it represents less than 1% of all melanomas and accounts for less than 4% of anal malignancies.1 arm is documented as the third most common location of melanoma , after cutaneous and ocular .
patients with arm often present with local symptoms such as rectal bleeding ( 55% ) , rectal masses ( 34% ) , and anal pain ( 13%).2 arm has been shown to result in worse prognoses than cutaneous melanoma , with a median survival of 24 months and a 5-year survival rate of 10%.3 in the rectum , melanocytes are located at the anal transitional and squamous zones .
most arms arise from the dentate line , and 65% are located within the anal canal or at the anal verge.4 arm spreads along submucosal planes , and is often too widespread for complete resection at the time of diagnosis and almost all patients die because of metastases.5 although there are various treatment strategies for arm , surgical treatment remains the main therapeutic modality due to its relative rarity , with abdominoperineal resection ( apr ) and wide local excision ( wle ) being performed in most cases .
the role of adjuvant chemotherapy and immunotherapy in the treatment of arm is yet to be established .
several studies have reported cases of long - term survival with treatment consisting of only local surgical excision,6,7 and there have been other cases removed by endoscopic mucosal resection ( emr ) alone in japan.8 here , we present a case of arm treated with emr with adjuvant interferon therapy .
a 77-year - old man was admitted to our emergency department with anal bleeding . he had a 4-month history of anal bleeding and recent aggravation .
his medical history included cerebral infarction with right sided weakness and hypertension . on admission , he was hemodynamically stable and his hemoglobin level was 11.4 g / dl .
urgent colonoscopy demonstrated a dark - colored , polypoid mass with a diameter of 1.5 cm and oozing hemorrhage adjacent to the anal verge .
analysis of the resected specimen , measuring 1.51.2 cm in size , revealed a black - pigmented solid tumor with a short stalk ( fig .
microscopic findings revealed diffuse infiltration of round or spindle - shaped tumor cells , and the contained melanin and tumor cells were immunohistochemically positive for human melanin black-45 ( hmb-45 ) ( fig .
after polypectomy , the resection margin contained positive tumor cells and it was difficult to confirm the depth of tumor invasion because of the presence of a short stalk .
neither lymphatic nor vascular invasion were noted . to evaluate systemic metastases , a fluorine-18-fluorodeoxyglucose ( fdg )
the pet / ct scan demonstrated increased fdg uptake in the distal rectum ( fig .
though this finding might have indicated a remnant lesion of arm , there was also the possibility of false positivity associated with initial polypectomy .
however , the pet / ct scan showed no positive regional lymph nodes or systemic metastases ( fig .
we recommended surgical treatment , such as apr or wle , to the patient and his family because of the poor prognosis of malignant melanoma and the positive resection margin .
however , they refused surgery due to the patient 's old age and general weakness secondary to cerebral infarction . therefore , we designed and performed additional emr for the positive resection margin ( fig .
tumor cells were not observed in the resected specimen . since there was a positive resection margin after the first polypectomy , and difficulty in evaluating the depth of tumor invasion , we decided on and recommended adjuvant therapy .
the patient was treated with interferon 2b injection , 2010 iu / m , five times per week for four weeks , then 1010 iu / m , three times per week for 24 weeks subcutaneously . during the 5-year follow - up period , the patient was asymptomatic and abdominal ct scans and sigmoidoscopic examinations at 3 - 6-month intervals revealed no evidence of recurrence ( fig . 3c and 4b ) .
melanoma of the anorectal region is a relatively rare neoplasm with a poor prognosis . the overall 5-year survival rates in patients with arm range from 4 - 31% even if radical surgery and chemotherapy are performed , while median survival varies from 16 - 28 months.3,9,10 treatment strategies have varied , from the radical apr to the conservative wle , but the main controversy has been whether apr is needed or wle is adequate for complete treatment .
