cancer
n. any one of a group of diseases characterized by the unregulated, abnormal growth of cells to form malignant tumors (see neoplasm), which invade neighboring tissues; the abnormal cells are generally capable of spreading via the bloodstream or lymphatic system to other body areas or organs by the process of metastasis. Causes of cancer are numerous but commonly include viruses, environmental toxins, diet, and inherited genetic variations. Cancers are generally classified as carcinomas if they involve the epithelium (e.g., cancers of the lungs, stomach, or skin) and sarcomas if the affected tissues are connective (e.g., bone, muscle, or fat). More than 150 different kinds of cancer have been identified in humans, based on cell types, rate of growth, and other factors. Because cancers can be disfiguring and life-threatening, psychological counseling is often helpful for patients. —cancerous
adj.