Primary malignant melanoma of the rectum: report of two cases

Anorectal Melanoma: An Uncommon Cause of Lower Gastrointestinal Bleeding

Anorectal melanoma (ARM) is a rare, aggressive disease. Given that it presents with local symptoms that resemble other common benign anorectal conditions, ARM is often low on the differential diagnosis. Delayed diagnosis and nonconsensus of treatment options lead to poor prognosis. Here, we report the case of an 85-year-old woman with a history of Irritable bowel syndrome who presented with altered bowel habits and bleeding per rectum. CT revealed a rectal mass with metastatic lesions to the bone, liver, and lungs. Immunohistochemical staining was positive for Human Melanoma Black-45, melanoma antigen recognized by T cells, and SRY-related HMG-box 10. A final diagnosis of ARM was made.

18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in the Evaluation of Anorectal Malignant Melanoma: A Case Series

Melanomas are the malignancies that can affect any anatomic region where melanocytes exist (such as the epidermis, eyes, nasal cavity, and anus). Anorectal melanoma is a rare mucosal melanocytic malignancy, comprising 0.8% of all anorectal malignancies. Here, we report a case series of three patients of anorectal melanoma and role of positron emission tomography/computed tomography in diagnosis and follow-up to evaluate the local recurrence and distant metastases. Of three patients, two presented with rectal bleeding and one with obstruction. One patient had recurrence after 10 months, other after 24 months, and third remained disease free post surgery till 9 months.

Primary Malignant Melanoma of Anorectum CT Findings: a Single Tertiary Center's Experience

Anorectal melanoma is a rare malignancy with very aggressive course. This case series emphasize the role of imaging, contrast-enhanced computed tomography in evaluating such cases before surgery. CT scan of four patients with pathologically proven primary anorectal malignant melanoma was included. CT findings were analyzed from the picture archiving and communication system for the site of involvement, morphological shape, presence of perirectal and anal infiltration, lymphadenopathy, liver metastasis, and occurrence of bowel obstruction for all the four patients. All the four patients presented as polypoidal mass that caused focal expansion and obscuration of rectal lumen without causing colonic obstruction. Perirectal infiltration was seen in 2/4 patients and involvement of anal canal was seen in 3 patients. Distant metastasis was seen in the liver in three out of four patients. In conclusion, primary anorectal malignant melanoma is a rare, highly aggressive tumor and should be considered in patients with a bulky intraluminal polypoid mass that does not cause colonic obstruction in the anorectal region with large-sized lymphadenopathy.

Variable features of 18F-fluorodeoxyglucose positron emission tomography-computed tomography scan in anorectal malignant melanoma: Case reports and review articles

Anorectal malignant melanoma (ARM) is a rare variant of malignant melanoma and even more rare among all anorectal cancers. ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (CT) scan is valuable in staging, restaging, treatment response evaluation, and long-term follow-up of malignant melanoma. Here, reporting two cases of anorectal melanoma with a variety of FDG uptake pattern and CT-based features and reviewed a few articles to evaluate the pattern of FDG uptake.

Primary malignant melanoma of the ascending colon

Malignant gastrointestinal melanoma is usually a metastatic lesion. We report the case of a 67-year-old female patient who presented with intermittent abdominal pain, fever, rigor and diarrhoea. CT scan of the abdomen revealed a large mass at the right iliac fossa with features concerning for intra-abdominal abscess. Exploratory laparotomy confirmed the preoperative diagnosis of abscess, and a right hemicolectomy was performed. Histopathological examination of the surgical specimen was indicative of malignant melanoma, and immunohistochemical examination showed positivity to S100 protein, Melan-A, HMB-45 and vimentin. A series of postoperative clinical, laboratory and imaging examinations revealed no suspicious lesions in the skin, eye, leptomeninges or other sites. Therefore, the diagnosis of primary colonic melanoma was confirmed. Only 36 additional cases of primary colonic melanoma have been reported to date. These rare neoplasms are challenging to diagnose and usually require a multidisciplinary treatment approach, including surgery, chemotherapy and possibly immunotherapy or radiotherapy.

[Gastrointestinal locations of primary melanoma]

Primary gastrointestinal melanomas, part of the mucosal melanoma group, are uncommon. They constitute about five percent of all melanomas and most of them are located in the rectum (3 percent of all melanomas). The prognosis is poor, overall 5-year survival in rectal melanoma is 10-20 percent. We present three of our cases. The first case - a 68-year-old male patient - was operated on for histologically proved rectal melanoma. Three years after radical excision and oncological treatment a metastasis of the primary tumor was diagnosed in the stomach. Total gastrectomy was performed, followed by oncological treatment. In the second case of a 59-year-old male patient an appendectomy was performed for symptoms of appendicitis. The histopathological examination revealed melanoma of the appendix. Further investigations revealed the primary tumor in the stomach and metastases in the lungs as well. The third case - an 82-year-old female patient - was investigated for frequent defecations, mucus in stool and fecal incontinence. Primary melanoma was proved in the lower third of the rectum with multiple hepatic metastases. These three cases in our practice are remarkable for the rarity of the disease, and in two cases the presence of both the primary tumor and the metastasis were located in the gastrointestinal tract.