Primary Gastrointestinal Malignant Melanoma

Abstract

previously healthy, 51-year-old woman was Areferred to our hospital because of a gastric tumor adjoining the esophagogastric junction (EGJ). This tumor was discovered incidentally by an upper gastrointestinal (GI) series in the course of her annual medical check-up. The patient’s history was unremarkable. Physical examination and laboratory work-up showed no abnormalities. An esophagogastroduodenoscopy showed a dark-red EGJ tumor and a black blot accompanied by gray pigmentation scattered over almost the entire esophagus (Figure A and B). An endoscopic biopsy of the lesions showed proliferation of atypical melanocytes, which were immunohistochemically positive for the melanoma-specific antigen HMB-45 (Figure C). Further investigation showed no evidence for other manifestations of the malignant melanoma or metastasis from an extra-GI melanoma into these lesions. Preoperative computed tomography found no local or systemic metastases. The patient underwent a radical surgical resection with gastric tube pull-up. She received no adjuvant therapy although postoperative pathology showed lymph node metastasis in the upper mediastinum. She has been free of recurrence now for 1 year. Microscopically, the EGJ tumor presented some features of a skip lesion because it spread in the direction of the proximal esophageal epithelium and distal gastric mucosa (Figure D, red lines, skip lesions; yellow arrowhead, EGJ). This intraepithelial extension consisting of melanoma cells and atypical melanocytes is called radial growth (Figure E, green arrows), which is a definitive characteristic of primary mucosal melanoma (PMM). Although the exact tumorigenesis was unclear, these