Does the cell number 10⁹still really fit one gram of tumor tissue?

A tumor reaching the size of 1 cm(3) (approximately 1 g wet weight) is commonly assumed to contain 1 x 10(9) cells. This paper comments on the probable origin of this "magic" number and on some possible reasons why it has remained in use until now. However, mostly in epithelial tumors (85% of all human tumors) a cell number one order of magnitude smaller would be more realistic.