Abstract

Background: Primary esophageal melanoma is rare, comprising 0.1-0.2% of all esophageal tumors, and difficult to distinguish from metastatic melanoma. Case: A 79yo female with a history of B-cell lymphoma was referred for an esophageal mass. Upper endoscopy revealed a partially obstructing submucosal mass in the mid-esophagus. Biopsy showed an atypical spindle cell proliferation that was positive for S100, SOX-10, HMB-45 (patchy), MART-1 (patchy), and MiTF but negative for desmin, SMA, CD34, DOG-1, and pancytokeratin. Scattered melanin pigment was present (positive on Fontana-Masson stain but negative on iron stain). Collagen IV highlighted the basement membrane surrounding tumor cell nests focally. BRAF mutation analysis was negative. These findings were consistent with spindle cell melanoma, either metastatic or primary. The patient had no known history of melanoma. No other obvious sites of disease involvement were identified on PET/CT or on brain MRI. Gross examination of the esophagectomy specimen showed a 5.5 cm circumscribed polypoid black mass protruding into the lumen. Microscopically, the tumor was composed of invasive pleomorphic hyperchromatic spindle cells with ribbon-like nuclear palisading and multiple mitoses (6/10 high power fields). Melanoma in situ was present in the mucosa beyond the periphery of the invasive tumor, further supporting an esophageal primary rather than a metastasis. Surgical margins were negative. Eleven resected lymph nodes were negative. Follow-up is not available as this was a recent case. Conclusion: Primary esophageal melanoma is extremely rare and can be difficult to distinguish from metastatic melanoma.

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