A retrospective histological study of 669 cases of primary cutaneous malignant melanoma in clinical stage I. 4. The relation of cross-sectional profile, level of invasion, ulceration and vascular invasion to tumour type and prognosis.

A selected series of 669 primary cutaneous malignant melanomas, stage I, was studied. The series includes 86 lentigo maligna melanomas, 259 superficial spreading malignant melanomas, 194 nodular malignant melanomas and 130 unclassifiable malignant melanomas. The cross-sectional profile, level of invasion, ulceration and vascular invasion were graded. The relation of these features to each other and to tumour type was studied by X2 tests. The prognostic value was also studied. The most common finding was a slightly elevated surface, level III of invasion, no ulceration and no vascular invasion. Most of these tumours were superficial spreading malignant melanomas. A good prognosis was associated with a flat cross-sectional profile, level II of invasion, no ulceration and no vascular invasion. A poor prognosis was associated with marked protrusion of the surface, level IV--V of invasion, ulceration and vascular invasion. Lentigo maligna melanomas tended to be more benign while nodular malignant melanomas tended to be more malignant than the average. A superficial spreading malignant melanoma could vary in either direction. The prognostic value of level of invasion and ulceration was found to be greater than that of tumour type. The prognostic importance of invasion no further than level III is stressed. Level of invasion ought to be reported to the clinician as well as the tumour type.