TUMOR GROWTH CAN BE FRACTAL. A curve is fractal if when you look at segments of the curve it appears the same at many different scales of magnification. To be fractal means to be multiply indented, so much so that the curve is said to possess more than a one-dimensional nature. Some fractal curves are so "rough" that they are more like surfaces than lines. The rougher the curve the higher its fractal dimensionality. Scientists have previously found evidence for fractal behavior in curves describing heart fibrillation, forest fires, crystal growth, and many other systems. This applies now also to tumor growth. Antonio Bru of CIEMAT (Madrid) and his colleagues from several labs in Spain (011-34-1-346-6183, bruno@ibm1.ciemat.es) have studied the dynamical behavior of a series of rat brain tumors growing in petri dishes. The morphology results: the tumor profiles are super-rough, with a fractal dimension of 1.21. The dynamical results: the tendency for interface cells to duplicate turns out to be a function of local curvature. The researchers' aim in pinning down the tumor's mathematical parameters is the search for mechanisms that can control and possibly even stop tumor growth. (Bru et al., Physical Review Letters, 2 November 1998.)