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A comparative immunohistochemical study of MART-1 expression in Spitz nevi, ordinary melanocytic nevi, and malignant
R Bergman1, H Azzam, E Sprecher
1Department of Dermatology, Rambam Medical Center, Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel.
Background:
The histopathologic differential diagnosis of Spitz nevus (SN) from malignant melanoma (MM) may be difficult.
Objective:
We attempted to elucidate the pattern of expression of a newly recognized melanocyte-specific melanosomal protein MART-1 in routinely processed specimens of SNs, MMs, and ordinary melanocytic nevi (MNs) and to see whether it can help to differentiate between them.
Methods:
Twenty SN, 22 MM, and 27 ordinary MN were immunostained with anti-MART-1 monoclonal antibody (clone A103).
Results:
All SNs, MNs, and MMs demonstrated cytoplasmic staining for MART-1 in some of their tumor cells, of which 17 of 20 (85%) and 24 of 27 (89%) of SN and MN, respectively, demonstrated positive stainings in more than half of their tumor cells, as compared with only 10 of 22 (45%) of the MM (P <.05). The majority of lesions in all 3 types of tumors showed a homogeneous mode of staining, although MM tended to show a more heterogeneous pattern. A consistent pattern of stratification of staining with progressive descent into the dermis was not demonstrated in these tumors.
Conclusion:
MART-1 does not differentiate between SN, MM, and ordinary MN in a consistent pattern, but it may be used as a marker for these tumors.