Mitotic rate and depth of invasion in malignant melanoma

Introduction: Malignant melanoma is initially induced by proliferation of atypical melanocytes in dermal-epidermal junction. When this neoplasm penetrates into the dermis, several variables can affect the extent of spread. Depth of invasion has the most important prognostic value and can be evaluate in several classifications. Mitotic rate of tumor indicates biological action of tumor. This study was designed and performed with the assumption that the penetration depth of tumor is directly affected by mitotic rate. Material and Methods: This cross-sectional descriptive study was done on fifty excisional biopsy of skin lesions with pathologic report as malignant melanoma. Patients characteristics (age, gender and anatomic location) and pathology consequences (tumor subtype, lymphovascular invasive, and tumor thickness) are elicited from patient s pathologic reports. Part of tumor which had more cellular atypia with high mitotic activity selected for determination of mitotic rate in high power filed at microscopic exam by pathologist. Results:In this study, there was a significant statistical relationship between the mean mitotic activity and Clark and Breslow levels and various stages of T. At higher Clark and Breslow levels and higher T stages, the mean mitotic rate increased. Also, there was a positive and significant correlation between Breslow thickness withmitotic rate, as one unit increases in mitosis, 0.8 mm is added to the thickness of the tumor invasion depth. Conclusion: In patients with malignant melanoma, mitotic activity per unit area, along with other histopathological characteristics of the tumor, can indicate depth of tumor invasion. Therefore, in the pathologic report of melanoma which has been removed as incisional, the amount of mitotic activity can be used to estimate the depth of the invasion to plan for excisional biopsy.

Keywords:

Malignant melanoma , Mitotic rate , Depth of the invasion