Spontaneous regression of metastatic melanoma.

Spontaneous regression of malignant melanoma is a well-known but rare event. It seems to be caused by immunological enhancement similar to the regression observed after intralesional injection of Bacille Calmette-Guérin into cutaneous melanoma metastases. A patient is presented in whom an incisional biopsy of a metastatic melanoma in an inguinal lymph node was followed by complete disappearance of the metastasis. Reviewing the literature, several similar patients were found in whom spontaneous regression of a metastatic melanoma occurred after an incomplete excision or biopsy of the tumor. It appears that in rare instances, an unspecific mechanical stimulus may trigger an increase in immunocompetence, although laboratory evidence for this has only rarely been produced. A plea is made for serial immunological studies in consecutive patients with melanoma, to further elucidate these puzzling phenomena.