CASE 13312 Published on 12.02.2016

Metastatic melanoma of the small bowel

Section

Abdominal imaging

Case Type

Clinical Cases

Authors

Kirsty Ross1 & Catriona Turbet2

Beatson West of Scotland Cancer Centre1,
1053 Great Western Road,
Glasgow G12 0YN, Scotland;
Department of Radiology -
Glasgow Royal Infirmary2,
84 Castle Street, Glasgow G4 0ET, Scotland
Patient

83 years, male

Categories
Area of Interest Gastrointestinal tract, Thorax ; Imaging Technique CT
Clinical History
An 83-year-old patient presented with iron-deficiency anaemia and melaena. He had a previous colectomy for diverticular disease and excision of a superficial malignant melanoma from his left ear 8 years previously (Breslow 1.9mm), pulmonary nodules had also been detected on CT 5 years previously - he was lost to follow-up.
Imaging Findings
CT Thorax/abdomen/pelvis showed two solid masses in the left upper lobe, larger in size when compared to the previous CT: from 11mm to 39mm and 14mm to 47mm. The jejunum immediately distal to the duodenojejunal flexure was markedly abnormal, with nodular wall thickening up to 3.5cm; extending for 10cm and almost circumferential, the mesenteric wall being more severely affected than the antimesenteric. Soft tissue nodules were present anterior to the mass in adjacent mesentery. Large occlusive thrombus within the proximal superior mesenteric vein (extending into the jejunal branch running alongside the affected small bowel loop) and an anastomosis at the rectosigmoid junction were also present.

Post-CT, this patient presented as an emergency with melaena. Oesophagogastroduodenoscopy revealed an exophytic, circumferential mass with active bleeding at the duodenojejunal junction. Biopsies demonstrated features consistent with metastatic melanoma. BRAF testing reported no mutation. Multi-disciplinary team discussion is awaited.
Discussion
Background & Clinical Perspective

Malignant melanoma can exist at any point of the gastrointestinal (GI) tract: with the most common site being the small bowel (SB). [1] Post-mortem studies report that more than 60% of melanoma patients have GI metastases at death; 50% of which occur in the SB. [2] Most patients are asymptomatic and consequently only 1-5% of patients are diagnosed whilst alive. [3, 4] Symptoms can include abdominal pain, GI blood loss, weight loss and rare cases of intestinal obstruction, intussusception and perforation have been reported. Primary intestinal melanoma is extremely rare, accounting for less than 2% of SB melanoma cases. [5] An unknown primary cutaneous tumour site is estimated to occur in 26% of cases. [6]

The high incidence of SB metastases is thought to be a consequence of the chemokine CCR9. CCR9 is expressed on human melanoma cells and participates in the enhanced motility of melanoma cells and is likely a ‘‘homing receptor’’ for melanoma to the small bowel. [7, 8]

Follow-up for treated localised melanoma is dependent on the initial stage. Given this patient’s initial Breslow thickness of 1.9mm, follow‑up should have been considered every 3 months for the first 3 years after completion of treatment, then every 6 months for the next 2 years, and discontinued at the end of 5 years if no recurrence was identified [9.]

Imaging Perspective

Bender et al. studied 32 patients with SB metastases to assess the reliability of radiological methods for detecting these lesions. Metastases were defined as polypoid, cavitary, infiltrating, or exoenteric – with the polypoid pattern most prevalent. Small bowel follow-through demonstrated 32 of 55 metastases (sensitivity 58%), contrast-enhanced CT demonstrated 32 of 48 masses (sensitivity 66%). [10] Other imaging techniques including capsule endoscopy and PET may raise suspicion of SB metastases, however, histological diagnosis through surgical/endoscopic biopsy is necessary for definitive diagnosis. [11]

Outcome

Novel therapeutic strategies, such as immunotherapy and kinase inhibitors, have demonstrated impressive efficacy in metastatic melanoma. Treatment options for the first- and second-line setting include the checkpoint inhibitors, anti-PD1 antibodies (pembrolizumab, nivolumab), ipilimumab, an anti-CTLA4 antibody for all patients, and BRAF/ MEK inhibitor combinations for patients with BRAF-mutant melanoma. Chemotherapy is considered a second-line or bridging-option. Both checkpoint inhibitors and targeted therapy have been shown to prolong progression-free and overall survival compared with chemotherapy. [12] Surgical resection of visceral metastases may be suitable in patients with good performance status and isolated tumour sites. [12, 13]
Differential Diagnosis List
Metastatic melanoma with small bowel and pulmonary metastases
Small bowel adenocarcinoma
Lymphoma
Final Diagnosis
Metastatic melanoma with small bowel and pulmonary metastases
Case information
URL: https://www.eurorad.org/case/13312
DOI: 10.1594/EURORAD/CASE.13312
ISSN: 1563-4086
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