Simultaneously two independent tumors were detected in the esophagus. Histological examination could not necessarily distinguish the two tumors from double cancers. It is emphasized that cellular DNA analysis by using FCM is of great benefit for this purpose. It is difficult to determine clinically whether double cancers are simultaneously existing two cancers or cancerous lesion accompanying metastatic lesions. Until recently histologic finding was the only method to identify them. The criteria of identifying double cancers from primary cancer with metastasis are that different types of histology should be individually revealed and no histologic sequence between both. lesions should be defined with or without submucosal lymphatic involvement. It is well known that malignant tumors are characterized by abnormalities in cellular DNA content. However, it is no doubt that metastatic tumors arising from the primary one display a similar pattern of DNA, suggesting identical stem cells with an original tumor when surgeons encounter in independent cancerous lesions in the same surgical specimen, two separated cancerous lesions should be identified whether double primary cancers or metastasis. Flow cytometry (FCM) provides a fast and precise means for determination of DNA-aneuploidy index. we experienced with independent double cancerous lesions in the esophagus and these were regarded as primary cancer with skipping metastatic lesions with the help of analysis of DNA histogram
