Metastatic melanoma localized to the small bowel: a case report

Clinical History

The patient came to our attention because of the onset (for one month) of non-specific abdominal pain. His medical history is noted due to melanoma, on the right thigh, surgically removed. Subsequently the patient was subjected to adjuvant chemotherapy.

Imaging Findings

A Computed Tomography (CT) examination was performed after oral administration of isotonic solution and intravenous contrast medium injection.
Pathologic wall thickening areas with characteristic of hypervascular enhancement were found (Fig. 1, 2a, b). Recognized lesions were in the jejunal loops (which presents an aspect of initial intussusception), and in the first portion of the ileum. There was thickening of the adjacent adipose tissue. Multiplanar reconstructions of coronal sections of the lesions were also evaluated (Fig. 3 a, b).
Positron Emission Tomography (PET) (performed with the radiopharmaceutical fluorodeoxyglucose 18F-FDG) showed multiple areas of glucose hypermetabolism in the context of some small-bowel loops (Fig. 4). The greater intensity of uptake presented maximum Standard Uptake Value (SUV) of 17.
After surgical removal of the affected sections of the small intestine, histological analysis was performed. The fragments analyzed were evaluated as metastatic melanoma and immunohistochemical analysis showed positivity for MART1. The removed lymph-nodes were free from tumour infiltration.

Discussion

Intestinal melanomas are due to primary tumours or metastases of cutaneous, ocular, or anal melanomas. Primary intestinal melanoma is extremely rare and seems to be associated with a worse prognosis and a more aggressive behaviour. Metastatic melanoma of the small bowel results from the tendency of cutaneous melanoma to metastasise to the gastrointestinal tract [1, 2].
Bender et al. [3] defined four different types of metastatic melanoma of the small bowel: cavitary, infiltrating, exoenteric, and polypoid (often called “target” or “bull’s-eye” lesion). Moreover, melanoma metastasis may be either pigmented or amelanotic.
Although small-bowel metastases are found at postmortem examination in up to 60% of patients who died owing to melanoma, antemortem diagnosis is hardly and rarely done.
Clinical presentation of this pathology is similar to other types of gastrointestinal tumours [4]. It is often asymptomatic and eventual symptoms may include chronic abdominal pain (17–64%), occult or massive bleeding (26–84%) and weight loss (10–47%) [1].
Diagnosis of intestinal melanoma is obtained by abdominal ultrasound (US), conventional barium contrast studies, endoscopy, Computed Tomography (CT), or Positron Emission Tomography (PET) [4]; however, the rate of clinical detection is low (only 10–20%). Transabdominal US is the first diagnostic procedure, because it is non-invasive, inexpensive, easily accessible, and does not need special preparation of the patient. However, US alone is often not sufficient to confirm the diagnosis.
Contrast-enhanced CT allows good visualisation of bowel loops and can detect extraluminal findings of intestinal melanoma. Despite these characteristics, the sensitivity of CT imaging in the detection of intestinal melanoma is only 60-70%.
Capsule endoscopy (CE) can investigate segments of the intestine that cannot be otherwise inspected by conventional endoscopy [5].
To detect gastrointestinal metastases, whole-body PET imaging with fluorodeoxyglucose, combined with CT imaging has higher sensitivity and specificity than conventional CT.
A wide intestinal resection, including also the resection of the mesentery with lymph nodes, remains the treatment of choice, associated with low morbidity and mortality rate. In case of obstruction, perforation, or serious haemorrhage an emergency surgical treatment is mandatory [6].
Patients who are candidates for surgery are selected by diagnostic imaging: number and extension of metastatic lesions in the small intestine, including presence of other extraintestinal metastases, and general health of the patient have to be considered in order to perform surgery.
Palliative treatment of metastatic disease includes chemotherapy, immunotherapy or biochemotherapy.

Differential Diagnosis List

Final Diagnosis

Small bowel metastases from melanoma

URL:	https://www.eurorad.org/case/10452
DOI:	10.1594/EURORAD/CASE.10452
ISSN:	1563-4086