Carcinoma in situ of stomach

This code signifies the presence of abnormal, pre-invasive cancerous cells confined to the glandular or surface epithelium of the stomach, without evidence of invasion into the lamina propria or deeper tissues. It represents the earliest stage of gastric cancer, often referred to as stage 0.

Apply this code when pathology reports confirm carcinoma in situ of any part of the stomach. Documentation must explicitly state "carcinoma in situ," "intraepithelial neoplasia grade III," or "high-grade dysplasia" of the gastric mucosa, with no evidence of invasion.

• Distinguish carefully from malignant neoplasm of the stomach (C16.-), which indicates invasive cancer.
• Do not use for benign polyps or low-grade dysplasia; these have different coding assignments.
• Ensure the pathology report clearly specifies "in situ" to avoid overcoding to an invasive malignancy.