Hint: Cell is the structural and functional unit of life. Abnormal conditions like high temperature, harmful radiation and certain types of chemicals cause abnormal growth of cells which move to other parts of the body and cause disease.
Neoplasm is undifferentiated cells which do not adhere with one another like a normal cell. This cell causes tumours which disrupt the functioning of normal cells.
Tumour is of two types, benign and malignant. A benign tumour is a non-cancerous tumour, in which cells stop division after reaching a certain size. It causes little damage to the body because the growth of the cell is low. A malignant tumour is a cancerous tumour which shows indefinite growth cause metastasis. This tumour passes to other body parts through blood and lymph. A malignant tumour is fatal because it disrupts the function of vital organs. Cancer is of four types: carcinomas, melanomas, sarcomas and leukaemias. Carcinomas are cancers of epithelial tissue like skin, glands, and epithelial lining of internal organs. Melanomas are caused due to melanocytes of skin and other organs. Sarcomas are cancerous growth mesodermal tissue like bone and cartilage, it is one of rare cancer. Leukaemias are also known as blood cancer caused by cancer of hematopoietic cells which increase the number of leukocytes. This tumour enters various body parts, causing damage and bleeding.
Cancer caused by chemicals, radiations like UV rays and X rays, repeated friction and irritation of body surface, and by certain parasites. Treatment of cancer includes surgery, radiation therapy, chemotherapy and immunotherapy.
Note: The nucleus of the cancerous cell becomes irregular and granular after metastasis, a number of lysosomes also increases which lead to the production of high melanin, mucus and fat droplets. The number of mitochondrial cristae decreases by which cell death is inhibited.