Immunohistochemical Double Staining of Ki-67/Melan-A in Melanocytic Nevi and Malignant Melanomas / 대한피부과학회지

ABSTRACT

BACKGROUND: Melanomas need to be differentiated from benign melanocytic lesions during diagnosis. However, it is difficult to differentiate them using histopathology alone, since both neoplasms have broad morphological spectrums and subtle differentiating features. OBJECTIVE: To evaluate the usefulness of Ki-67/Melan-A double staining for differentiating melanoma from benign melanocytic nevi. METHODS: We selected 20 cases of intradermal nevi, 20 cases of compound nevi, 5 cases of dysplastic nevi, and 25 cases of melanoma from clinicopathologically proven cases reviewed by the Department of Dermatology at our medical center. Ki-67/Melan-A double staining was performed, and the Melan-A verified Ki-67 index (Ki-67-M index) and Ki-67 index were measured. The immunopositivity was measured in the deepest third of the lesions. RESULTS: The Ki-67-M index of intradermal nevi, compound nevi, dysplastic nevi, and melanoma were 0.4+/-0.9%, 1.0+/-1.1%, 4.3+/-1.7%, and 24.1+/-10.9%, respectively. The best Ki-67/Melan-A cut-off point to distinguish melanomas from benign melanocytic nevi was 5%; the sensitivity and specificity were 100% and 97.7%, respectively. Immunopositivity in the deepest third of the intradermal nevi, compound nevi, and melanoma, were 10.5%, 20%, and 100%, respectively; the sensitivity and specificity for diagnosing melanoma were 100% and 84.6%, respectively. The sensitivity and specificity of combined Ki-67-M and immunopositivity in the deepest third for diagnosing melanoma were 100% and 97.7%, respectively. CONCLUSION: The Ki-67-M index and immunopositivity in the deepest third of melanoma were significantly higher than that of benign melanocytic nevi. Therefore, Ki-67/Melan-A double staining is a potentially valuable diagnostic tool for differentiating melanoma from benign melanocytic nevi.