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Diagnostic utility of SOX10 immunostaining in benign lichenoid keratosis: A study of 21 cases
Kaitlyn Levett1, Hanna Siatecka1, A Hafeez Diwan1
1Department of Pathology & Immunology, Baylor College of Medicine, Houston, Texas, USA.
Background:
Benign lichenoid keratosis (BLK) is a cutaneous lesion that can clinically mimic malignancy and may represent regression of a pre-existing lesion. BLK may show epidermal pseudo-nests prompting evaluation for a melanocytic lesion. False positivity of MART-1/Melan-A immunostaining in pseudonests has been showed; however, the value of SRY-related HMG-box 10 (SOX10) staining in BLK with features suspicious for a melanocytic proliferation has not been previously reported.
Methods:
Twenty-one cases of BLK from 2015 to 2020 were identified. Slides were reviewed and SOX10 immunohistochemistry was performed on each case. Subsequently, Melan-A immunohistochemical staining was performed on all cases.
Results:
In 10 cases (47.6%), unexpected SOX10 staining was seen in rare to numerous small, single cells in the epidermis above the basal cell layer. No malignancy was identified. Of the 10 cases, 8 (80%) showed suprabasal SOX10 staining did not show similar suprabasal Melan-A staining; 2 (20%) cases showed scattered suprabasal cells positive for Melan-A.
Conclusion:
SOX10 immunostaining in BLK can highlight scattered cells in the epidermis (not easily noticeable on routine stain). Performing SOX10 immunostain alone on BLK can prompt a misdiagnosis of a melanocytic lesion and should be done with caution.
