Part II. Cancerous Lesions

Part II Cancerous Lesions

2.1 What is Cancer?

Cancer is a group of cells that grows out of control as it replicates. They continue to grow even when the stimulus that caused them no longer exists. Benign tumors grow slowly and are usually harmless, and the cells remain at the original site. Malignant tumors grow quickly and move throughout the body.³²  “Tumors are firm tissue growths or swellings that may occur on the body, protruding from the skin, under the skin, or within the body.^1,31
 

2.2 What Causes Cancer?

“Cancer is caused by damage (mutations) to the individual’s DNA. DNA is like a set of instructions for cells, telling them how to grow and divide properly. When a mutation occurs in the DNA, normal cells will repair the mutation or simply die off. Sometimes the normal cells do not do their jobs, and the affected cells continue to grow and divide. Eventually, a tumor is formed, and it interferes with normal body functions and may spread to other parts of the body.”³⁶ Not all cancers form tumors; for example, leukemia causes abnormal cells in the blood, bone marrow, lymphatic system, and spleen.³⁶

2.3 How do Cancerous Tumors Develop?

Cancerous tumors may develop at any stage of life in any part of the body. To view an excellent slide presentation of cancer growth, please go to http://slideplayer.com/slide/10836190/ to http://images.slideplayer.com/39/10836190/slides/slide_7.jpg  

2.4 Classification of Tumors

A classification describes the type of tissue in which the cancer cells begin to develop.

Here are some common examples of site-of-origin classification:

• Adenocarcinoma–originates in glandular tissue
• Blastoma–originates in embryonic tissue of organs
• Carcinoma–originates in epithelial tissue (i.e., the tissue that lines organs and tubes)
• Leukemia–originates in tissues that form blood cells
• Lymphoma–originates in lymphatic tissue
• Myeloma–originates in bone marrow
• Sarcoma–originates in connective or supportive tissue (e.g., bone, cartilage, muscle)

(Ref: Health communities http://www.healthcommunities.com/cancer-treatment-and-care/cancer-staging.shtml)

A numerical system is used to classify the extent of disease

• Stage 0    Cancer in situ (in place)
• Stage I     Cancer is limited to the tissue of origin. Evidence of tumor growth
• Stage II    Limited local spread of cancerous cells
• Stage III   Extensive local and regional spread
• Stage IV  Distant metastases

(Ref: Health communities http://www.healthcommunities.com/cancer-treatment-and-care/cancer-staging.shtml)

From: Speer: Current Therapy in Avian Medicine and Surgery, 1st Edition, “Advances in Avian Medicine, Section 1, p. 110. Elsevier, 2016