apr , although associated with a high rate of morbidity , has long been thought to be the best means of management for arm . in 1997 , however , there was a paradigm shift after two major studies found minimal improvements in survival .
retrospective studies were performed , which looked at 135 patients with anal melanoma.2,11 patients in both studies had uniformly poor survival rates and the apr group had a longer survival rate , but this was not statistically significant.11 in a study from thibault et al.,2 37 patients had curative resection but no significant survival difference was found between wle and apr when comparing disease stage and 5-year survival.12 before 1997 , 70% of all patients underwent apr , and after 1997 , 80% would undergo wle.13 furthermore , because the completion of lymphadenectomy in apr may not affect survival,13 wle with or without adjuvant therapy seems to offer good locoregional control without reducing the survival rate , and may be a therapeutic modality for patients with small , superficial arms.14 apr should be offered for patients with locally advanced disease or as a salvage therapy following recurrence.14,15 there is no current adjuvant therapy dictated as the standard of care in arm , particularly in cases involving metastatic disease .
however , it is clear that chemotherapy alone without surgery provides no benefit.12 radiation therapy has not been shown to provide any benefit , except occasionally for palliative care in cases of unresectable tumors.16 some patients with metastatic melanomas have been shown to respond to therapy with interferon  and interleukin-2 , suggesting that metastatic melanoma is susceptible to immune assault.16 emr is not a " wide " but a " local excision " method . in japan , emr for malignant melanoma in the gastrointestinal tract has been performed in only five cases , and there are no reported cases from other countries.8 relatively long - term survival was achieved in all cases ( > 6 years ) . among these cases , however , two were melanomas in the esophagus , another two required additional surgical treatment and chemotherapy , and the other involving a 85-year - old male with a 2218 mm - sized tumor and submucosal invasion , needed repeated emrs because local recurrence had occurred four times previously.8 in cases of arm in which a shallow depth of the invasion and a small tumor size , long - term survival is expected even if less invasive surgery such as emr is performed.8 for the assessment of invasion depth in arm , the preferred modality is mri .
anatomical and functional diagnostic imaging , such as ct , mri , and pet / ct scans are available to assess lymph node involvement and to exclude or confirm the presence of distant metastases , as well as loco - regional recurrences.17 until now , however , pet / ct scans have been reported rarely in cases of arm for the detection of distant metastasis or recurrent disease.17 in the present case , emr with adjuvant interferon therapy lead to 5-year disease free survival . even though emr in this case was not the ideal treatment modality and it the depth of tumor invasion was unclear , there was no local recurrence , distant metastases , or additional intervention needed after the first treatment for 5 years .
worse histological prognoses have been found to be associated with tumor thickness , tumor necrosis , and perineural invasion.2,11 in our case , there was no necrosis and perineural invasion , and though it was difficult to assess the depth of invasion exactly , we suspected superficial invasion confined to the submucosal layer because emr removes only mucosa and superficial portions of the submucosa .
the resection margin of the tumor in the first polypectomy was positive , but negative in the second emr .
however , because the resection margin was positive and the depth of tumor invasion was not clear in the initial polypectomy , we needed adjuvant interferon therapy after polypectomy and emr . in conclusion , arm has a poor prognosis and needs surgical treatment .
nevertheless , if there is a shallow depth of invasion and the general condition of the patient is not good enough to justify surgery , less invasive surgical methods such as emr with or without adjuvant therapy may be performed .
 anorectal melanoma is a rare neoplasm that accounts for less than 1 - 4% of anorectal malignant tumors . 
 the main therapeutic modality for anorectal melanoma is surgical treatment , with abdominoperineal resection or wide local excision being the most common approaches . a 77-year - old male with a history of cerebral infarction and hypertension presented with anal bleeding . here 
 , we report a case of anorectal melanoma treated by endoscopic mucosal resection with adjuvant interferon therapy rather than surgical resection . 
 the patient has been disease - free for 5 years after endoscopic treatment . 