Question: What diagnosis code can we submit for malignancy in the lower third of the esophagus? Ohio Subscriber Answer: You submit ICD-10-CM code C15.5 (Malignant neoplasm of lower third of esophagus) when your physician documents malignancy in the abdominal sections of the esophagus. Abdominal esophagus implies the lower third of the esophagus. Tip: You report C15.3 (Malignant neoplasm of upper third of esophagus) and C15.4 (Malignant neoplasm of middle third of esophagus) for malignancy in the upper and middle thirds of the esophagus, respectively.