Primary malignant melanoma of the esophagus (PMME) has been reported to be a rare and highly malignant disease, and to date a standard treatment strategy has not been established due to limited evidence. The aim of the present study was to investigate the clinicopathological characteristics of this extremely rare disease. A total of 6 out of 2,093 patients with PMME treated in our institution between 1995 and 2016 were retrospectively analyzed and their clinicopathological parameters including treatment course and long-term survival were investigated. The major clinicopathological characteristics of patients were that they were >70 years of age, male sex, dysphagia at first diagnosis, and macroscopic black protruding tumors located in the lower third of the thoracic esophagus. Four of the five patients receiving pretherapeutic endoscopic biopsy were correctly diagnosed with PMME, and two patients received preoperative treatment with ineffective histopathological responses. There were two unresectable cases, one was treated with an immune-checkpoint inhibitor and the other received palliative care. Three of the four patients receiving curative surgery developed hematogenous recurrence within two years of surgery and only one patient with pT1aN0M0 achieved long-term survival. The median overall survival of all six patients was 19.6 (6.4-40.5) months. Patients with stage I disease exhibited significantly more favorable prognoses than those with stage II-IV (P=0.025) and surgically-treated patients had significantly better prognoses than those who did not receive surgery (P=0.018). In conclusion, PMME was associated with highly malignant features and tended to develop hematogenous metastases even after radical resection. Early diagnosis appears to be important to cure this refractory disease.
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