Introduction to the Oncology Care Unit

- Cancer

Cancer is an abnormal growth of cells (typically originating from a single abnormal cell). The cells multiply continuously due to the loss of natural control mechanisms, invade nearby tissues, and spread to distant parts of the body, stimulating the growth of new blood vessels from which cancerous cells derive nutrients. Malignant cancer cells can develop from any tissue within the body.

When cancerous cells grow and multiply, they form a mass of cancerous tissue (a tumor) that invades and destroys the surrounding normal tissues. The term "tumor" refers to abnormal growth or mass. Tumors can be cancerous or non-cancerous. Cancerous cells can spread from their primary sites to other parts of the body (metastasis).

Types of Cancer:
• Carcinoma: Malignant cells in epithelial tissues and the skin.
• Sarcoma: Malignant cells in connective tissues, muscles, and bones.
• Leukemia: Malignant cells in the blood or blood-forming organs.
• Lymphoma: Malignant cells in the lymph nodes.

Malignant cancer tissues can be divided into blood tissues and blood-producing tissues—leukemias, lymphomas, and solid tumors (solid masses of cells). Solid cancerous tumors can be classified into two types: carcinomas and sarcomas. Specific types of cancers can be further classified according to the organ where they first appeared or the type of cell they originate from, for example, squamous cell carcinoma in the skin.

Leukemia and lymphomas affect blood and blood-producing tissues and immune system cells. Leukemia arises from blood-forming cells and leads to an overproduction of normal blood cells in the bone marrow. Cancerous cells from lymphomas lead to enlarged lymph nodes, resulting in large masses in the armpit, upper thigh, abdomen, and chest.

Carcinomas are cancers affecting the cells lining the skin, lungs, digestive tract, and internal organs. Examples of carcinomas include skin cancer, breast cancer, colon cancer, stomach cancer, breast cancer, prostate cancer, and thyroid cancer. Carcinomas occur at higher rates in older individuals compared to younger ones.

Sarcomas are cancers that affect mesodermal cells, which form muscles, blood vessels, bones, and connective tissues. Examples of sarcomas include smooth muscle sarcoma (or smooth muscle cancer found in the walls of the digestive system) and osteosarcoma (bone cancer). Sarcomas occur more frequently in younger individuals compared to older ones.