Primary jejunal melanoma as a cause of adult intussusception: a case report and review of literature

Primary melanoma of the small bowel is a rare clinical entity with a paucity of published reports in literature. Most cases of gastrointestinal melanomas are metastatic lesions arising from skin or ocular origins. This is a case report of a 63 year old female with adult intussusception with jejunal melanoma as the lead point. The index patient had a long history of abdominal pain associated with significant weight loss and presented with features of intestinal obstruction. The possibility of a regressed or unidentified extra-intestinal site cannot be absolutely excluded as the patient did not have a PET scan. Due to the vague nature of clinical symptoms and signs, the diagnosis of small bowel melanoma is difficult, especially in patients with no obvious cutaneous pathology. A high index of suspicion for melanoma as a malignant lead point for adult intussusception should always be entertained.


Introduction
Melanoma is a malignant tumor originating from melanocytes which are usually located in the skin, the eye's choroid, the meninges, and the anal margin. They account for 1-3% of all intestinal tumours [1].
Primary melanoma of the small bowel is a rare clinical entity with a paucity of published reports in literature. Most cases of gastrointestinal melanomas are metastatic lesions arising from skin or ocular origins. The small bowel is frequently affected and is responsible for about 62% of malignant causes of small bowel intussusception [2]. The diagnosis of a primary gastrointestinal melanoma is clinically difficult because it is a diagnosis of exclusion where other common sources of metastasis must first be ruled out and most small bowel melanoma present with non-specific features such as abdominal pain, unexplained weight loss, gastrointestinal bleeding with features of anemia. Rare acute presentation may include intussusception and bowel perforation [3]. Clinically, adult intussusception remains an elusive diagnosis and accounts for only 1%-5% of intestinal obstructions in adults, with a pathologic lead point seen in up to 90% of cases [4]. There are several investigative modalities used in the diagnosis of uncomplicated small bowel melanoma which may include abdominal Computed Tomography (CT) and barium studies although they have low sensitivities. Video capsule endoscopy (VCE) is the gold standard as these lesions are usually beyond the reach of most conventional endoscopes. Surgery is the mainstay for intestinal melanomas and an oncologic resection should be done in resectable tumours [5]. Regardless of whether the melanoma is primary or secondary, intestinal melanomas are highly aggressive tumours, the prognosis is worse than cutaneous and other non-gastrointestinal melanoma. The survival rate at 5years is less than 10% [6]. This is a case report of a 63 year old female with adult intussusception with jejunal melanoma as the lead point. This is the first (to the best of our knowledge) reported case of adult intussusception caused by jejunal melanoma in Africa.

Discussion
Malignant melanomas are relatively common cancers making up around 2% of all tumors [7]. The vast majority of melanomas are cutaneous but non-cutaneous tumors occur albeit very rarely [7].
Malignant melanoma is also the commonest cancer to specifically metastasize to small bowel, comprising 50-70% of small bowel secondary cancers. The jejunum and ileum are most commonly involved. There is a report of melanomas in several body parts reported in Nigeria but this is the first report of a primary melanoma originating from the jejunum [8]. proximal and distal to the lesion, and should include resection of the associated affected mesentery and lymph nodes [1]. Manual reduction of the intussusception which is the gold standard treatment of pediatric intussusception is rarely a method of treatment in adults [4].
More often than not, the exact diagnosis may not be known and many workers advocate that resection of the intussuscepted segment be done without reduction in a bid to prevent spillage and also dissemination of tumour [4]. En-bloc resection reduces the possibility of recurrence and avoids repair/anastomosis on oedematous, ischemic bowel. A formal oncologic resection in patients above 60years with intussusception is recommended due to the possible high incidence of a malignant lead point which may approach 80% [4].

Conclusion
In conclusion, primary SBM is a rare entity, which can be clinically difficult to diagnose in the setting of possible primaries at other places.

Competing interests
The authors declare no competing interests.