Sentence:  In such diseases as <WSD>cancer</WSD> , tuberculosis , and heart disease , early diagnosis and treatment are so vital that the waste of time by the patient with Doctor Fraud 's cure-all gadget can prove fatal . 
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