An 82-year-old woman presented with a recent history of dysphagia and heartburn. She underwent upper endoscopy which demonstrated a fungating mass extending 10 cm in length and protruding into and filling the lumen. The edges were necrotic and biopsies were obtained from the base of the lesion.
Histology showed discohesive, small to medium sized cells, arranged primarily in solid nests, with focal necrosis (Figure 1). Cytologically, the cells showed scant to moderate amounts of cytoplasm and eccentric, irregular nuclei with prominent nucleoli. There was focal pagetoid involvement of the overlying squamous mucosa (Figure 2).
Immunohistochemical stains were performed and the neoplastic cells were negative for cytokeratin AE1/AE3, cytokeratin cocktail, synaptophysin, chromogranin, p63, thyroid transcription factor 1 (TTF-1), leukocyte common antigen, and other lymphoid markers while they were diffusely positive for CD56. This immunophenotype excluded the possibility of squamous cell carcinoma. Then, stains for malignant melanoma were performed and demonstrated that the neoplastic cells were focally positive for S-100 protein while other MM markers including Melan-A and SOX10 were diffusely positive (Figure 3).
Based on the morphology and immunohistochemical phenotype, and the absence of a primary tumor elsewhere, a diagnosis of primary esophageal melanoma with aberrant expression of CD56 was rendered.
Molecular testing did not reveal a V600E or V600K mutation in the BRAF oncogene or in the C-kit oncogene.
A positron emission tomography (PET) scan was performed and highlighted the mass in the distal esophagus. It also revealed a 2 cm hypermetabolic liver lesion and hypermetabolic gastroesophageal lymph node (Figure 4). This PET scan also incidentally revealed bilateral hypermetabolic thyroid lesions. Fine needle aspiration of the thyroid nodules revealed papillary thyroid carcinoma.
Chemotherapy was initiated with pembrolizumab, a monoclonal antibody that is given for metastatic or unresectable melanoma, but the patient's disease progressed with more extensive hepatic involvement by metastatic disease, and she died shortly thereafter.