[Post-traumatic acral melanoma: an underestimated reality?]

The role of trauma in the physiopathology of malignant melanoma remains controversial. We report a case of acral melanoma in which a characterized trauma seems implicated in tumour progression; we performed a review of the literature.

A 73-year-old male consulted for a lesion of his right big toe. Physical examination revealed a dystrophic and hyperkeratotic nail destroyed by a growing lesion. Histological study showed an ulcerated superficial spreading melanoma with a Breslow thickness of 4mm. He had previously had this same toe broken, leaving gradually worsening dystrophy of the nail; the toe was injured again spontaneously and by partial removal of the nail tablet.

A number of cases of "post-traumatic" melanomas have been reported. This hypothesis, though widely admitted for other tumours, remains debated for melanomas mainly because of possible recall bias. In this patient, there was a clear continuum of the lesion as well as topographic correspondence between the initial trauma, the remaining dystrophy and the appearance of the melanoma. Case-control studies have identified trauma as an independent risk factor for acral melanoma with a high relative risk; such risk is multiplied for repeated trauma, suggesting a "dose-effect" relationship. Trauma could act as the promotional stage of melanoma mediated by cytokines released during wound healing or it could cause direct activation of micro-vascular tumour cell transport.

Our observation and literature research provide convincing arguments for a role of trauma in the development of acral melanomas. Dermatologists must pay attention to any unusual changes in an old scar.