Early stage of carcinoma esophagus is diagnosed by

.investigations for carcinoma oesophagus includes 1)barium swallow -shouldering sign and irregular filling defect.RAT TAIL defect in fluoroscopy is typical. 2)oesophagoscopy -to know lesion, extent and types. 3)biopsy -histological evaluation 4)X-ray /CT/MRI/ bronchoscopy/chromoendoscopy/oesophageal endosonography ref: SRB&;s manual of surgery,5th ed, pg no 806