Fleming says gastrointestinal hormones, insulin levels, and the physiology of lymphatic flow in obese patients may contribute to the spread of the tumor cells.

CNN: Obese may be less likely to survive pancreatic cancer

Puzzling over this odd result, he speculated that the smaller injections must be missing rare stem cells and that therefore these cells must be required for the long-term survival and spread of a tumor.

FORBES: Cancer Killer

His strategy is unusual among cancer researchers, who have tended to focus on identifying cancer-causing genes rather than writing differential equations to describe the rate of tumor spread.

FORBES: Ideas & Opinions

In stage IIIB breast cancer, a tumor of any size has spread to tissues near the breast the skin and chest muscles and may have spread to lymph nodes within the breast or under the arm.

CNN: Breast cancer staging

For women who get the dreaded positive result, the next steps are determined by the type of tumor -- how big it is, how much it has spread, how fast it's growing -- as well as by the gestational age of the fetus.

CNN: Pregnant with cancer

But unlike solid-mass tumors, glioblastomas have tiny tentacles that spread into the brain, making it impossible for a surgeon to remove every bit of the tumor.

FORBES: Taking on a Monster

In one patient whose cancer spread on crizotinib, doctors were able to treat the brain tumor with radiation while the rest of the tumors remained under control with the drug.

FORBES: Pfizer Drug Powers Cancer Treatment Into The DNA Age

Kidney cancer had spread to his lungs and one tumor became so big it ate through his sternum and bulged right through the surface of his skin.

FORBES: Novartis Steals The Show