Amelanotic melanoma metastatic to the duodenum

Abstract

A 69-year-old man with a history of hypertension presented with melena for 1 week. Upon presenting at the emergency department, his hemoglobin level was 9.5 g/dL. Esophagogastroduodenoscopy (EGD) revealed an unpigmented bull's eye lesion with central ulceration in the second portion of the duodenum (Figure 1), biopsies of the lesion confirmed a diagnosis of melanoma. Immunohistochemistry staining results were positive for S-100 and HMB-45 (Figure 2).

Abdominal computed tomography revealed liver metastases, lung metastases, and right ureteral tumor. Extensive clinical examination did not reveal any primary cutaneous melanoma. Duodenal melanoma, whether arising primarily or metastatically from an unidentified or regressed primary cutaneous melanoma, remains debatable.

Unfortunately, he had shown poor response to the subsequent treatment of chemotherapy and immunotherapy with pembrolizumab. He died 6 months later. Patients with a previous history of melanoma presented with vague abdominal pain or anemia; it is prudent to conduct a thorough investigation endoscopically or radiologically.¹ Melanoma has a predilection to metastasize to the gastrointestinal (GI) tract, and the most common site of involvement is small intestine. Metastatic melanoma to the duodenum is often diagnosed at an advanced stage where therapeutic options are limited. Clinical suspicion should remain high for any patient having a history of melanoma and developing GI symptoms. The classic finding of metastatic melanoma on endoscopic imaging is a “target or bull's-eye lesion,” but is found infrequently.² Metastatic melanoma to the GI tract may be either pigmented or amelanotic lesions.³ Melanoma can present as ulcerated, flat, or pedunculated lesions that may or may not be hyperpigmented. Endoscopic imaging of innocuous-appearing lesions that undergo biopsy may be shown to be amelanotic metastatic melanoma; magnifying endoscopy may detect some ominous findings in relatively benign-appearing lesions.⁴ Melanoma seen in the GI tract can be floridly pigmented and obvious metastases of the original melanoma, nonpigmented findings that can be easily missed.

The authors declare no conflicts of interest.

Written informed consent was obtained from the patient.