- Patients with early esophageal or gastric cancer who are undergoing confirmatory endoscopy with biopsy. These cancers must be limited to T1 N0 M0 (tumor invades submucosa with no lymph node involvement and no metastasis) according to the American Joint Committee on Cancer (AJC) Guidelines (1988 or later). Tumors may either be adenocarcinoma or squamous cell cancers. EUS and CT scanning will be required to confirm tumor staging. Tumors must be limited only to the mucosa or submucosa when examined by high frequency c-EUS. Any thickness of tumor lesion is acceptable provided the lesion does not appear to reach the muscularis propria.