Anal Nodular Melanoma Masquerading as Thrombosed Haemorrhoid: A Case Report

Anorectal Melanoma (AM) is an aggressive and rare malignancy with a poor prognosis. It is more commonly observed in women over the age of 50 years. Due to its rarity, AM is often undetected at the time of diagnosis or has already metastasised. This case describes a 67-year-old male who presented with a mass descending per annum for two years. This was associated with pain and blood in the stools for two weeks. History of constipation present. No known comorbidities and no past surgical history. The mass was lobular and soft in consistency. It was suspected to be thrombosed haemorrhoids, and he was taken up for surgery. The mass was excised in toto, and on histopathological examination, it was diagnosed to be invasive melanoma- Nodular melanoma of the anal canal with no evidence of lymph vascular emboli in the section. Immunohistochemistry (IHC) markers showed pan-Cytokeratin (CK)-negative, S-100-positive, HMB-45-positive and MELAN A-positive. No signs of recurrence were noted for six months, and the patient is currently on follow-up. Anal melanomas are often mistaken for a thrombosed pile mass, and improper surgery might result in recurrence. Careful planning and evaluation before proceeding with excision is advised.