An unusual case of a patient with two concurrent small bowel perforations from metastatic melanoma

Malignant melanoma commonly metastasizes to the bowel and remains as the most common metastatic tumor in terms of tumors in the bowel which are mostly asymptomatic [1]. However, in rare cases the tumor can cause bowel perforation and often with a poor prognosis. We present a rare case of two concurrent small bowel perforations due to melanoma deposits.

The patient was a 62-year-old woman who was known to have metastatic malignant melanoma to the inguinal lymph nodes and brain, presented to the Emergency Department with an acute abdomen. She had been on regular dexamethasone for cerebral edema from the metastasis as well as on Binimetinib and Encorafenib as a targeted therapy, as systemic therapies had not been successful. The disease started 12 years ago, and her primary cutaneous site was documented to be in her right back, which was treated with wide local excision.

She had experienced an abrupt onset of right-sided abdominal pain overnight and had multiple episodes of vomiting, prompting her to present to the Emergency Department then. Her observations showed that she was tachycardic but remained normotensive and apyrexic. She had generalized peritonitis on abdominal examination.

Her biochemical markers revealed a raised C-reactive protein (CRP) level of 333 mg/L and a white cell count (WCC) of 6×109/L. She had a computed tomography (CT) abdomen pelvis subsequently which showed pneumoperitoneum with no obvious sites but mural thickening of the mid descending colon was noted suspicious for a perforation (Figure 1).

The decision was made for an urgent laparotomy. During the surgery, it was found that she had 4 quadrant feculent peritonitis with small bowel contents. While running through the small bowel, multiple tumor deposits were noted with 2 perforations. The proximal perforation was 140 cm from the terminal ileum and the distal one 90 cm from the ileocaecal valve. Sixty centimeters of small bowel were resected, incorporating both perforations (Figure 2). Remaining deposits were left behind and small bowel was anastomosed side-to-side using staples. Following the peritoneal lavage, a drain was placed and the abdomen was primarily closed.

Histopathology confirmed ileum which had been resected showing three deposits of metastatic melanoma with regional lymph nodes (5/5). The tumor deposits involved the full thickness of the bowel wall with overlying mucosal ulceration. Features of perforation were present in two out of three deposits. Metastatic melanoma was identified in regional lymph nodes also (5/5) and the resected margins were otherwise negative.

Her progression was slow following the surgery and on day 12 post-surgery, she had developed a left lower limb deep vein thrombosis for which she was started on oral anticoagulation. She was subsequently discharged on day 14 without further complications from the surgery. She survived for another six months after the operation and passed away from her progression of her metastatic melanoma with brain metastases.

Melanoma represents approximately 5% of all the skin cancers and is well known for its ability to metastasize to a wide range of atypical locations. Malignant melanoma remains as the most common cancer to metastasize in the gastrointestinal tract. It is found in the small intestine at 58% of the time, colon 22% as well as the stomach at 20% [2]. Prognosis in this type of disease is poor with a median survival rate of approximately eight months when discovered [3].

According to Berger et al., when melanoma invades into the small bowel, there is a high incidence of it having multiple localized lesions. It has been found to have an incidence of nearly 90% at the time of metastatic melanoma having multiple sites [4].

Patients with metastatic intestinal melanoma tend to be asymptomatic and only 1–4% of the metastases to the gastrointestinal tract are detected prior to death. In such cases, the diagnosis is often only made after developing a complication [5]. The clinical presentation of small bowel melanoma deposits includes abdominal pain, iron-deficiency anemia, altered bowel habits, and weight loss. Other rarer presentations would be deposits causing perforations, obstruction, intussusception, or fistulas [6],[7].

Metastases in the gastrointestinal tract are also difficult to be picked up with imaging, such as the CT performed for this patient did not detect the presence of metastases, with the CT scan showing only around 65% sensitivity as a mode of detection [6]. In regard to imaging, a full body positron emission tomography (PET) scan with fluorodeoxyglucose is much better when compared to a normal CT in terms of both sensitivity and specificity with researchers strongly believing that it should be the primary imaging modality for disease recurrence investigation [8]. In terms of diagnosing gastrointestinal involvement by metastatic melanoma, endoscopic options such as enteroscopy and video capsule endoscopy can be considered [9]. However in the setting of emergency, CT scan would be the most useful choice.

As mentioned, there are limited literatures with bowel perforation secondary to metastatic melanoma [7]. One similar case is that of Klausner et al., in which a 49-year-old patient survived for six months following bowel resection, similar to the patient in the case report [2]. Another similar case is that of Alwhouhayb et al., in which a 79-year-old female patient presented with generalized peritonitis. During emergency laparotomy, a perforated tumor was found in the jejunum, with histology confirming presence of melanoma but sadly the patient passed away shortly after surgery [1]. As per Rosalia et al., due to the nature of this rarity, there are fewer than 6 reported cases of metastatic melanoma causing perforations and fewer than 20 small bowel intussusceptions documented [5].

To date, there do not seem to be any case reports of patients presenting with 2 concurrent small bowel perforations from metastatic melanoma. This highlights the importance of examining the entire bowel even though an obvious perforation site is found. It is unclear whether the patient’s medication which included steroids and targeted therapy contributed to perforations.

In this case report, the patient was first found to have melanoma diagnosed 12 years ago and found to have had a recurrence in 11 years later with metastatic deposits in brain and inguinal lymph nodes then but only was found to have the metastatic deposits in bowel after her laparotomy. Due to the nature of melanoma, it appears that tumors have to grow larger to develop any symptoms and that can be many years after [2]. This carries a poor prognosis and, as shown above, carries only a median survival of up to six months [10],[11],[12],[13].

In patients with known metastatic melanoma presenting with an acute abdomen, it would be crucial to have strong suspicions that small bowel perforations from metastatic melanoma, although rare, can occur. We present a unique case of concurrent two small bowel melanoma deposits perforations found during surgery, highlighting importance to examine the entire bowel for any other pathologies sites even when site of perforation is found. Primary aim would be to have patient worked up and having prompt surgical treatment.