Small cell neuroendocrine carcinoma of the esophagus: report of 6 cases with immunohistochemical and molecular genetic analysis of KIT and PDGFRA.

Small cell neuroendocrine carcinoma of the esophagus (SCNECE) is a very rare, but a highly aggressive tumor. Six cases of SCNECE (0.25%) were found in the 2,438 archival pathologic specimens of esophagus in the last 20 years in our pathology laboratory. The ages ranged from 62 years to 81 years with a mean of 73 years. All cases were male. The presenting symptoms were dysphagia in 5 cases and vomiting in 1 case. The locations were lower esophagus in 4 cases and middle esophagus in 2 cases. Endoscopically, the tumor was ulcerated in 3 cases and polypoid in 3 cases. All the 6 patients were treated by chemoradiation therapy, and the survival ranged from 6 months to 25 months with a mean of 13 months. Histologically, 5 cases were pure SCNECE, 1 case showed triplicate differentiation into small cell carcinoma, adenocarcinoma and squamous cell carcinoma. Immunohistochemically, each SCNECE showed at least one of the neurocrine antigens. Cytokeratins were positive in 6/6, vimentin 0/6, synaptophysin in 4/6, CD56 4/6, neuron-specific enolase 3/6, chromogranin 0/6, p53 protein in 6/6, KIT in 6/6, and platelet-derived growth factor receptor-α (PDGFRA) in 6/6. Ki-67 labeling ranged from 56% to 100% with a mean of 79%. A retrospective genetic analysis using PCR-direct sequencing method in paraffin sections identified no mutations of KIT (exons 9, 11, 13 and 17) and PDGFRA (exons 12 and 18) genes in all the 6 cases.