Gastroduodenal Metastases from Melanoma
The man had a history of a grade IIB malignant melanoma, which had been resected 5 years earlier. He also had arterial hypertension, type 2 diabetes, and had been taking aspirin, metformin, a statin, and 3 drugs for hypertension.
Upper gastrointestinal endoscopy revealed multiple gastric and duodenal nodular lesions, 20 mm or less in diameter, with a pigmented and ulcerated center. Biopsies were collected, and histopathology analysis revealed invasion of the gastric and duodenal mucosa by neoplastic pigmented cells, which were positive for melan-A (MLANA) in immunohistochemical analyses (see figure).
Positron emission tomography revealed multiple hypercaptant lesions in the patient’s brain, nasopharynx, base of the tongue, lungs, abdominopelvic cavity, skeleton, and subcutaneous tissue of the buttocks and thighs. Magnetic resonance imaging of the brain showed a right frontal cortical lesion and 2 smaller lesions in the right fronto-opercular region and right frontal paramedian region.
The biopsied metastases tested positive for mutations in BRAF. The patient received holocranial radiotherapy and vermurafenib and cobimetinib. He remained anemic and required transfusional support despite oral antacid therapy. The patient died of complications of metastatic disease 3 months after the diagnosis.
Pita et al explain that melanoma frequently metasasizes to stomach; almomst 45% of patients with melanoma were found to have gastrointestinal tract metastases in a postmortem study. These can involve the small bowel, colon, stomach, and esophagus, in descending order of frequency. During endoscopy, melanoma metastases appear as submucosal nodules with central ulcerations. However, lesions present with varying degrees of ulceration and pigmentation, making histologic examination imperative.