Published online Dec 26, 2021. doi: 10.12998/wjcc.v9.i36.11369
Peer-review started: May 26, 2021
First decision: June 15, 2021
Revised: June 15, 2021
Accepted: July 2, 2021
Article in press: July 2, 2021
Published online: December 26, 2021
Processing time: 211 Days and 4.3 Hours
Anorectal melanoma is a tumour that is difficult to identify due to its rarity and variability of presentation. Insufficient data published in the literature do not allow for diagnostic and treatment guidelines to be established. Anorectal melanoma has the worst prognosis among mucosal melanomas and is frequently misdiagnosed by standard identification methods.
A 66-year-old woman presented with intermittent anal bleeding, pain, and tenesmus in the past month, with no associated weight loss. Colonoscopy revealed a cauliflower-like tumour with a diameter of 1.5 cm, with exulcerated areas and an adherent clot but without obstruction. Biopsy results identified an inflammatory rectal polyp with nonspecific chronic rectitis. Tumour markers CA 19-9 and CEA were within the normal range. After 6 mo, due to the persistence of symptoms, a pelvic magnetic resonance imaging scan was performed. A lesion measuring 2.8 cm × 2.7 cm × 2.1 cm was identified at the anorectal junction, along with two adjacent lymphadenopathies. No distant metastases were detected. Immunohistochemistry was performed on the second set of biopsies, and a diagnosis of anorectal melanoma was established. Surgical treatment by abdominoperineal resection was performed. Evolution was marked by the appearance of lung metastases at 1 mo postoperatively, detected on a positron emission tomography-computer tomography scan, and perineal recurrence after 5 mo. After molecular testing, the patient was included in an immunotherapy trial.
This case highlights the difficulty of establishing a definitive early diagnosis of anorectal melanoma, the importance of performing histological analysis on a well-represented biopsy specimen, and the poor prognosis, even with radical surgery.
Core Tip: Anorectal melanoma is a rare type of melanoma with the worst prognosis among mucous melanomas. The location and nonspecific symptoms of anorectal melanoma make it difficult to detect. Even histological examination can be misleading in the absence of obvious pigmentation and suspicion raised by the clinician to induce immunohistochemical examination. In this context, the diagnosis is late, in advanced stages, and the rarity of cases has not allowed the development of treatment guidelines.