Understanding Tumors and Carcinogenesis

Benign Tumors

• Do not spread to nearby tissues
• Can be removed and usually do not grow back
• Can be large and cause serious symptoms
• Can be life-threatening in the brain

Malignant Tumors

• Characterized by more than 2 abnormal cells with abnormal chromosomes
• Invade neighboring tissues and metastasize
• Lack contact inhibition
• Do not form intracellular junctions
• Grow rapidly

Tumors with Borderline Behavior

• Not yet invasive but could become malignant
• Also known as carcinoma in situ
• Confined to the origination layer of cells without invading deep tissues

Metastatic Tumors

• Malignant cancer cells spread from the original tumor to other parts of the body, forming new tumors
• Secondary tumors comprise the same type of cancer cells as the primary tumor

Carcinogenesis

• A three-step cellular process: initiation, promotion, and progression.

Initiation

• The first step of carcinogenesis where normal cells are exposed to carcinogens, causing DNA damage
• These mutations are usually not significant until the second step.

Promotion

• Repeated exposure to promoting agents causes abnormal or mutant genetic information expression
• Changes proto-oncogenes into oncogenes (genes that cause cancer) turning cellular growth "on"
• Affects tumor suppressor genes by turning them "off," removing the ability to regulate cell growth and proliferation
• Loss of suppressor gene function leads to the loss of the ability to perform apoptosis
• P53 gene alteration can decrease apoptotic signals, decreasing mutant cell death

Progression

• Cellular changes from initiation and promotion exhibit increased malignant behaviors.
• Invades adjacent tissues and metastasizes.
• The process of invasion relies on mechanical pressure from the tumor.
• The tumor destroys surrounding tissues and vascular membranes through destructive enzymes.

Metastasis

• Spread of cancer cells.
• Lymphatic spread is the most common mechanism of metastasis.
• Other methods of metastasis include hematogenous spread, angiogenesis, direct extension, and seeding or diffusion.

Etiology

• Etiology is the study of the causes of diseases.
• Physical agents - radiation, excessive sunlight exposure.
• Chemical agents - tobacco use, drugs, toxic and chemical wastes.
• Viruses and bacteria - these can alter a cell's DNA, causing cancer, for example, HPV infection.

Primary Prevention

• Quit smoking and reduce alcohol consumption.
• Avoid excessive sun exposure.
• Participate in lay forums and support groups.

Secondary Prevention

• Breast cancer: Mammography is the diagnostic test of choice for women over 40.
• Cervical cancer: Between the ages of 21-29, Pap Smear tests are recommended.
• Between the ages of 30-65, testing for Human Papillomavirus (HPV) DNA is performed.
• Colorectal cancer: Guaiac tests detect small amounts of blood in stool.
• A colonoscopy is recommended for men and women over 50.

Diagnostics

• Used to determine the presence and extent of cancer
• Determine possible disease metastasis
• Evaluate body systems and involved organs
• Obtain tissues and cells for analysis, including tumor grade and stage

Treatment Options

• Surgery - removes detectable tumors.
• Radiation - delivers high-energy rays to destroy cancer cells.
• Chemotherapy - uses drugs that destroy rapidly dividing cells.
• Immunotherapy - uses the body's immune system to fight cancer.
• Hormone therapy - uses hormones to target certain cancers.

Breast Cancer

• Often begins as a hard, painless, fixed nodule in the upper outer quadrant of the breast.
• Mostly adenocarcinoma tumors, originating from ducts and lobes.
• The Philippines has the highest incidence of breast cancer in Asia.
• The TNM staging system is used to assess breast cancer:
  • T: describes tumor size and location.
  • N: describes lymph node involvement.
  • M: describes metastasis.
• Common sites of metastasis include: bones, lungs, brain, liver.

Breast Cancer Management

• Diagnosis and treatment are dependent on tumor staging, patient age, and overall health.
• Depending on the stage, surgery, radiation.
• Chemotherapy can be used pre-operatively to reduce tumor size or post-operatively to eliminate remaining cancer cells.