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 Table of Contents  
Year : 2021  |  Volume : 1  |  Issue : 2  |  Page : 116-118

Anorectal malignant melanoma – Case series

Department of General Surgery, Dr. Mehta Hospital, Global Campus, Chennai, Tamil Nadu, India

Date of Submission23-May-2021
Date of Decision14-Jun-2021
Date of Acceptance15-Jun-2021
Date of Web Publication22-Dec-2021

Correspondence Address:
Dr. Jayabal Pandiaraja
Dr. Mehta Hospital, Global Campus, No. 50, Poonamallee High Road, Velappanchavadi, Thiruverkadu, Chennai - 600 077, Tamil Nadu
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/aort.aort_13_21

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Anorectal melanoma is a rare tumor of the anal canal. It is <1% of all anorectal malignancies and 1%–2% of melanoma. Because of the presentation and aggressive nature of the tumor, the prognosis remains poor. The patient often presents with nonspecific complaints such as bleeding per rectum or altered bowel habits. Because of the late presentation and aggressiveness, the selection of treatment modality is limited. This case series reviews the clinical features and management of patients with anorectal malignant melanoma.

Keywords: Abdominal perineal resection, anorectal melanoma, lymphadenectomy, wide local excision

How to cite this article:
Pandiaraja J. Anorectal malignant melanoma – Case series. Ann Oncol Res Ther 2021;1:116-8

How to cite this URL:
Pandiaraja J. Anorectal malignant melanoma – Case series. Ann Oncol Res Ther [serial online] 2021 [cited 2022 Aug 8];1:116-8. Available from: http://www.aort.com/text.asp?2021/1/2/116/333301

  Introduction Top

The malignant melanoma anal canal is a rare tumor of the anal canal. Only few patients present in the early stage. However, most patients present in an advanced stage as locoregional or metastatic disease. Because of the presentation and aggressive nature of the tumor, the prognosis for a patient with an anorectal malignant melanoma remains poor. The patient often presents with nonspecific complaints such as bleeding per rectum (most commonly) and/or altered bowel habits. Because of the late presentation and aggressive clinical presentation, the selection of treatment modality is limited.

  Case Series Top

This case series evaluates the four cases of anorectal malignant melanoma. Data from all four patients treated for anorectal malignant melanoma from 2012 to 2014 were reviewed. Gender, age, type of symptoms, duration of symptoms, distance from the anal verge, tumor size, per rectal examination, pathological examination, depth of invasion, nodal involvement, immunohistochemistry, surgical modality, postoperative chemoradiotherapy, local recurrence, and distance metastasis were analyzed.

Most of the anorectal malignant melanoma was seen in women as compared to the men. The age of patients with anorectal melanoma ranged from 35 years to 67 years. The most common presentation of anorectal melanoma was hematochezia. The duration of symptoms range from 3 months to 6 months, but in most cases, presentation was within 3 months. Most of the anorectal melanoma originated from the anal canal. Typical black mass was presented in 75% of the cases [Figure 1] and [Figure 2]. The remaining cases presented as amelanotic melanoma. Misdiagnosis was common in anorectal melanoma. One case was misdiagnosed with hemorrhoids. In 75% of cases presented with metastasis during initial presentation [Table 1].
Figure 1: Ultrasound image shows malignant lymph node compression femoral vessels

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Figure 2: Computed tomography image of huge malignant melanoma with involvement of adjacent structures

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Table 1: Case profile of anorectal melanoma

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  Discussion Top

Malignant melanoma of the anal canal is an unusual tumor of the anal canal, comprising <1% of all anorectal malignancies and 1%–2% of melanoma.[1] It is the most common melanoma following cutaneous and ocular melanoma. Most commonly affect women with men: women ratio 0.75.[2] Most commonly located on the anal canal or at the anal verge (65%) and the remaining 35% located on the distal rectum.[3] Etiology of anorectal melanoma remains controversial. Cutaneous and ocular melanomas mostly occur in sun-exposed areas due to exposure to ultraviolet radiation, but anorectal melanoma occurs in nonsun exposed areas. Hence, ultraviolet radiation may not be a risk factor. However, some studies show the relationship between retroviral infection and human papillomavirus association with anorectal melanoma.[4]

