Sentence:  Here there may be an analogy with <WSD>cancer</WSD> : we can detect cancers by their rapidly accelerating growth , determinable only when related to the more normal rate of healthy growth . 
Meaning of the word marked with <WSD> tags:  any malignant growth or tumor caused by abnormal and uncontrolled cell division; it may spread to other parts of the body through the lymphatic system or the blood stream