Small cell carcinoma (non-oat cell type) of the esophagus concomitant with invasive squamous cell carcinoma and carcinoma in situ. A case report.

A case of double primary invasive carcinoma of the esophagus, consisting of well-differentiated squamous cell carcinoma and non-oat cell small cell carcinoma without squamous differentiation, is presented. This is the first reported case of a double or multiple primary invasive carcinoma of the esophagus in which one component is small cell carcinoma (oat cell or non-oat cell). Furthermore, the mucosal epithelium around the non-oat cell small cell carcinoma revealed multiple dysplasia and carcinoma in situ. These lesions were definitely separated from the invasive carcinoma and from each other. The results suggest that pure non-oat cell small cell carcinoma of the esophagus without squamous differentiation is derived from the esophageal squamous epithelium, and is a variant of squamous cell carcinoma.