Primary Malignant Melanoma of the Esophagus - Case Report and Review of the Literature

Abstract

Purpose: Introduction: Primary malignant melanoma of the esophagus (PMME) is rare, with a reported incidence of 0.1% to 0.5% of esophageal malignancies and less than 260 reported cases. Case Report: A 59 year-old man presented with progressive dysphagia and weight loss for 2 months. Skin and eye exam were normal. Upper endoscopy (EGD) revealed an 8 cm fungating, darkly pigmented, ulcerated, partially obstructing mass in the lower esophagus. Biopsy showed subepithelial sheets of malignant, medium-sized, mononucleated cells with normal overlying squamous epithelium. Tumor cells were diffusely immunoreactive to HMB-45, Mart-1 and vimentin; weakly reactive to protein S100; and negative to cytokeratin and lymphoid markers. A diagnosis of small cell primary melanoma of the esophagus was made. Exploratory laparotomy confirmed celiac nodes involvement, and thus stage IV melanoma. A covered esophageal stent was placed endoscopically. Patient underwent palliative radiotherapy and chemotherapy. Three months later he presented with hematemesis. EGD revealed a recurrent mass above the stent with an adherent clot. Restenting was suggested, but the patient opted for comfort care and expired six months later. Discussion: Melanocytes occur in 4-8% of normal esophagi; however, PMME is exceedingly rare. The most common endoscopic finding is a polypoid submucosal mass covered by intact squamous mucosa. Pigmentation is present in 75-90% of cases. Satellite nodules are found in 12% of cases. Uncommonly, a fungating mass may be seen, as occurred presently. Endoscopic biopsy is diagnostic in only 50% of cases. EUS-FNA is 90% accurate and should be performed for a pathologic diagnosis when necessary. PMME tends to spread vertically in mucosa and submucosa, only rarely involving deeper layers. Overlying squamous mucosa is usually intact. Esophageal melanomas are amelanotic in 2% of cases. Standard histological diagnosis is difficult; PMME is missed in 50% cases, frequently being initially labeled as a poorly differentiated squamous tumor. On immunohistochemistry PMME stains positive for vimentin, protein S-100, HMB-45, and melan-A; and is negative for cytokeratin AE1/AE3, desmin, and CD117. Wide-margin surgical resection is the only curative option. Mean survival after radical resection is 14.8 months. Radiation therapy, chemotherapy, and immunotherapy can be used in advanced cases. Endoscopic palliation includes: dilation, tumor photodynamic ablation, and stenting. Prognosis is dismal. Mean survival time is 10-14 months. The 5 year survival rate is 4%. Conclusion: PMME is a rare tumor. Diagnosis can be very challenging, and requires multiple biopsies and detailed immunohistochemical analysis.