Halo naevus or malignant melanoma: A case report.

This is a report describing the case of a 66-year-old male with development of halo naevi. A biopsy of one of these naevi revealed a malignant melanoma with extensive regression. The purpose of this report is to identify that development of halo naevi outside of childhood or adolescence should raise suspicion and may require biopsy.

A 66-year-old male presented to the combined Dermatology and Plastic Surgery clinic with an 18-month history of halo naevi on his trunk, arms and legs. Due to the occurrence of halo naevi at the age of 66, three biopsies were performed, which demonstrated regression. One biopsy however, of a lesion on the lower back had demonstrated a malignant melanoma of Breslow thickness 0.6 mm, no mitoses and extensive regression.

A wide local excision of the lesion was performed which demonstrated no evidence of invasive malignancy. Staging CT scan did not demonstrate any metastatic disease. There was some dehiscence of the wound, which was subsequently allowed to heal by secondary intention.

Within three months, the wound had healed well, but new halo naevi had arisen. A further lesion was excised which demonstrated a halo naevus. Within six months, the halo naevi had begun to disappear.

A halo naevus can also be known as a Sutton's naevus or a leukoderma acquisitum centrifugum and are generally considered to be benign. They more commonly develop in adolescents and children. They consist of a depigmented halo surrounding a benign melanocytic naevus. This can develop within weeks and regress usually within two years.

There is a recognised association between melanoma and hypopigmentation, the mechanism for which is not understood. It is proposed that this can be due to an immune response against antigens present in both melanoma and normal melanocytes, which can result in vitiligo. Therefore, the development of vitiligo suggests a better prognosis, as the patient is developing immunity to the melanoma. The occurrence of malignant melanoma presenting as a halo naevus has also been described by Fishman (1976) and Mandalia et al. (2002).

In conclusion, this case demonstrates that halo naevi arising in an older adult should be considered for biopsy. (Figure 1)

Figure 1

Lesion with halo, biopsy-proven as a malignant melanoma.