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"Histiocytic markers" in melanoma.
N L Pernick1, M DaSilva, M D Gangi
1The Barbara Ann Karmanos Cancer Institute and Wayne State University School of Medicine, Detroit, Michigan, USA.
Summary
Malignant melanomas can mimic histiocytes, and common histiocytic markers like alpha-1-antitrypsin (AAT) and CD68 are often positive in melanomas. These markers may not reliably distinguish melanomas from true histiocytic lesions.
Area of Science:
- Oncology
- Pathology
- Immunohistochemistry
Background:
- Malignant melanoma, known as the "great imitator," can present with cellular morphologies resembling histiocytes.
- Immunohistochemical stains are crucial for differentiating histiocytic lesions from melanomas, but cross-reactivity of histiocyte markers in melanoma has been reported.
Purpose of the Study:
- To evaluate the immunoreactivity of common histiocytic markers in melanomas.
- To assess the utility of histiocytic markers in distinguishing melanomas from histiocytic tumors.
Main Methods:
- Examined 43 primary and metastatic melanomas using traditional melanoma markers (S100, HMB45, NKI-C3) and histiocyte markers (alpha-1-antitrypsin [AAT], CD68, HAM56, Mac387, Muramidase).
- Semi-quantitatively recorded the extent and intensity of staining for each marker.
Main Results:
- Melanoma cells showed high reactivity for S100 (100%), HMB45 (91%), NKI-C3 (91%), AAT (95%), and CD68 (86%).
- Reactivity for HAM56 (26%), Mac387 (7%), and Muramidase (30%) was less frequent and often focal.
- AAT and CD68 staining was typically diffuse but weaker compared to traditional melanoma markers.
Conclusions:
- Melanomas frequently exhibit immunoreactivity for histiocytic markers, particularly AAT and CD68.
- The frequent positivity and variable staining patterns of histiocytic markers can complicate their use in differentiating melanomas from histiocytic lesions.
- Histiocytic markers may not be consistently reliable for distinguishing melanomas from histiocytic tumors.