[489] Use of Immunohistochemistry (HMB-45,p16 and Ki-67) in the Diagnosis of Spitzoid Lesions

Ozlem Erdem, Doina Ivan, Victor G Prieto. Gazi University Medical School, Ankara, Turkey; University of Texas MD Anderson Cancer Centre, Houston, TX

Background: Spitzoid neoplasms, which include spitz nevus (SN), atypical spitz nevus (ASN) and spitzoid melanoma (SM), are diagnostically challenging lesions. The histological similarities between SN and other spitzoid lesions may result in considerable problems in differential diagnosis. The aim of this study was to compare immunohistochemical expression of a group of markers including gp 100 (HMB-45), P16 and Ki-67 in spitzoid neoplasms.
Design: Thirty cases of spitz nevi, 19 cases of atypical spitz nevi and 20 cases of spitzoid melanoma were retrospectively selected from the archives of the Department of Pathology at the University of Texas, MD Anderson Cancer Center from the period 1992-2006. The diagnoses were confirmed by two authors including also review of clinical charts for possible events. Immunohistochemistry was performed in each case for gp100 (with HMB45), P16 and Ki-67. HMB-45 was evaluated in melanocytes of 3 different localizations of the lesions (i.e. junctional component, and superficial and deep dermis). Cytoplasmic P 16 intensity and percentage were separately evaluated in the dermis. Proliferative index was calculated by counting the cells that expressed Ki-67 per/mm².
Results: Ki-67 proliferative index was significantly higher in SM compared to SN and ASN (p<0.0001). Intensity of cytoplasmic P16 staining was stronger in SN and ASN compared to SM; however the difference between groups were not significantly different. p16 expression percentages was significantly higher in SN and ASN compared to SM (p<0.001). The percentage of intraepidermal cells labeled with HMB-45 was not different among groups. However, more cells in superficial and deep dermis were labeled with HMB-45 in SM compared to ASN and SN (p<0.0001).
Conclusions: According to our data, spitzoid melanoma shows higher expression of gp100 (with HMB45) and Ki67, and lower of p16 than Spitz nevi and atypical spitzoid lesions. Therefore, immunohistochemical analysis of these markers may help in the diagnosis of spitzoid lesions.
Category: Dermatopathology

Wednesday, March 21, 2012 1:00 PM

Poster Session VI # 122, Wednesday Afternoon


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