This document summarizes key facts about cancer: - Cancer is a leading cause of death worldwide, accounting for nearly 10 million deaths in 2020. The most common cancers are breast, lung, colon, rectum and prostate. - Cancer occurs due to genetic and environmental factors like tobacco use, diet, physical activity levels, and some infections. Many cancers can be cured if detected early and treated. - Cancers are classified as benign or malignant tumors. Benign tumors are not cancerous while malignant tumors are and can spread to other parts of the body through metastasis.

1. Cancer

2. Facts
 Cancer is a leading cause of death worldwide, accounting for nearly 10
million deaths in 2020, or nearly one in six deaths.
 The most common cancers are breast, lung, colon and rectum and prostate
cancers.
 Around one-third of deaths from cancer are due to tobacco use, high body
mass index, alcohol consumption, low fruit and vegetable intake, and lack
of physical activity.
 Cancer-causing infections, such as human papillomavirus (HPV) and
hepatitis, are responsible for approximately 30% of cancer cases in low-
and lower-middle-income countries.
 Many cancers can be cured if detected early and treated effectively.

3.  Cancer is a group of diseases involving abnormal cell growth with the
potential to invade or spread to other parts of the body.
 These contrast with benign tumors, which do not spread

9. Benign tumors
 Benign tumors are those that stay in their primary location without invading
other sites of the body.
 They do not spread to local structures or to distant parts of the body. Benign
tumors tend to grow slowly and have distinct borders.
 Benign tumors are not usually problematic.

10. Malignant tumors
 Malignant tumors have cells that grow uncontrollably and spread locally
and/or to distant sites.
 Malignant tumors are cancerous (ie, they invade other sites).
 They spread to distant sites via the bloodstream or the lymphatic system. This
spread is called metastasis

11.  The spread of cancer cells from the place where they first formed to another
part of the body. In metastasis, cancer cells break away from the original
(primary) tumor, travel through the blood or lymph system, and form a new
tumor in other organs or tissues of the body.

13. Cancer types
 Cancers are often described by the body part that they originated in.
 However, some body parts contain multiple types of tissue, so for greater
precision, cancers are additionally classified by the type of cell that the
tumor cells originated from

14. Carcinoma
 Cancers derived from epithelial cells.
 This group includes many of the most common cancers that occur in older
adults.
 Nearly all cancers developing in the breast, prostate, lung, pancreas,
and colon are carcinomas.

15. Sarcoma
 Cancers arising from connective tissue (i.e. bone, cartilage, fat, nerve), each
of which develop from cells originating in mesenchymal cells outside of the
bone marrow.

16. Lymphoma and leukemia
 Lymphoma and leukemia, these two classes of cancer arise from immature
cells that originate in the bone marrow, and are intended to fully
differentiate and mature into normal components of the immune system and
the blood, respectively.
 Acute lymphoblastic leukemia is the most common type of cancer in children,
accounting for ~30% of cases.
 However, far more adults than children develop lymphoma and leukemia.

17. Germ cell tumor
 Cancers derived from pluripotent cells, most often presenting in
the testicle or the ovary (seminoma and dysgerminoma, respectively).

18. Blastoma
 Cancers derived from immature "precursor" cells or embryonic tissue.
 Blastomas are generally more common in children
(e.g. neuroblastoma, retinoblastoma, nephroblastoma, hepatoblastoma, med
ulloblastoma, etc.) than in older adults.

19.  Cancers are usually named using -carcinoma, -sarcoma or -blastoma as a
suffix, with the Latin or Greek word for the organ or tissue of origin as the
root.
 For example, the most common cancer of the liver parenchyma ("hepato-" =
liver), arising from malignant epithelial cells ("carcinoma"), would be called
a hepatocarcinoma
 While a malignancy arising from primitive liver precursor cells is called
a hepatoblastoma. Similarly, a cancer arising from malignant fat cells would
be termed a liposarcoma.

20.  Some types of cancer are named for the size and shape of the cells under a
microscope, such as giant cell carcinoma, spindle cell carcinoma, and small-
cell carcinoma.

21.  Benign tumors (which are not cancers) are usually named using -oma as a
suffix with the organ name as the root.
 For example, a benign tumor of smooth muscle cells is called
a leiomyoma (the common name of this frequently occurring benign tumor in
the uterus is fibroid). Confusingly, some types of cancer use the -noma suffix,
examples including melanoma and seminoma.

22. Causes
 Cancer arises from the transformation of normal cells into tumour cells in a
multi-stage process that generally progresses from a pre-cancerous lesion to a
malignant tumour. These changes are the result of the interaction between a
person's genetic factors and three categories of external agents, including:
 physical carcinogens, such as ultraviolet and ionizing radiation;
 chemical carcinogens, such as asbestos, components of tobacco smoke,
alcohol, aflatoxin (a food contaminant), and arsenic (a drinking water
contaminant); and
 biological carcinogens, such as infections from certain viruses, bacteria, or
parasites

23. Hallmarks of Cancer: Resisting Cell Death
 One thing we know about cancer cells: they can resist death. They evade
apoptosis, the mechanism that programs cell death once cells become
damaged. Normally, apoptosis helps keep an organism healthy through growth
and development, maintaining body tissue by removing infected or damaged
cells. But cancer cells do not follow this process, no matter how abnormally
they grow.

24.  The cancer cells may alter the mechanisms that detect the damage or
irregularities, preventing proper signaling and apoptosis activation. Cancer
cells may also introduce defects in the downstream signaling itself, or the
proteins involved in apoptosis, which would also prevent proper apoptosis (

25. Hallmarks of cancer