Tumor Markers
Key Information
Monitoring levels of tumor and indicating a recurrence
CEA (Carcinoembryonic Antigen) (Stomach)
Persistent elevated levels indicate residual or recurrent metastatic carcinoma; nonspecific to stomach cancer
CA 19-9 (Cancer Antigen 19-9) (Stomach)
Monitors post-therapeutic gastrointestinal cancer for recurrence; nonspecific to stomach cancer
CA 195 (Cancer Antigen 195) (Stomach)
Detects gastrointestinal cancers; changing level indicates progression or regression of tumor load; nonspecific to stomach cancer
SCC (Squamous Cell Carcinoma Antigen) (Esophagus)
Monitors tumor burden after treatment for squamous cell carcinoma; used in advanced cases; squamous cell specific
5-HIAA (5-Hydroxy-Indol Acetic Acid) (Small intestine)
Quantitative analysis of urine levels; levels above 15 mg/24 hours indicate malignant carcinoid tumors (argentaffinomas), which may also appear in stomach, appendix, or lower intestine
Go to the Tumor Markers page of the Diagnostic Tests module for more information.
Suggested Citation
SEER Training Modules: Tumor Markers. U.S. National Institutes of Health, National Cancer Institute. Cited 21 December 2025. Available from: https://training.seer.cancer.gov.