Anatomical Pathology

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Browsing Anatomical Pathology by browse.metadata.advisor "du Plessis, Pieter"

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    Treatment of lentigo maligna of the head and neck with staged excision in South Africa : assessing surgical excision margins with Melan A, SOX10 and PRAME immunohistochemistry
    (Stellenbosch : Stellenbosch University, 2022-11) de Wet, Johann; Schneider, Johann Wilhelm; du Plessis, Pieter; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Pathology: Anatomical Pathology.
    ENGLISH SUMMARY: Lentigo Maligna (LM) is a subtype of melanoma in situ that occurs on sun-damaged skin, typically on the head and neck area of older individuals. LM is associated with significant subclinical extension beyond the visible clinical margins and therefore recommended surgical excision margins may be inadequate for complete surgical clearance of the tumour. Staged Excision (SE) has emerged as the treatment of choice for LM of the head and neck. It allows for complete margin control, superior clearance, and lower recurrence rates compared to conventional wide local excision (WLE). Differentiating between actinic melanocyte hyperplasia (AMH) and LM at the peripheral margin complicates the assessment of completeness of excision when using this technique. Objectives: The study aimed to describe the patient demographics, tumour characteristics, and histological findings of LM cases on the head and neck treated with SE. Secondary objectives included: (1) To determine if standard recommended surgical excision margins for LM of the head and neck are adequate to achieve a 97% clearance rate and if any patient or tumour characteristics warranted wider margins, (2) To determine whether immunohistochemical (IHC) staining with SOX10 and PRAME aids in diagnosing LM on excision margins compared to conventional Hematoxylin and Eosin (H&E) and Melan A IHC staining. Methodology: The study involved a retrospective chart review of all patients diagnosed with LM of the head and neck and treated with SE at the Skinmatters Mohs Micrographic Surgery and Reconstructive Unit. Tissue sections of LM cases with LM reported to be present at margins were immunohistochemically stained with SOX10 and PRAME and reviewed by a Mohs surgeon and a pathologist with expertise in melanoma pathology. Results: The first component of the study showed that 6mm, 9mm, and 12mm surgical excision margins obtained complete excision in 60.94%, 71.88%, and 90.64% of the LM cases, respectively. A surgical excision margin of 18mm correlated with complete excision in 96.7% of tumors, while complete excision in 100% of LM cases required a 21mm margin. Recurrent tumors (p-value = 0.01) and tumour size larger than 20mm were associated with wider surgical excision margins (pvalue= 0.154). The second study component evaluated IHC stains and consisted of 35 sections. Based on H&E and Melan A IHC staining, 23 sections were diagnosed as LM by the initial pathologist. Further staining with SOX10 IHC showed only 8 cases consistent with a diagnosis of LM and 9 revealing actinic melanocyte hyperplasia (AMH). PRAME was positive in 5 of the 8 cases of LM and negative in all 9 cases of AMH (p=0.009). The presence of melanocyte nests (p=0.29) and pagetoid spread (p = 0.003) were the most reliable histological findings for distinguishing LM from its mimics. Conclusion: This study of LM in a South African population corroborates that the standard surgical excision margins recommended by international melanoma guidelines for LM are inadequate to achieve a 97% clearance rate. Recurrent LM cases and tumours larger than 20mm may require wider margins. The study further concluded that SOX10 is a more specific and sensitive marker for melanocytes when assessing for LM on excision margins compared to Melan A. The addition of PRAME can be useful to confirm or exclude the diagnosis in challenging cases.