A 56-year-old man presented with complaint of lifelong history of darkening, growing left lesion of the left cheek. Biopsy on 09/24/21 showed melanoma in-situ. Excision with 5-6mm margins and closure of left cheek melanoma performed on 12/2/21 showed positive margins at 3-4 o’clock margins. Woods lamp evaluation and re-excision performed on 1/7/22.
Lentigo maligna melanoma is a subset of melanoma in situ characterized by vague margins and extensive spread. While the traditional melanoma in situ can be surgically removed with 7 or greater mm margins, the lentigo maligna type margins are difficult to assess. Several treatment strategies are available for lentigo maligna melanoma in situ.
Radiation treatment requires once a day treatments 3 to 5 days per week for 2-4 weeks. Treatment success of melanoma in situ and lentigo maligna with radiation is variable, with recurrences in the range of 10%. Recurrences depend on field margins and energies used. In addition, once irradiated, you may not radiate the same area twice, eliminating radiation as a future treatment for the patient.
The discussion of IHC stains involved the Preferentially expressed Antigen in Melanoma (PRAME). PRAME has been increasingly used for evaluation of pigmented lesions to determine the likelihood of melanoma. If PRAME positive, the lesion is highly suspicious for melanoma. However, these stains are not foolproof, as positive PRAME results are seen in actinic keratoses (AK). Therefore, clinical correlation is imperative when interpreting PRAME positive results.
Mohs for lentigo maligna has been controversial but has gained greater popularity. A recent study by Sharma et al (2021) compared the success of Mohs for the treatment of lentigo maligna with traditional excision with rapid FFPE (formalin fixed paraffin embedded processing) finding an improved recurrence rate as low as 1.35% with Mohs surgery. They concluded that Mohs surgery is one of the most successful treatment options for lentigo maligna.
When deciding surgical vs radiation, it’s important to consider multiple factors, such as the patient’s level of activity, quality of life, likelihood of additional cancers in the same region, and availability of reconstructive options.
SCARS Center recommended excision with 5-6 mm margins which was sent for permanent pathology for this patient. Unfortunately, the margins were positive, as can be the case with lentigo maligna type, and a second excision was needed.
Sharma AN, Foulad DP, Doan L, Lee PK, Atanaskova Mesinkovska N. Mohs surgery for the treatment of lentigo maligna and lentigo maligna melanoma – a systematic review. J Dermatolog Treat. 2021 Mar;32(2):157-163. doi: 10.1080/09546634.2019.1690624. Epub 2019 Nov 20. PMID: 31696746.
Hendrickx, A., Cozzio, A., Plasswilm, L. et al. Radiotherapy for lentigo maligna and lentigo maligna melanoma – a systematic review. Radiat Oncol 15, 174 (2020). https://doi.org/10.1186/s13014-020-01615-2