1. Neoplasia

2. 3- Rate of growth  Most benign tumours grow slowly over a period of years, whereas most cancers grow rapidly, spread locally and to distant sites (metastases) and eventually kill their host.  Host factors influence growth rate. Hormones influence the growth rate, particularly of cancers arising in hormonally-responsive tissue (e.g. breast, uterus, endometrium, ovary and prostate).

3.  Adequacy of blood supply to tumour cells is an important factor for growth of cancers. It is suggested that tumour cells themselves secrete an angiogenesis factor that promotes new vascularization. Without such blood supply, solid neoplasms can't grow beyond 2 to 3 mm in diameter.  There are also unknown influences that may affect the rate of growth.

4.  4- Metastasis  Metastases are tumour implants discontinuous with the primary tumour possibly in remote tissue.  Metastasis marks a tumour as malignant because benign neoplasms do not metastasize. With few exceptions all cancers can metastasize. The major exception is basal cell carcinoma of the skin.  In general, the more aggressive, the more rapidly growing, and the larger the primary neoplasm, the greater the likelihood that it will metastasize.

5.  5-Recurrence after excision: Usually occurs in malignant tumours  6-Fate: A benign tumour is not fatal unless it is present in a vital area; on the other hand a malignant tumour is usually fatal

6. Spread of malignant tumours:  1) Direct spread: into the surrounding structures.  2) Lymphatic spread: along lymphatic vessels to the draining lymph nodes by  a-lymphatic permeation b-lymphatic embolization.

7.  3)Blood spread: This method is favored by sarcoma, because sarcomas are rich in small thin-walled, badly formed blood vessels that are easily penetrated by malignant cells. As veins have thinner walls than arteries, so they are easily invaded by the malignant cells

8.  Sites of blood borne metastases are governed by the anatomical distribution of veins:  cancer of the portal area liver through portal vein.  Cancer of the systemic circulation lung, to the left side of the heart and then anywhere in the body.  Cancer arising in a close proximity to the vertebral column embolizes through the paravertebral plexus (cancer of the thyroid and prostate).

11. Certain carcinomas have a tendency for invasion of veins. Renal cell carcinoma Hepatocellular carcinoma Choriocarcinoma

12. 4)Natural passages: tumour cells are carried along natural passages such as bronchi, ureters, and fallopian tubes. 5)Transcoelomic spread: Through serous cavities such as pleura, pericardium, and peritoneal cavity, e.g. carcinoma of the stomach spreads to the ovaries through the peritoneal cavity. 6)Inoculation: During surgical removal of a malignant tumour, malignant cells may get implanted in the surgical wound. 7)Perineural lymphatics: along the nerves.

13. Differences between benign and malignant tumors FeatureBenignMalignant CapsulationUsually presentUsually absent Mode of growthBy expansionBy infiltration DifferentiationWell differentiatedVariable AnaplasiaAbsentPresent Rate of growthSlowRapid MetastasesDoes not happenMay occur RecurrenceUsually do not recurCommon FateCured by excision ( if not in vital area) Usually fatal

14. Grading and Staging in Cancer  Grading: attempts to establish the aggressiveness of tumour or level of malignancy based on: the cytologic differentiation of tumour cells and number of mitoses within the tumour, i.e grading could be defined as a pathological term denoting degree of differentiation of a malignant tumour.  Cancer is classified into grade I, II, III, and IV in order of increasing anaplasia.

17.  Staging: is assessment of the spread of malignant tumour in the body. This assessment is based on clinical and radiographic examination (CT, MRI), and in some cases surgical exploration i.e. staging could be defined as a clinical term denoting the degree of spread of a malignant tumour.

18. Two methods of staging are in use: a- TNM system  T signifies the extent of the primary tumour in tissues.  N stands for the lymph node involvement.  M stands for distant metastases. b- Stages 0 to IV  Incorporating the size of the primary tumour as well as the presence of nodal spread, and of distant metastases.  N.B: When compared with grading, staging has proved to be of greater clinical value.