Teaching Case

An 81-year-old male with a history of treated melanoma in 2018 presented with recurrent abdominal pain and vomiting for 3 months. The pain was located in his central abdomen with each episode lasting up to 15 minutes. Esophagogastroduodenoscopy performed 3 weeks prior to admission was unremarkable.

Imaging performed during prior hospital admissions was consistent with a history of intermittent self-resolving small bowel obstruction (SBO). Plain film radiography performed three months prior to the current admission demonstrated a single dilated small loop of bowel in the mid-abdomen, which suggested enteritis or developing bowel obstruction (figure 1). A small bowel series performed one month later demonstrated multiple dilated proximal small bowel loops with air-fluid levels and non-distended distal small bowel loops, suggestive of a partial SBO (figure 2). Computed tomography (CT) of the abdomen and pelvis without contrast performed during the current admission demonstrated long segment small bowel intussusception (figures 3a-3b). Follow-up CT of the abdomen and pelvis with IV contrast a few days later revealed SBO secondary to enteroenteric intussusception in the lower abdomen with worsening dilatation of the upstream small bowel (figures 4a-4c). Additionally, there was an enhancing lesion near the distal margin of the intussuscepted loop of bowel measuring 4.9 cm, concerning for a small bowel mass acting as a lead point for the patient’s intussusception.

BACKGROUND

Intussusception is defined as a proximal portion of the intestine invaginating a distal portion of intestine. More than 50% of cases occur in children less than 1 year of age with males twice as likely to be affected; only 5% of all cases are found in adults [1].

Causes of intussusception are divided into three categories: benign, malignant and idiopathic. Malignancy is implicated in 30% of cases of intussusception in the small bowel and 66% of cases in the large bowel [2]. One specific type of malignancy central to the current case is melanoma, a rare and aggressive form of skin cancer which can quickly metastasize to lymph nodes and other body systems, including the gastrointestinal tract. Small bowel metastasis has been found in up to 60% of malignant melanoma patients in post-mortem studies, however clinical detection rates are typically suggested to be around 1-5% [3]. SBO from intussusception is the most common complication when metastasis occurs in the small bowel [4].

CLINICAL PERSPECTIVE

Intussusception is difficult to diagnose due to variable clinical presentation and imaging features. The symptoms of intussusception are non-specific, and can include abdominal pain, vomiting, diarrhea, nausea, melena, and an abdominal mass [5]. The triad of cramping, bloody diarrhea, and a palpable mass is typically seen in pediatric populations [2,5].

IMAGING PERSPECTIVE

Plain film imaging is initially performed due to the non-specific presentation of intussusception; this will typically show signs of intestinal obstruction. An active intussusception visualized on small bowel follow-through may demonstrate a stacked coin or coil-spring appearance [2]. Ultrasound imaging can be useful in demonstrating key signs of intussusception, such as the doughnut/target sign, but can be non-diagnostic due to artifact and operator-dependency [2]. Therefore, the most sensitive method for diagnosing intussusception is an abdominal CT with IV and oral contrast, where it will appear as concentric bowel rings. Additionally, this will provide further information about whether there is a lead point, the lesion’s location, and whether there is invasion into surrounding structures.

When melanoma metastasizes to the small bowel, imaging findings are diverse, and may appear similar to other conditions such as primary gastrointestinal malignancy, lymphoma, or infective processes. Melanoma typically appears as polypoid nodules on cross-sectional imaging [6]. Additionally, metastatic lesions within the gallbladder, soft tissues, and peritoneum may also be detected which should increase clinical suspicion for malignant melanoma metastasis, especially in patients with a current or prior history of melanoma [3,6].

OUTCOME

Surgical intervention is almost always required when intussusception secondary to malignancy is suspected, with CT imaging used to plan for targeted surgery [2]. When the lead point is a metastatic lesion, such as in this case, resection and pathological sampling would be required in order to definitively diagnose neoplasm [7]. The diagnosis of melanoma is done through histologic studies showing the presence of melanocytes, which can be supported by staining with HMB-45 and S-100 [4]. For the treatment of metastatic melanoma, surgical resection is performed in patients who have a small number of completely resectable lesions. Advanced metastatic melanoma will require systemic therapies in addition to resecting symptomatic metastasis [8]. Prognosis when melanoma metastasizes to the gastrointestinal tract is poor, with a life expectancy of four to six months [4].

The patient in the current case report had a known history of left shoulder melanoma, for which he underwent complete left axillary lymph node dissection four years earlier in 2018. While other cases in literature have identified metastatic melanoma as a lead point of intussusception [9], the currently presented case report is unique as the patient had recurrent self-resolving episodes for 3 months. The possibility of metastatic melanoma to the bowel was never considered until the patient underwent exploratory laparotomy with small bowel resection where a 5.5 cm mass, later proven pathologically to be metastatic melanoma, was resected with negative margins.

TAKE HOME MESSAGE

Metastatic melanoma can spread to the bowel and cause intussusception, most commonly affecting the small bowel. This differential should be considered when a patient has a history of melanoma and presents with recurrent episodes of intussusception.

Written informed patient consent for publication has been obtained.