We detected aberrant Midkine (MK) expressions in human insulinoma and pancreatic cancer tissues by immunohistochemistry, revealing its potential role in tumorigenesis/carcinogenesis. With a nested-touchdown PCR program we were able to detect the tMK in all human tumor/cancer tissues and cancer/tumor cell lines. Detection of MK in the peripheral cells and precancerous lesions implies its potential for early cancer/tumor diagnosis. Furthermore, we have discovered two novel truncations of the MK, tMKB and tMKC, respectively, in the disease specimens. Our data not only provide an efficient methodology potentially for clinical application but also shed light on the molecular mechanism underlying the role for MK in tumorigenesis/carcinogenesis.