LAUSR

Rationale: Primary malignant melanoma of the esophagus (PMME) is a rare disease with an extremely poor prognosis. In contrast, melanocytosis is a benign condition defined as melanocytic proliferation with melanin deposition. PMME is often accompanied by melanocytosis, but differentiating between them is difficult because of their similar appearance. Patient concerns: Here, we reported 3 PMME cases, 2 with melanocytosis. Diagnoses: Magnifying endoscopy revealed characteristic non-uniform pigmented spots along deformed intrapapillary capillary loops (IPCLs) in PMME, while melanocytosis showed fine granule-like or linearly arranged spots and intact IPCLs. Interventions: The patients underwent endoscopic or surgical resection of each lesion. Outcomes: Histologically, magnified images reflected melanocyte growth. For cases 1 and 2, the patients remained disease-free for 61 and 15 months after endoscopic resection, respectively. In case 3, liver metastases developed two months after surgery, and the patient died from liver failure after six months. Lessons: This is the first report describing differences in magnified views of the 2 diseases, which aids a differential diagnosis.