[468] Diagnostic Utility and Comparative Immunohistochemical Analysis of MITF and SOX10 in Melanoma In-Situ: A Clinicopathological and Immunohistochemical Study of 50 Cases

J Noelle Buonaccorsi, Saul Suster, Victor G Prieto, Jose A Plaza. Medical College of Wisconsin, Milwaukee, WI; MD Anderson Cancer Center, Houston, TX

Background: The diagnosis of melanoma in-situ may be challenging on purely histological grounds in scant biopsy material. In addition, melanoma in-situ may occasionally be confused with intraepidermal melanocytic hyperplasia in sun damaged skin. Sry-related HMG-BOX gene 10 (SOX10) is a transcription factor involved in regulating the promoter of microphthalamia-associated transcription factor (MITF) which is involved in the development of melanocytes. Both MITF and SOX10 are nuclear immunostains, facilitating diagnosis over cytoplasmic staining in other melanocytic markers such as MART-1. SOX10 has been shown to have superior sensitivity in desmoplastic melanoma when compared to MITF as well as increased specificity, as SOX10 expression was confined to melanocytes while MITF expression was seen in histiocytes and fibroblasts. In addition, SOX10 has been shown to exhibit stronger staining in benign melanocytic proliferations when compared to superficial spreading melanoma and nodular malignant melanoma. The purpose of this study was to compare the immunohistochemical staining characteristics of MITF and SOX10 in cases of melanoma in-situ and actinica keratosis with melanocytic hyperplasia to characterize their immunoprofile and diagnostic utility.
Design: A total of 70 cases were studied, including 50 cases of melanoma in-situ and 20 cases of actinic keratosis. The antibodies employed were MITF and SOX10. Appropriate positive and negative controls were run concurrently for each marker studied.
Results: All cases of melanoma in-situ showed strong nuclear positivity for MITF (50/50). All cases of melanoma in-situ showed positivity for SOX10; however, the proportion of atypical melanocytes showing strong nuclear positivity was variable, and did not approach that seen in MITF. There was no expression of either MITF or SOX10 in adjacent pigmented keratinocytes in the cases of actinic keratosis examined.
Conclusions: In summary, MITF exhibits superior sensitivity over SOX10 in cases of melanoma in-situ. In addition, both MITF and SOX10 can be used to differentiate melanoma in-situ from actinic keratosis with lentiginous hyperplasia. MITF is an effective immunostain for the identification and quantification of melanocytes in the setting of melanoma in-situ, espcially in cases where there is limited tissue and in cases where ther is actinic damage with intraepidermal melanocytic hyperplasia.
Category: Dermatopathology

Wednesday, March 21, 2012 1:00 PM

Poster Session VI # 113, Wednesday Afternoon


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