is the (micrographically controlled) excision of the lesion with a (possible) safety margin of 0.5 cm. Here, a serial histological processing of the peripheral areas is an absolute prerequisite. The reported recurrence rates are between 0 and 6.25%. 85% of all dermatologists prefer excision as the method of choice in patients <60 years of age, 87% in patients between 60-70 years of age, 67% in patients > 70 years (Thio D et al. 2018).

Alternative cryosurgery: particularly indicated for larger foci in the facial area, whose surgery would result in a disfiguring scar. It may also be an option for patients of advanced age. The closed contact method with 2 cycles is recommended. In case of the open spray method a moulage has to be applied (25% of dermatologists use this method).

Alternative radiotherapy: especially indicated for patients > 70 years. Carried out with Dermopan (Siemens) or R.T. 100 (C. H. Müller, Hamburg) with a tube voltage up to 12 kV (borderline radiotherapy; GHWT 1.3 mm). Use 4-5 times 20 Gy in 2-day intervals (procedure is recommended by 27% of dermatologists).

Alternatively Imiquimod: currently widely used procedure (50% of all dermatologists use this therapeutic approach). In particular, the use of Imiquimod is indicated in patients > 70 years of age with significant limitations in operability. Local treatment with 5% Imiquimod cream (e.g. Aldara®) for 5-6 weeks (3 times/week, left for 12 hours). Recurrences or therapy failure were observed (27.5% residual lentigo maligna - results of a 5-year follow-up study; Kai AC et al. 2016). Furthermore, progressions with development of lentigo maligna melanoma were reported after completion of therapy.

According to the malignant melanoma, initial control of the local findings every 3 months (period 1 year); later larger intervals. S.u. melanoma, malignant.

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2. Elsner Pet al (2014) Lentigo maligna and lentigo maligna melanoma as occupational skin diseases in a forestry worker with long-standing occupational UV exposure. J Dtsch Dermatol Ges 12:915-917
3. Epstein E (2003) Extensive lentigo maligna clearing with topical imiquimod. Arch Dermatol 139: 944-945
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    : a survey study among European Association of Dermatologists andVenereologists
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