Targeting Intralymphatic Tumor Cells (IMAGE) University of Helsinki Caption When a patient is diagnosed with cancer, the primary tumor and metastatic lymph nodes are routinely removed in surgery (blue). However, tumor cells (green) in transit in the lymphatic vessels are left behind as a putative source of local tumor relapse, such as in-transit metastasis in melanoma. Photodynamic therapy (PDT) (red) allows for the destruction of tumor-draining lymphatic vessels and the intralymphatic tumor cells. The image in the inset shows an inflated lymphatic vessel (purple) filled by human cancer cells (green) that have escaped the primary tumor, implanted in the mouse ear, along the lymphatic vessels. The cancer cells lodged inside the lymphatic vessel have begun stimulating the growth of surrounding blood vessels (red), indicating that the microscopic tumor nodule is rapidly growing into a visible tumor. Credit Tuomas Tammela Usage Restrictions Only in this context. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.