Mixed neuroendocrine–non‐neuroendocrine neoplasm arising from long‐segment Barrettʼs esophagus showing exceptionally aggressive clinical behavior

BACKGROUND: There is only one report of Barrett's esophagus (BE) with mixed neuroendocrine–non‐neuroendocrine neoplasm (MiNEN). Herein, for the first time, we present a case with an aggressive esophageal MiNEN, as well as with both primary MiNEN and conventional adenocarcinoma, arising in BE. CASE: A 68‐year‐old woman had been diagnosed with 0‐IIa type adenocarcinoma in the background of long‐segment BE, 45 months earlier. She underwent endoscopic submucosal dissection (ESD) and the pathological diagnosis was tubular adenocarcinoma, well‐differentiated, with slight submucosal invasion. There was no lymphovascular invasion and the margins were intact. The upper esophagogastroduodenoscopy conducted the year after ESD showed no residual or recurrent cancer. However, she was subsequently followed up at another hospital, and endoscopy was not performed after the second year. She was urgently transported to our hospital due to buttock pain in the ninth month of the fourth year. A computed tomography (CT) of the head showed multiple cerebral metastases and positron emission tomography–CT revealed numerous osseous and nodal involvements. We performed upper endoscopy and detected type 3 esophageal tumor. Multiple biopsy specimens histopathologically contained invasive neoplasm composed of neuroendocrine carcinoma (NEC) and adenocarcinoma, moderately to poorly differentiated. The NEC element showed diffuse proliferation of primitive cancer cells possessing fine‐granular cytoplasm and nuclei with prominent nucleoli, whereas the adenocarcinoma component had tubules or nested growth of basophilic cells. Immunohistochemically, the NEC cells were diffusely positive for synaptophysin, with focal expressions of INSM1, chromogranin A and NCAM, whereas the adenocarcinoma cells were mostly negative for these NE markers. The Ki67 index was 90% at the hot spots in both types. The patient died 3.5 months after the biopsy‐based histological diagnosis. CONCLUSION: Appropriate therapy according to the guidelines and/or meticulous clinical follow‐up based on periodic endoscopy as well as a full physical examination are essential, from a proactive perspective, for early diagnosis of secondary aggressive cancers after ESD.