Oesophageal squamous cell carcinoma mimicking submucosal tumour

Oesophageal submucosal tumours are usually benign. We report a rare case of esophageal squamous cell carcinoma presenting as a submucosal tumour. A 58-year-old man undergoing screening oesophago-gastroduodenoscopy was found to have a smooth-surfaced 0.6-cm sized submucosal tumour in the oesophagus 30 cm from the incisor. Endoscopic ultrasonography showed the tumour to be located in the muscularis mucosa; the lesion was heterogeneously hypoechoic and had a clear boundary. With a provisional diagnosis of leiomyoma, the tumour was removed by endoscopic submucosal dissection. Pathological examination showed it to be a moderately differentiated infiltrating squamous cell carcinoma, with normal overlying squamous epithelium. Immunohistochemistry indicated that it was caused by malignant transformation in mucosal glandular duct epithelium. Positron emission tomography-computer tomography showed no tumour spread to any other site. The patient was treated by oesophageal resection. The clinician should be aware that oesophageal submucosal tumours with smooth overlying mucosa may not always be benign; malignancy must be ruled out.