Melanoma Metastasizing to the Small Intestine: A Case Report Illustrating Symptomatic and Asymptomatic Involvement

Abstract

Symptomatic gastrointestinal (GI) involvement of melanoma is rare, however, it is a frequent autopsy finding in patients with primary cutaneous melanoma. We present a case of metastatic cutaneous melanoma with initial asymptomatic jejunal involvement as found on a positron emission tomography (PET) scan, with subsequent duodenal perforation. A 69-year-old man presented to the hospital with a three-week history of worsening headache, dizziness, and vomiting with a history of Clark level III malignant melanoma that was completely excised from the right flank three years ago at the hospital. A magnetic resonance image of his brain revealed a subacute right-sided cerebellar hemorrhage adjacent to a 1-cm nodule. He underwent a right suboccipital craniomy with resection; the biopsy of which revealed metastatic malignant melanoma. A staging positron emission tomography (PET) scan revealed areas of increased uptake of fludeoxyglucose (FDG) in the left lower lung and left upper quadrant of the abdomen abutting the small bowel. Subsequent enteroscopy revealed a 40-mm cratered jejunal ulcer with heaped edges; the biopsy of which also revealed malignant melanoma. Since he had widespread disease, abdominal surgery was deferred, and treatment with ipilimumab and radiotherapy to the brain was initiated. He presented three months later with acute abdominal pain and diarrhea. A computed tomography scan of his abdomen revealed free peritoneal air, and an exploratory laparotomy revealed a mass at the antimesenteric border of the duodenum with a biopsy consistent with melanoma. The perforated area was resected and an end-to-end anastomosis was performed. Unfortunately, our patient had a postoperative intracranial hemorrhage and was referred to palliative care. Our case portrays how malignant melanoma may metastasize insidiously and widely and present as a catastrophe. Melanoma involvement in the GI tract is a poor prognostic marker. Our case offers a unique illustration of both the occult and manifest gastrointestinal involvement of melanoma and underscores the importance of clinical suspicion in patients with a history of melanoma who present with unexplained GI symptoms.

Keywords: acute abdomen; duodenum; jejunum; melanoma; perforation.

Figure 1. Enteroscopy revealing a non-bleeding, large cratered ulcer measuring 40 mm in largest dimension with heaped edges in the proximal jejunum, occupying >75% of the lumen.

Figure 2. Biopsy of the ulcer with hematoxylin and eosin stain, depicting infiltration in a nesting fashion on the left side consistent with metastatic melanoma. Normal mucosa evident on the right.

Figure 3. Similar section to Figure 2. HMB-45 (melanoma associated antigen) immunohistochemistry positive (brown stain) in melanoma cells on the left compared to normal cells on the right.

Figure 4. CT of abdomen showing evidence of thickened bowel as pointed with white arrows, along with pockets of free peritoneal air.