Primary Esophageal Melanoma with Aberrant CD56 Expression: A Potential Diagnostic Pitfall.

Primary esophageal malignant melanoma (MM) is rare and extremely aggressive. For pathologists, it can be challenging to diagnose and differentiate from other poorly differentiated malignant neoplasms in the esophagus. Complicating this fact, MM can have divergent differentiation and express nonmelanocytic immunohistochemical markers including epithelial markers (cytokeratins) and rarely neuroendocrine markers. Lack of awareness of this fact by a pathologist can lead to an erroneous diagnosis and delay treatment for an already aggressive disease. Herein, we report a case of primary esophageal malignant melanoma with aberrant CD56 expression without accompanying synaptophysin or chromogranin expression.