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STAGED EXCISIONS FOR LENTIGO MALIGNA

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SUMMARY

  • Lentigo maligna and lentigo maligna melanoma are very common in the elderly population.

  • Surgical approaches include Mohs surgery (relying heavily on immunohistochemical staining) and staged excisions.

  • Radiation therapy is particularly popular outside of the United States, while imiquimod may be better used as a neoadjuvant approach rather than monotherapy except in select patients.

  • The large margins often needed mean that surgery may have significant associated morbidity.

image Beginner Tips

  • Closing the excisional biopsy with a single or double purse string shrinks the size of the defect down to its smallest possible surface area.

  • After taking a stage for LM, a fascial plication suture and/or an intradermal traction suture can be left in place while the tissue is being processed. This allows the skin to relax along the RSTLs and facilitates the ease of closure when negative histologic margins have been confirmed.

image Expert Tips

  • The nuclear stains MiTF and SOX10 are less sensitive than MART-1/Melan-A, but are more specific as they do not stain dendritic processes or keratinocytes, and enable a much more accurate melanocyte density count.

image Don’t Forget!

  • The application of topical imiquimod 5% in the neoadjuvant setting for 5 days weekly for 2 to 3 months allows for the removal of over 90% of LM lesions with a conservative 2-mm margin compared to the average requirement of a 7.1-mm margin for cases of LM untreated with topical imiquimod.

  • The negative control allows for subtraction of the atypical junctional melanocytic hyperplasia common to chronically sun-exposed skin from the LM surgical margins and increased accuracy of concordance rates between dermatopathologists assessing surgical margins of LM specimens.

image Pitfalls and Cautions

  • SOX10 commonly stains eccrine cells and regenerating Schwann cells in scar tissue, so care must be taken to not falsely record dermal invasion in those cases.

image Patient Education Points

  • RT provides a gentler approach with better cosmetic outcomes, but may have a somewhat higher local recurrence rate and morbidity.

  • The low mortality risk of treated LM and its prevalence in the elderly population means that therapy should always be tailored to the individual patient and an extensive discussion regarding risks, benefits, and alternatives should always be undertaken.

image Billing Pearls

  • Coding for true Mohs for LM utilizes the 17311-2 series and 17313-4 series used for tumors of the head/neck/hands/feet/genitalia and all other areas, respectively.

  • Billing for immunohistochemical stains is in addition to standard Mohs layer billing, and is generally billed on a per-specimen basis with code 88342 for the first antibody followed by 88341 for each additional antibody. If multiple separately identifiable antibodies are applied to the slide, use one unit of 88344.

INTRODUCTION

Melanoma is divided into several categories based on clinical and histologic features, including superficial spreading, nodular, lentigo maligna melanoma (LMM), and acral lentiginous melanoma. Ocular melanoma ...

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