The most common presentation was bleeding per rectum or anal discomfort, altered bowel habit, and anorectal mass. The diagnosis is often delayed due to misdiagnosed as thrombosed pile mass or anal polyp and fistula. Per rectal examination provides information regarding size, shape, consistency, ulceration, and fixity. Pigmentation may or may not be there, because amelanotic melanoma can also arise from the anorectal region.[5] Because of the late presentation, the majority of anorectal melanoma presented in an advanced stage, with presenting lesions more than 2 mm in thickness.[6] The most common site of nodal metastasis is the inguinal lymph nodes, mesenteric lymph nodes, hypogastric lymph nodes, and para-aortic lymph nodes. Numerous prognostic factors are there for cutaneous malignant melanoma, but for anorectal melanoma, most important prognostic factors are perineural invasion, tumor necrosis, nodal status, and amelanotic melanoma by histology.[7]

Most of the time, the diagnosis is made by digital rectal examination with biopsy. Additional investigations are required, such as endoscopy, ultrasound, contrast computed tomography abdomen to identify nodal and visceral metastasis and stage of the disease. Because of the late presentation and lack of control trial, no specific treatment strategy has been created for anorectal melanoma. Surgery was the main modality of treatment; either by wide local excision or abdominoperineal resection with a colostomy. Most of the studies showed no significant difference in either procedure through recurrence, survival benefit, and distance metastasis without lymphadenectomy. However, abdominoperineal resection creates more morbidity to the patient compared to only wide local excision.[8]

Surgical management of lymph nodes (lymphadenectomy) is controversial. The morbidity and mortality that follows regional lymph nodes resection are very high. Some studies support regional lymphadenectomy for the palpable lymph node. The role of prophylactic lymphadenectomy for nonpalpable lymph nodes is not warranted, because it does not improve survival. The role of sentile lymph node biopsy is yet to be evaluated.[9]

Another modality of treatment for anorectal melanoma is chemotherapy, immunotherapy, and radiotherapy. The most common chemotherapeutic agent was dacarbazine. Immunotherapy such as interferon-alpha and interleukin-2 has also been tried.[10] Malignant melanoma is relatively chemoresistant but radiation can be used for unresectable tumors, locally recurrent, metastatic disease, spinal cord collapse, central nervous system dysfunction due to brain metastasis.

  Conclusion Top

Anorectal melanoma mostly presents at the late stage, even with the early presentation; the prognosis will be poor due to early regional and distant metastasis. Because of the female preponderance, patients who underwent perineal examination should also undergo per rectal examination to identify the early lesion. In the absence of strong survival benefit of abdominoperineal resection in managing the nonmetastatic form of the disease, it is reasonable to consider wide local excision as the initial treatment of choice.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Kothonidis K, Maassarani F, Couvreur Y, Vanhoute B, De Keuleneer R. Primary anorectal melanoma-A rare entity: Case report. J Surg Case Rep 2017;2017:rjx060.  Back to cited text no. 1
Ranjith S, Muralee M, Sajeed A, Arun PM, Cherian K, Nair CK, et al. Anorectal melanoma: Experience from a tertiary cancer care center in South India. Ann R Coll Surg Engl 2018;100:185-9.  Back to cited text no. 2
Malaguarnera G, Madeddu R, Catania VE, Bertino G, Morelli L, Perrotta RE, et al. Anorectal mucosal melanoma. Oncotarget 2018;9:8785-800.  Back to cited text no. 3
Serra M, Santos T, Martins M, Sardo L. Amelanocytic anorectal malignant melanoma-Case report. Int J Surg Case Rep 2019;55:164-7.  Back to cited text no. 4
Carcoforo P, Raiji MT, Palini GM, Pedriali M, Maestroni U, Soliani G, et al. Primary anorectal melanoma: An update. J Cancer 2012;3:449-53.  Back to cited text no. 5
Meguerditchian AN, Meterissian SH, Dunn KB. Anorectal melanoma: Diagnosis and treatment. Dis Colon Rectum 2011;54:638-44.  Back to cited text no. 6
Singer M, Mutch MG. Anal melanoma. Clin Colon Rectal Surg 2006;19:78-87.  Back to cited text no. 7
Yeh JJ, Shia J, Hwu WJ, Busam KJ, Paty PB, Guillem JG, et al. The role of abdominoperineal resection as surgical therapy for anorectal melanoma. Ann Surg 2006;244:1012-7.  Back to cited text no. 8
Stefanou A, Nalamati SP. Anorectal melanoma. Clin Colon Rectal Surg 2011;24:171-6.  Back to cited text no. 9
Yeh JJ, Weiser MR, Shia J, Hwu WJ. Response of stage IV anal mucosal melanoma to chemotherapy. Lancet Oncol 2005;6:438-9.  Back to cited text no. 10


  [Figure 1], [Figure 2]

  [Table 1]


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