Magnifying endoscopy simple diagnostic algorithm for early gastric cancer (MESDA-G). First look for a demarcation line. If absent, the lesion is non-cancer. If present, assess irregular MV (IMVP) and/or irregular MS (IMSP) inside the line; either finding means cancer.
MESDA-G example (I). Demarcation line absent → non-cancer. (A) White light: flat reddish mucosa on the posterior antral wall (yellow arrow). (B) Magnifying NBI: gradual change in capillaries and marginal crypt epithelium; no abrupt border.
MESDA-G example (II). Demarcation line present; irregular MV and MS absent → non-cancer. (A) White light: slightly concave reddish lesion on the posterior corpus (yellow arrow). (B) Magnifying NBI: abrupt MV/MS change at the yellow arrows. Inside the line, vessels and marginal crypt epithelium are regular.
MESDA-G example (III). Demarcation line present; irregular MV and MS present → cancer. (A) White light: well-demarcated depressed lesion with irregular redness on the lesser-curvature antrum (yellow arrow). (B) Magnifying NBI (yellow box in A): clear demarcation (yellow arrows). Inside, microvessels form irregular loops; marginal crypt epithelium is irregular or absent.
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