Conversion to Neuroendocrine Carcinoma from Squamous Cell Carcinoma of the Esophagus After Definitive Chemoradiotherapy

Background/Aim: Neuroendocrine carcinoma (NEC) of the esophagus is rare and aggressive. We herein report a case of a patient who showed NEC conversion from squamous cell carcinoma (SCC) of the esophagus in the recurrent lesion after definitive chemoradiotherapy. Case Report: The patient was a 57-year-old Japanese male with mid-thoracic esophageal carcinoma diagnosed as SCC with invasion of the submucosal layer. After definitive chemoradiotherapy, the esophageal tumor completely disappeared. Two months later, local recurrence was recognized at the same location and salvage surgery was performed. An immunohistochemical examination of the resected specimen revealed that most of the recurrent tumor had neuroendocrine (NE) differentiation, although a retrospective review of the initial biopsy specimen showed no involvement of NE differentiation. Conclusion: This case is significant not only in bringing attention to the possibility of NEC conversion from SCC after chemoradiotherapy, but also in discussing tumors originating in the esophagus.