Cancer Antigen 19-9
Marcadores tumoraisÚltima revisão: 7 de abril de 2026. Abordagem de fontes: contexto padrão de interpretação laboratorial, material médico de referência e orientações clínicas ou de saúde pública quando relevantes.
O que é Cancer Antigen 19-9?
Cancer Antigen 19-9 (CA 19-9) is a carbohydrate antigen—specifically a sialylated Lewis-a blood group antigen—that is found on the surface of certain epithelial cells and shed into the bloodstream. It was originally identified using a monoclonal antibody (1116 NS 19-9) raised against a human colon carcinoma cell line. CA 19-9 is produced by normal pancreatic and biliary ductal cells, as well as gastric, colonic, endometrial, and salivary epithelium at low levels.
CA 19-9 is the most widely used serum biomarker for pancreatic adenocarcinoma. It serves primarily as a tool for monitoring treatment response, assessing surgical resectability, and detecting disease recurrence. CA 19-9 is not recommended as a screening test for pancreatic cancer in the general population due to insufficient sensitivity and specificity. Approximately 5–10% of the population lacks the Lewis antigen and cannot synthesize CA 19-9, making the test uninformative in these individuals regardless of disease status. Biliary obstruction from any cause can markedly elevate CA 19-9, reducing its specificity.
Por que isso importa
CA 19-9 is the most clinically useful serum marker for pancreatic ductal adenocarcinoma. Preoperative CA 19-9 levels help predict resectability—very high values (>1000 U/mL) often indicate unresectable or metastatic disease. Declining CA 19-9 after surgery or chemotherapy suggests treatment response, while rising levels signal disease progression or recurrence. Because CA 19-9 is also elevated in benign biliary obstruction, cholangitis, pancreatitis, and other gastrointestinal conditions, results must be interpreted alongside imaging and clinical findings.
Faixas de referência normais
| Grupo | Faixa | Unidade |
|---|---|---|
| Adults | 0–37 | U/mL |
| Lewis antigen-negative individuals | Undetectable (test not applicable) | U/mL |
As faixas de referência podem variar entre laboratórios. Sempre compare seus resultados com as faixas fornecidas pelo seu local de exame.
O que significam níveis altos de CA 19-9
Causas comuns
- Pancreatic adenocarcinoma
- Cholangiocarcinoma (bile duct cancer)
- Biliary obstruction (benign or malignant)
- Acute and chronic pancreatitis
- Cholangitis
- Colorectal cancer
- Gastric cancer
- Hepatocellular carcinoma
- Cystic fibrosis
- Liver cirrhosis
Possíveis sintomas
- Jaundice (yellowing of skin and eyes)
- Unexplained weight loss
- Abdominal or back pain
- New-onset diabetes in adults over 50
- Loss of appetite
- Dark urine and pale stools
- Nausea
O que fazer: Elevated CA 19-9 requires imaging (typically CT or MRI of the abdomen) to identify the underlying cause. If biliary obstruction is present, CA 19-9 should be re-measured after biliary drainage, as obstruction alone can cause marked elevation. For patients with known pancreatic cancer, serial CA 19-9 is used to monitor chemotherapy response and detect recurrence. Levels >1000 U/mL preoperatively may indicate unresectable disease. Additional workup may include endoscopic ultrasound with biopsy and cross-sectional imaging.
O que significam níveis baixos de CA 19-9
Causas comuns
- Normal physiological state
- Lewis antigen-negative phenotype (5–10% of population)
- Successful cancer treatment
Possíveis sintomas
- No symptoms associated with low CA 19-9
O que fazer: Low or undetectable CA 19-9 is typically normal. In Lewis antigen-negative individuals, CA 19-9 will be undetectable regardless of disease status, and the test should not be used for monitoring. After cancer treatment, normalization of CA 19-9 is a favorable prognostic indicator, though continued surveillance with imaging remains essential.
Quando o exame de CA 19-9 é recomendado?
- Monitoring treatment response in pancreatic cancer
- Assessing surgical resectability of pancreatic tumors
- Surveillance for recurrence after pancreatic cancer surgery
- Helping differentiate malignant from benign pancreatic cysts
- Monitoring cholangiocarcinoma treatment
Perguntas frequentes
Biomarcadores relacionados
Referências e abordagem de revisão
As páginas do glossário de biomarcadores são explicações educativas e devem ser interpretadas junto com as faixas de referência e observações fornecidas pelo seu laboratório e pelo seu médico. Para conhecer nossos padrões editoriais e processo de revisão, veja nossa Política editorial e a nossa revisão de conteúdo.
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Enviar resultados de exames →Aviso médico: Estas informações são apenas educativas e não substituem orientação, diagnóstico ou tratamento médico profissional. As faixas de referência podem variar entre laboratórios. Sempre converse com seu profissional de saúde sobre a interpretação dos seus resultados específicos.