[A case of two patients with primary lung cancer secreting CA19-9]

We experienced two primary lung cancer patients who showed high levels of CA19-9 (Carbohydrate Antigen 19-9). One case was small cell carcinoma and the other was adenocarcinoma. In contrast to malignancies of digestive organ origin, rare CA19-9 positive cases are reported in lung cancer. To get evidences that these lung cancer tissues were producing CA19-9, PAP stain (Peroxidase anti peroxidase method: Sternberger) was performed, and positive stains were obtained in tumors surgically removed from these two patients. Especially in a patient who showed very high level of CA19-9 (27,369 U/ml), almost every tumor cell was positively stained. From these findings, we suggest the importance of checking CA19-9 in patients with lung cancer.