A Study on Expression of Ki-67 Antigen in Melanocytic Skin Lesions

Choi, Tae Jin; Roh, Doe Kywn; Lee, Dong Won; Kim, Si Yong; Cho, Baik Kee; Kang, Chang Suk

Abstract

BACKGROUND: Evaluation of the cell proliferation activity of neoplasm is useful in making a diagnosis and prognosis. Immunohistochemical staining using MIB1 monoclonal antibodies has recently been demonstrated to assess tumor cell proliferation activity easily, because it can be performed on paraffin-embedded specimens and is available in a retrospective study.
OBJECTIVE
The purpose of this study to investigate (a) the use of Ki-67 antibodies in distinguising between benign melanocytic nevus and malignant melanoma, and (b) the correlation between the Ki-67 labelling index(positive number per 100cells) and histological parameters such as the Breslow index, Clarks level, mitotic rate(mitoses per 100cells) in malignant melanoma. METHOD: A total of 37 formalin-fixed, paraffin-embedded melanocytic skin lesions(benign melanocytic nevus 21; malignant melanoma 16) were stained with MIB1 using the one hour method. The values of the Ki-67 labelling index were measured in all the lesions. For each case of malignant melanoma, the Breslow index, Clarks level and mitotic rate were quantitatively evaluated. RESULT: The Ki-67 labelling index averaged 2.6 +1.4 in benign melanocytic nevus and 22.4+ 6.2 in malignant melanoma. In malignant melanoma, the values of the Ki-67 labelling index were significantly correlated with Breslow index(r=0.764), Clark's level(r=0.885) and mitotic rate(r=0.754).
CONCLUSION
Our findings suggest that Ki-67 may be a useful tool in distinguising between benign melanocytic nevus and malignant melanoma. According as Ki-67 labelling index correlates with well-established prognostic parameters(Breslow index, Clark's level, mitotic rate), it may therefore carry additional prognostic value for patients with malignant melanoma.