Pathological grading of malignant melanoma of skin cancer

Malignant melanoma is a highly malignant skin cancer. Its pathological manifestations include a large number of dispersed or nested melanoma cells in the epidermis and dermis, which extend horizontally or vertically and deep into the dermis and subcutaneous tissues. It can be divided into the following grades according to pathological manifestations:

1. Classification by invasion depth

Melanoma is divided into five grades according to the depth of invasion, and the higher the grade, the worse the prognosis. Grade I: Tumor cells are confined to the epidermis above the basement membrane; Grade II: Tumor cells break through the basement membrane and invade the papillary dermis; Grade III: Tumor cells fill the papillary dermis and invade further downward, but not to the reticular dermis; Grade IV: Tumor cells have invaded the reticular dermis; Grade V: Tumor cells have passed through the reticular dermis and invaded the subcutaneous fat layer.

2. Vertical thickness grading

Melanoma is divided into 5 grades according to the thickness of the thickest part of the melanoma (the thickness from the granular layer to the deepest part of the melanoma) measured by the eyepiece micrometer. The thicker the melanoma, the worse the prognosis. Grade I: thickness ≤ 0.75MM; Grade II: thickness between 0.76 and 1.50MM; Grade III: thickness between 1.51 and 3.00MM; Grade IV: thickness between 3.01 and 4.50MM; Grade V: thickness > 4.50MM. This microscopic grading method was later widely used and proved to be of great value in judging prognosis.