The present invention relates to a method aiding in the assessment of cancer. It discloses the use of the human fibroblast activation protein (FAP/seprase) as a universal marker of different cancer types. Seprase aids in the assessment of pulmonary or lung cancer (LC) or of colon cancer, e.g., of non-small cell lung carcinoma (NSCLC) or colorectal cancer (CRC), but also likely of other specific types of cancer. Such specific cancer types are, e.g., esophagus, head and neck cancer, stomach cancer, bile duct cancer, pancreas cancer, kidney cancer, cervix cancer, ovary cancer, breast cancer, bladder cancer, endometrium cancer or prostate cancer. Furthermore, it especially relates to a method for assessing cancer from a liquid sample, derived from an individual by measuring seprase in said sample. Measurement of seprase can, e.g., be used in the early detection of cancer or in the surveillance of patients who undergo surgery.