[489] The Embryonic Stem Cell Transcription Factor SOX2 Is Expressed by Spitz Nevi

JL Baran, AC Laga, LM Duncan, GF Murphy. Massachusetts General Hospital/Harvard Medical School, Boston, MA; Brigham and Women's Hosptial/ Harvard Medical School, Boston, MA

Background: Spitz nevi are benign melanocytic neoplasms that occur predominantly in children and young adults. Lesions with many histopathological features of Spitz nevi may occur in adults, and may display atypical architectural and cytological features. These lesions have been designated “atypical Spitz tumors” recognizing their potential for aggressive behavior. We previously found that the embryonic stem cell transcription factor SOX2 is expressed in a minority of banal nevi (15%) in contrast to malignant melanoma (42%). We sought to determine the expression of Sox2 in Spitz nevi and atypical Spitz tumors.
Design: Fourteen Spitz nevi, 6 atypical Spitz tumors and twenty primary cutaneous melanomas with 10-year follow-up were retrieved from the Pathology Service of the Massachusetts General Hospital. Twenty-one cases of banal nevi were retrieved from the archives of the Department of Pathology at Brigham and Women's Hospital. Five micron paraffin sections were stained with goat anti-human SOX2 immunoperoxidase antibodies (Neuromics, Edina, MN). Immunoreactivity was graded using a semiquantitative scale according to percentage of positive tumor cells as follows: (0 = negative, 1+ ≤ 5%, 2+ =6-25%, 3+ 26-50%, 4+ > 50%).
Results: Three out of 21 (14%) common nevi, 7/ 20 (30%) Spitz lesions (5/14 Spitz nevi and 2/6 atypical Spitz tumors), and 10/20 (50%) malignant melanomas were immunoreactive for SOX2, showing 1+ to 3+ staining. In terms of pattern, the common nevi had uniform diffuse positivity. Spitz showed positivity in random single cells or at the tumor periphery. The melanomas had either positive cells concentrated at the deep/advancing edge (8), in one group of larger cells (1), or randomly (1). No tumors expressed SOX2 in more than 50% of cells (4+). No significant association between SOX2 and presence of atypia in Spitz was found.
Conclusions: We confirm that SOX2 is expressed in a minority (14%) of benign common nevi in comparison to melanomas (50%), and identify SOX2 expression in 30% of Spitz nevi and Spitz tumors.
Category: Dermatopathology

Wednesday, March 24, 2010 1:00 PM

Poster Session VI # 77, Wednesday Afternoon

 

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