lentigo maligna melanoma Flashcards
What is the definition of melanoma in situ (MIS)?
Melanoma confined to the epidermis without dermal invasion. Subtypes include lentigo maligna, superficial spreading in situ, and acral lentiginous in situ, among others.
Why does lentigo maligna (LM) often require wider margins than other forms of MIS?
LM, especially on chronically sun-damaged skin, can exhibit greater subclinical extension, increasing the risk of positive margins when using standard 5 mm excisions.
What do recent large prospective studies suggest about margins for melanoma in situ?
A study of 1120 MIS treated with Mohs micrographic surgery reported that 9 mm margins cleared 98.9% of lesions. 5 mm margins were inadequate in a significant proportion of cases.
How do head and neck MIS differ from trunk or limb MIS regarding margin requirements?
Head and neck lesions often have wider subclinical spread; studies show that 5 mm margins clear only ~65% of cases, and up to 15 mm margins may be needed for ~97% clearance.
What percentage of lesions initially diagnosed as LM can harbor unsuspected invasion?
Various studies report that up to 16–26% of LM may have invasive components identified on final excision, underscoring the importance of thorough margin control.
What is the rationale behind using Mohs micrographic surgery or staged excision for LM?
These techniques provide complete peripheral margin assessment, minimizing the risk of recurrence and sparing healthy tissue—particularly important in cosmetically sensitive areas like the face.
If Mohs or staged excision is not available, how do guidelines generally advise on margin choice for LM?
Larger margins (e.g., ≥1 cm, sometimes up to 1.5 cm or more) are often recommended due to the high rate of subclinical extension in LM. Individualize based on lesion size, location, and clinical judgement.
When are non-surgical treatments like topical imiquimod or radiotherapy considered for LM?
They are generally reserved for patients who cannot undergo surgery or refuse surgery. Ongoing trials (like the RADICAL trial) compare radiotherapy vs. imiquimod for complex LM cases.
Why is early complete clearance of LM crucial in preventing invasive melanoma?
Up to 23% of LM recurrences present with invasive melanoma ≥1 mm in thickness, significantly impacting prognosis.
What is the role of confocal microscopy and dermoscopy in managing LM?
They help in delineating subclinical extensions before surgery, guiding margin selection and reducing the likelihood of positive margins.
