Malignant anal melanoma is a rare disorder, corresponding to 0.05-1.0% of all anorectal tumors, and 0.4-1.6% of all other melanomas7,8,9. Its rarity can be confirmed by the fact that for every anal melanoma, there are eight squamous cell carcinomas and 250 anal adenocarcinomas8,9.
The article´s aim is to present a case of a malignant anal melanoma coexisting with colon adenocarcinoma, in addition to a discussion on how to speed up the diagnosis with simple routine measures, and report an objective treatment.
A 57-year-old patient was admitted with weakness, pale skin and a lump in the inguinal region. According to his medical history, one year prior to admittance the patient was treated for anemia. At the time, he presented positive fecal occult blood test. Endoscopy and contrast exams were normal and no weight loss or changes in bowel movements were noticed.
In the six months prior to admittance, the patient felt sporadic pain in the anal canal that ceased with the use of NSAID suppositories. After 30 days, he sought medical attendance and underwent proctosigmoidoscopy and colonoscopy, along with biopsy of lesions in the anal canal and cecum. The patient was then diagnosed with poorly differentiated carcinoma of the canal and well differentiated tubular adenocarcinoma of the cecum. At the time, a lump began forming in the root of the thigh, just below the inguinal fold.
The patient was refered to Sírio-Libanês Hospital in São Paulo, Brazil, for surgical treatment of the colon lesion and clinical treatment of the anal canal lesion (Figure 1), as he refused to operate the anal lesion. Abdominal ultrasonography and thorax tomography did not reveal any findings. Surgery was then performed with right ileocecal colectomy, intra-operatory biopsy of lesion in the anal canal and of the right inguinal lymph node.
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