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Melan A and S100 protein immunohistochemistry in feline melanomas: 48 cases
J A Ramos-Vara1, M A Miller, G C Johnson
1Veterinary Medical Diagnostic Laboratory, College of Veterinary Medicine, University of Missouri, Columbia 65205, USA. ramosj@missouri.edu
Insights
Melan A and S100 protein immunohistochemistry aids feline melanoma diagnosis. Melan A is more specific, while S100 protein is more sensitive for identifying these canine tumors.
Area of Science:
- Veterinary Pathology
- Oncology
- Immunohistochemistry
Background:
- Feline melanoma diagnosis can be challenging, particularly for amelanotic or less differentiated tumors.
- Accurate differentiation is crucial for appropriate treatment and prognosis in veterinary oncology.
Purpose of the Study:
- To evaluate the utility of Melan A and S100 protein immunohistochemistry in diagnosing feline melanoma.
- To compare the sensitivity and specificity of Melan A and S100 protein in feline melanoma specimens.
Main Methods:
- Immunohistochemistry was performed on 48 formalin-fixed, paraffin-embedded feline melanoma specimens.
- Monoclonal antibody to Melan A and polyclonal antibody to S100 protein were utilized.
- Tumor types included cutaneous, oral, mucocutaneous, and metastatic melanomas.
Main Results:
- S100 protein was detected in 87.5% (42/48) of tumors, while Melan A was positive in 67% (32/48).
- Melan A showed higher specificity, with only one non-melanocytic tumor (sebaceous adenoma) showing reactivity.
- 75% of amelanotic melanomas were negative for Melan A, highlighting its utility in differentiating from pigmented basal cell tumors.
Conclusions:
- Melan A is a specific marker for feline melanoma, useful for differentiating it from other skin tumors.
- S100 protein is a sensitive marker but less specific than Melan A.
- Combined use or careful interpretation of both markers can improve diagnostic accuracy in feline melanoma.
Abstract:
Immunohistochemistry, using a monoclonal antibody to Melan A and a polyclonal antibody to S100 protein, was applied to 48 formalin-fixed, paraffin-embedded specimens of feline melanoma. Forty-two cutaneous, three oral, one mucocutaneous, and two metastatic melanomas comprised the tumors. Thirty-two tumors (67%) were positive for Melan A and 42 (87.5%) were positive for S100. All but one of the tumors that were positive for Melan A were also positive for S100. S100 was detected in 11 of 16 tumors that were negative for Melan A. Seventy-five percent (9 of 12) of amelanotic melanomas were negative for Melan A. Normal adrenal cortex, the cerebellum, and the skin had cells that were positive for Melan A. Sebaceous adenoma was the only nonmelanocytic tumor examined that reacted with antibody to Melan A. Although less sensitive than S100 protein, Melan A is more specific for melanoma and is useful in differentiating feline cutaneous melanoma from the more common pigmented basal cell tumor.
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