Anorectal melanoma: not a haemorrhoid.

AIM: Melanoma of the anorectum is a rare malignancy which is particularly aggressive compared to cutaneous melanoma. Due to its presenting symptoms, location and rarity there is often a delay in diagnosis. The purpose of this paper is to raise awareness of anorectal melanoma in New Zealand by presenting our institution's experience of four cases.

METHODS

The presentation, management and outcomes of four cases are described. A review of the literature surrounding anorectal melanoma was also carried out.

RESULTS

The four cases (3 male, 1 female, aged 30-87 years) all presented with haemorrhoidal symptoms of anal discomfort and/or outlet rectal bleeding. Three patients had metastatic disease at presentation, and the remaining patient was found to have a concurrent lymphoma which was treated with chemotherapy before he underwent excision of the melanoma. Surgical excision is the mainstay of treatment and recent literature suggests transanal excision of the primary tumour to have equivalent overall survival to abdominoperineal resection.

CONCLUSION

Anorectal melanoma is rare tumour with a poor prognosis. Patients are commonly misdiagnosed as having haemorrhoids; therefore a high index of suspicion is needed to enable early diagnosis. Metastatic disease is common at presentation, and the key prognostic indicator. Local control can be obtained with transanal excision, avoiding the morbidity of abdominoperineal resection. Adjuvant therapies available at present provide little survival advantage.