True about melanoma of the anal canal is -
The anal canal is the third most common site for melanoma, following skin and eye.
It's a rare tumor comprising less than 1% of anorectal malignancies.
It is radioresistant and prognosis is very poor.

Clinical presentation

average age is 50 to 60 yrs.
nonspecific symptoms are seen → bleeding, pain or anal mass.
usually misdiagnosed as thrombosed hemorrhoids.

Treatment

Melanoma is resistant to chemotherapy & radiotherapy
Surgery offers the only cure but by the time the symptoms appear, the level of invasion precludes surgical cure in most patients. In these patients, the disease has metastasized or is deeply invasive.
A few patients present with isolated local or locoregional disease that is potentially resectable for cure.
The two surgical procedures used are

Wide local excision and APR

Recurrence is common and usually occurs systemically regardless of the initial surgical procedure. Local resection does not increase the risk of local or regional recurrence and APR offers no survival advantage over local excision. Because of the morbidity associated with APR, wide local excision is recommended for initial t/t of localized melanoma. APR may be required if the tumor involves a significant portion of the anal sphincter or is circumferential.
Present usually as anal bleeding
AP resection gives better result than local excision
Local recurrence at the same site after resection
Radiosensitive