[506] Utility of SOX10 as a Reliable Marker for Melanocytes in Sun-Damaged Skin.

Kunle Ojemakinde, Patrick Adegboyega. LSU Health Sciences Center, Shreveport, LA

Background: In sun-damaged skin, it is sometime problematic distinguishing between atrophic actinic keratosis and atypical melanocytic proliferations on routine Hematoxylin and Eosin stain, especially when there is pseudomelanocytic proliferation. Attempts to resolve this diagnostic challenge with Melan A Immunohistochemistry has been reported to result in spurious staining results and diagnostic errors with dire consequences. This study examines the usefulness of a relatively new melanocytic marker (SOX10) in such cases.
Design: 23 consecutive cases of atrophic actinic keratosis with features of lentigo maligna-like features were stained with antibodies against HMB45 (a well established cytoplasmic melanocytic marker) and SOX 10 (a new marker located in the nucleus). Immunohistochemistry was performed using modified avidin-biotin detection method with antigen retrieval. For each antigen, the immunostained slides were evaluated for location of positive staining reaction – being it in melanocytes and/or in keratinocytes.
Results: In all 23 cases, melanocytes in the basal layer of the epidermis stained positive with both HMB45 and SOX 10 in the cytoplasm and nuclei respectively. Although the number and distribution of cells stained by both antibodies were comparable, the nuclear staining reaction of SOX10 is more readily discerned and more easily interpreted compared with HMB45's cytoplasmic staining reaction and associated non specific granular staining reactions noted in keratinocytes. No positive staining for SOX10 was detected in the dysplastic keratinocytes (Actinic Keratosis cells) in any of the 23 cases.

Conclusions: Immunohistochemical stain for SOX10 (a nuclear stain) is a reliable marker for distinguishing between melanocytes and keratinocytes in sun damaged skin; and does not produce the false positive (cytoplasmic) staining reaction reported with Melan A in such situations.
Category: Dermatopathology

Tuesday, March 1, 2011 9:30 AM

Poster Session III # 119, Tuesday Morning


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