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HMB-45 recognizes stimulated melanocytes
B R Smoller1, N S McNutt, A Hsu
1Department of Pathology, New York Hospital, Cornell Medical Center 10021.
Abstract:
A monoclonal antibody (HMB-45) was previously reported to bind to melanoma cells, and the junctional component of nevus cells, but not to normal adult melanocytes. We have tested HMB-45 binding in several conditions under which melanocyte stimulation might be expected in adults, i.e. 3 simple lentigines, 2 solar lentigines, 7 recent surgical scars (from re-excision of non-melanocytic tumors), 2 surgical scars from re-excisions of melanomas (after complete primary excisions), 9 hemangiomas from non-sun-exposed skin, 1 basal cell carcinoma, 1 acute ecchymosis, 1 keloid, and 1 dermatofibroma. Positive controls included 6 malignant melanomas and 1 fetal skin sample. Melanocytes were strongly positively stained overlying hemangiomas, within or near recent surgical scars of melanocytic and non-melanocytic tumor re-excisions, near basal cell carcinoma, and in fetal skin. Melanocytes either were not stained or were stained only focally for trace amounts in the normal skin near the new margins of the wide re-excision specimens for melanoma, i.e., at a distance from the scar, in the simple lentigines and in the fibrotic lesions. Thus, HMB-45 is staining an antigen which appears in adult melanocytes during stimulation and in fetal skin, as well as in melanomas. This stimulation is associated with conditions that would have increased vascularity, suggesting a melanocyte response to a plasma factor, or other endothelial cell derived factor. HMB-45 would not be a useful marker for residual melanoma cells in melanoma re-excision specimens.
Insights
The HMB-45 antibody stains stimulated adult melanocytes and fetal skin cells, not just melanoma. This suggests HMB-45 marks a melanocyte response to factors associated with increased vascularity, limiting its use for detecting residual melanoma.
Area of Science:
- Dermatopathology
- Immunohistochemistry
- Melanocyte Biology
Background:
- The HMB-45 monoclonal antibody is known to bind melanoma and nevus cells, but not normal adult melanocytes.
- Understanding HMB-45 binding in stimulated adult melanocytes is crucial for accurate melanoma diagnosis and monitoring.
Purpose of the Study:
- To investigate HMB-45 antibody binding patterns in various conditions involving adult melanocyte stimulation.
- To determine if HMB-45 can reliably identify residual melanoma cells in post-excision specimens.
Main Methods:
- Immunohistochemical staining using the HMB-45 antibody on tissue samples from simple lentigines, solar lentigines, surgical scars, hemangiomas, basal cell carcinoma, ecchymosis, keloid, dermatofibroma, malignant melanomas, and fetal skin.
- Comparison of HMB-45 staining in stimulated versus non-stimulated adult melanocytes and in melanoma versus normal skin.
Main Results:
- HMB-45 strongly stained melanocytes overlying hemangiomas, near surgical scars, near basal cell carcinoma, and in fetal skin.
- Melanocytes in simple lentigines, fibrotic lesions, and normal skin distant from melanoma excision margins showed minimal or no HMB-45 staining.
- HMB-45 identified an antigen present in stimulated adult melanocytes and fetal skin, in addition to melanomas.
Conclusions:
- HMB-45 marks an antigen expressed by adult melanocytes during stimulation, potentially in response to vascular or endothelial factors.
- The observed HMB-45 staining patterns indicate it is not a reliable marker for detecting residual melanoma cells in re-excision specimens.