|Year : 2013 | Volume
| Issue : 3 | Page : 232-233
Anorectal melanocarcinoma: A case report and review of literature
Kshetrimayum Raju Singh, Kh Amitkumar Singh, TY Babu Singh, N Sanjib Singh
Department of Surgery, Regional Institute of Medical Sciences, Imphal, Manipur, India
|Date of Web Publication||19-Feb-2014|
Kshetrimayum Raju Singh
Department of Surgery, Regional Institute of Medical Sciences, Imphal, Manipur
Source of Support: None, Conflict of Interest: None
Primary anorectal malignant melanoma is very rare disorder accounting for 1% of all anorectal malignancies other than adenocarcinoma. It presents usually like polypoid lesion which projects into the anorectal lumen and progresses rapidly towards the rectal wall. We report a case in a 40 years old woman presented with a polypoidal mass and bleeding per rectum. The tumour is usually at advance stage at the time of diagnosis. Because of their relative scarcity, only few clinical trials have evaluated the treatment options. Aggressive surgical treatment is usually not recommended for a clinically localized disease. The disease should be considered as one of the differential diagnosis in anorectal malignancies other than adenocarcinoma. Early diagnosis with histological features confirmed with immunohistochemistry will help in appropriate treatment and long term survival of the patient.
Keywords: Anorectal, Immunohistochemistry, Malignant melanocarcinoma
|How to cite this article:|
Singh KR, Singh K, Babu Singh T Y, Singh N S. Anorectal melanocarcinoma: A case report and review of literature. J Med Soc 2013;27:232-3
| Introduction|| |
Primary malignant melanoma of anus and rectum is rare and highly lethal neplasm constituting less than 1% of all melanomas and 4% of anorectal tumors other than adenocarcinoma. Owing to its rarity and histologic variability, misdiagnosis as carcinoma, sarcoma and lymphoma is common. Sometimes this can be mistaken for benign conditions like haemorrhoids or rectal polyp as they present with rectal bleeding. There are no definite recommendations for the management of these lesions. Treatment strategies have varied from the radical abdominoperineal resection to the conservative wide local excision. we report a case of anorectal melanocarcinoma in a 40 year old woman presented with history of bleeding and mass per rectum.
| Case Report|| |
A 40-year-old female patient presented with the history of bleeding and mass per rectum for the last 3 months and 1 month respectively. She noticed the bleeding per rectum during the last trimester of her latest pregnancy and a polypoidal mass was found prolapsed during the delivery. She was discharged after the delivery and readmitted in the surgery department for her prolapsed mass per rectum. On examination, patient was found marked pale and digital rectal examination revealed a polypoidal, pedunculated and lobulated firm mass of 9 cm × 8.5 cm size, at 7 O' clock position about 2.5 cm away from the anal verge [Figure 1]. Chest X-ray and ultrasonography of whole abdomen was found normal. Emergency polypectomy was performed under spinal anesthesia. Gross histopathology revealed a flessy tissue mass measuring 9 cm × 8.5 cm × 8 cm, grey brown with areas of congestion and hemorrhage. Microscopically, multiple sections studied showed only tumor tissue composed of cells arranged in loosely scattered singles, diffuse sheets and in vague pseudo-alveolar pattern. Individual tumor cells were large, had a moderate amount of cytoplasm and round to oval vesicular nuclei with prominent eosinophilic nucleoli. Majority of the cells contained abundant intracytoplasmic melanin pigment. Abnormal mitoses were seen and areas of hemorrhage were noted. Features were of melanocarcinoma [Figure 2].
|Figure 1 : The gross picture of the anorectal polypoidal lesion before surgery|
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| Discussion|| |
Primary anorectal malignant melanoma is very rare disorder accounting for 1% of all anorectal malignancies other than adenocarcinoma.  It usually affects women in the fifth or sixth decade and presents with bleeding per rectum and constipation. It also presents usually like polypoid lesion, which projects into the anorectal lumen and progresses rapidly towards the rectal wall. In our case, patient was 40 years old presented with bleeding and mass per rectum. Patients presenting with rectal bleeding and sensation of a mass are usually attributed to hemorrhoids or polyp. The epithelial lining of the anal canal is glandular in the upper part and squamous in the lower part. The middle zone also known as anal transitional zone is characterized by an epithelium, which bears resemblance to that of anal glands, but show little mucous secretion.  The absence of early clinical manifestations and the lack of clinical suspicion contribute for delayed diagnosis. Immunohistochemical studies such as vimentin, keratin, S-100 and human melanoma black (HMB-45) are usually positive. In our case, we did not send blood for immunohistochemistry. Upto 60% have metastasis at the time of diagnosis.  In our case, the disease was limited to rectum and anal canal without evidence of metastasis. Patients with true mucosal melanoma - including melanoma of mucosa of the respiratory tract, vagina and anal canal generally have a poor prognosis. Because of their relative scarcity, few clinical trials have evaluated treatment options. It is usually not recommended an aggressive surgical approach to patients with clinically localized disease. In particular, it is generally recommended local excision of anal melanomas rather than abdominoperineal resection. In our case, patient was treated with local excision. Abdominoperineal resection is associated with greater morbidity, leaves the patient with a permanent colostomy, offers no survival advantage and does not treat at - risk inguinal nodes unless the procedure is combined with groin dissection.  However, some literatures mention abdominoperineal resection is the treatment of choice for patients with <2 mm wide lesion.  Abdominoperineal resection appears to have some effect in controlling symptoms caused by local and regional disease, but has minimal impact on prognosis.  Adjuvant radiation therapy may be administered to patients with mucosal melanoma in an attempt to decrease the risk of locoregional recurrence.  The factors for poor prognosis include advanced disease at the time of diagnosis and rich vascularity, which increases the risk of hematogenous metastasis. 
| Conclusion|| |
Anorectal malignant melanoma is rare and should be considered as one of the differential diagnosis in anorectal malignancies other than adenocarcinoma. Efforts should be made for the detection of this disease in early stage. Early diagnosis with histological features confirmed with immunohistochemistry will help in appropriate management and long-term survival of patient.
| References|| |
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[Figure 1], [Figure 2]