Melanoma with ulceration, light micrograph. Ulceration in a melanoma refers to the absence of intact epidermis overlying the major portion of the tumour. It is generally a sign of a rapidly growing tumour with a high risk of metastasis and poor prognosis. Loss of epidermis due to trauma or artifactual distortion must be ruled out. The presence/absence of ulcer and the width of ulcer are independent prognostic factors. In an ulcerated melanoma, the Breslow thickness is measured from the base of the ulcer to the deepest point of invasion.