KIT and PDGFRA in esophageal pure small cell carcinoma

The author herein reports a very rare case of pure small cell carcinoma of the esophagus with an emphasis on KIT and PDGFRA. A 72-year-old man was admitted to our hospital because of dysphagia, and endoscopy showed a tumor in the esophagus. A biopsy of the esophageal tumor showed a small cell carcinoma consisting of malignant small cells with very hyperchromatic nuclei and inconspicuous nucleoli and without any differentiations. An immuno-histochemical study revealed positive reaction for cytokeratin (Dako, Glostrup, Denmark), KIT, PDGFRA, synapto-physin, p53 protein, and CD56, and negative reaction for chromogranin, CD45, CD20, CD3, and CD30. The Ki-67 labeling was 95%. A molecular genetic analysis showed no mutations of KIT and PDGFRA genes. The patient underwent radiation (50 Gray) and chemotherapy (cisplatin, 5 courses), but he developed liver and bone metastases and died of systemic carcinomatosis five months after the initial presentation.