Spontaneous regression of melanoma.

Primary cutaneous melanoma has a tendency to disappear spontaneously. Histologically the active phase is characterized by a dense infiltrate of lymphocytes similar to that seen in spontaneously disappearing naevi. The regression process may continue until the tumour has been completely destroyed, or it may cease when only a part of the tumour has been destroyed. The lymphocytes disappear when the process halts leaving vascular scar tissue with a variable number of pigment-containing phagocytes. As a result of this a certain number of distinctive clinical patterns can be recognized: (1) An inflammatory nodule with or without pigmentation; (2) scarring in the tumour; (3) several foci of melanoma simulating multicentricity; (4) pigmented lesion with a depigmented halo; (5) pigmented scar with surviving melanoma cells; (6) pigmented scar without surviving tumour cells; and (7) metastatic melanoma with no demonstrable cutaneous primary. Only melanomas with a component of superficial spreading type have been found undergoing spontaneous regression.