From the Guidelines
To confirm lentigo maligna, the most important immunostains are Sox10, S100, Melan-A/MART1, HMB45, and tyrosinase, as they are sensitive and specific for melanocytic differentiation. These immunostains are crucial in identifying atypical melanocytes along the dermal-epidermal junction and adnexal structures, particularly in cases where morphologic indicators are lacking 1.
- Key immunostains for lentigo maligna include:
- Sox10: a sensitive but less specific marker for melanocytic lesions
- S100: a sensitive but less specific marker for melanocytic lesions
- Melan-A/MART1: a more specific marker for melanocytic differentiation
- HMB45: a more specific marker for melanocytic differentiation
- Tyrosinase: a more specific marker for melanocytic differentiation
- These immunostains help distinguish lentigo maligna from mimics such as solar lentigo, pigmented actinic keratosis, and benign melanocytic hyperplasia, particularly in sun-damaged skin where melanocyte assessment can be difficult on routine histology alone 1.
- It is essential to interpret immunostaining results alongside H&E histology, as architectural features remain crucial for diagnosis 1.
- Additional stains, such as Ki-67 and p16, may be helpful in assessing proliferation rates and loss of expression in melanoma, but are not the primary immunostains for confirming lentigo maligna 1.
From the Research
Immunostains for Confirming Lentigo Maligna
To confirm lentigo maligna, several immunostains can be used, including:
- PRAME (Preferentially Expressed Antigen in Melanoma) 2
- MART-1/Melan-A 3, 4
- HMB-45 3, 5
- MiTF (Microphthalmia Transcription Factor) 5
- Mel-5 3, 5
- S-100 3
Characteristics of Each Immunostain
- PRAME: sensitive (93.5%) and specific (94.7%) method for diagnosing LM on biopsy and excision 2
- MART-1/Melan-A: useful for visualizing atypical melanocytes on frozen sections during Mohs micrographic surgery 4
- HMB-45: can be used to differentiate melanocytes from surrounding keratinocytes 5
- MiTF: allows for greater distinction of melanocytes from keratinocytes with melanized cytoplasm, making it a superior marker for quantification of melanocytes 5
- Mel-5: can be used to estimate the density of melanocytes within dermatoheliotic skin 5
- S-100: can be used as a diagnostic tool for lentigo maligna, although its specificity and sensitivity are not well established in the provided studies 3