Cancer is a group of diseases in which cells grow without normal control, invade nearby tissue, and can spread to distant sites. It develops through accumulated genetic damage: activation of oncogenes (growth accelerators) and loss of tumor suppressor genes (brakes such as TP53, BRCA1/2). Carcinogenesis is usually described in three stages: initiation (irreversible DNA damage), promotion (repeated exposure lets damaged cells multiply — potentially reversible), and progression (invasion and metastasis).
Benign vs. malignant tumors
| Feature | Benign | Malignant |
|---|
| Differentiation | Well differentiated, resembles normal tissue | Often poorly differentiated (anaplasia) |
| Growth | Slow, expansive, often encapsulated | Often rapid, infiltrative, poorly defined borders |
| Spread | No metastasis | Invasion and metastasis |
| Recurrence after removal | Rare | Common |
| Harm | Mainly by pressure or hormone production | Tissue destruction, organ failure, cachexia |
Classification by tissue of origin
| Origin | Name | Examples |
|---|
| Epithelial tissue | Carcinoma | Adenocarcinoma (glandular epithelium: breast, colon, prostate, pancreas, many lung cancers); squamous cell carcinoma (skin, esophagus, cervix, lung) |
| Connective tissue (bone, muscle, fat, cartilage) | Sarcoma | Osteosarcoma, liposarcoma |
| Blood-forming tissue | Leukemia | Acute myeloid leukemia |
| Lymphatic tissue | Lymphoma | Hodgkin and non-Hodgkin lymphoma |
| Plasma cells | Myeloma | Multiple myeloma |
| Nervous tissue | Glioma and others | Glioblastoma |
How cancer spreads
- Direct invasion into neighboring tissue
- Lymphatic spread to regional lymph nodes (common for carcinomas)
- Hematogenous spread through blood vessels (common for sarcomas)
- Seeding across body cavities (e.g., ovarian cancer in the peritoneum)
Common sites of metastasis: bone (breast, prostate, lung, kidney, thyroid), liver (colorectal and other GI cancers via the portal vein), lung, and brain (lung, breast, melanoma).
Major risk factors: tobacco (the leading preventable cause), alcohol, obesity and inactivity, infections (HPV, hepatitis B and C, Helicobacter pylori, Epstein-Barr virus), ultraviolet and ionizing radiation, occupational chemicals, aging, and inherited syndromes (BRCA1/2, Lynch syndrome).
General warning signs to report
- New lump or thickening; a sore that does not heal; a changing mole
- Unexplained weight loss, fatigue, or fever
- Change in bowel or bladder habits; unusual bleeding or discharge
- Persistent cough, hoarseness, or difficulty swallowing
- New, persistent pain — for example, new bone or back pain in a client with known cancer suggests bone metastasis and needs prompt evaluation
Paraneoplastic syndromes — effects caused by substances the tumor secretes, e.g., SIADH with hyponatremia (small cell lung cancer) and hypercalcemia from PTH-related peptide (squamous cell lung cancer).
Performance status describes how well the client functions and guides treatment choices.
| ECOG grade | Meaning |
|---|
| 0 | Fully active |
| 1 | Restricted in strenuous activity; can do light work |
| 2 | Up and about more than 50% of waking hours; self-care but no work |
| 3 | In bed or chair more than 50% of waking hours; limited self-care |
| 4 | Completely disabled; no self-care; confined to bed or chair |
| 5 | Dead |
Tissue diagnosis — the only definitive test
| Method | Description |
|---|
| Fine-needle aspiration (FNA) | Thin needle removes cells for cytology; least invasive, but cannot show tissue architecture |
| Core needle biopsy | Larger needle removes a tissue core; standard first biopsy for most breast masses |
| Vacuum-assisted biopsy | Suction obtains several cores through one insertion |
| Incisional biopsy | Surgical removal of part of the mass |
| Excisional biopsy | Removal of the whole lesion |
| Endoscopic biopsy | Through bronchoscopy, colonoscopy, etc. |
| Bone marrow aspiration and biopsy | Leukemia, lymphoma, myeloma staging |
Imaging
| Test | Main use |
|---|
| CT (chest, abdomen, pelvis) | Most widely used staging test; e.g., abdominal and chest CT for colorectal cancer (liver and lung spread) |
| MRI | Brain, spinal cord, soft tissue, liver, rectum, breast |
| PET-CT | Shows metabolically active tissue; detects distant spread in many cancers (lung, lymphoma, others) |
| Bone scan | Bone metastasis (prostate, breast) |
| Ultrasound, mammography | Breast, thyroid, liver, and guidance for biopsy |
Tumor markers — useful for monitoring response and recurrence, not for making a diagnosis on their own (they can be raised by benign conditions).
| Marker | Main cancer |
|---|
| CEA | Colorectal |
| CA-125 | Ovarian |
| AFP | Liver, germ cell tumors |
| PSA | Prostate |
| CA 19-9 | Pancreatic, biliary |
| hCG | Germ cell tumors, gestational trophoblastic disease |
Molecular testing on tumor tissue (e.g., HER2, estrogen and progesterone receptors, EGFR, ALK, PD-L1, mismatch repair status) selects targeted therapy and immunotherapy. Germline genetic testing identifies inherited risk.
Grading vs. staging
| Grade | Stage |
|---|
| What it describes | How abnormal the cells look (degree of differentiation) under the microscope | Anatomic extent of the cancer in the body |
| Scale | G1 (well differentiated) to G3–G4 (poorly differentiated/undifferentiated) | TNM; overall stage 0–IV |
| Meaning | Higher grade → usually faster growing, more aggressive | Higher stage → more spread, worse prognosis |
TNM staging (AJCC/UICC)
- T — primary tumor: size and depth of local invasion (Tis = carcinoma in situ, T1–T4)
- N — regional lymph nodes: none (N0) to extensive involvement (N1–N3)
- M — distant metastasis: absent (M0) or present (M1)
- TNM groups combine into stage 0 (in situ) to stage IV (distant spread). Clinical staging uses examination and imaging; pathologic staging adds surgical findings. For some cancers, grade and biomarkers are now built into the stage group.
- Hematologic cancers use other systems (e.g., Lugano staging for lymphoma).
Purpose of staging: to choose the most effective treatment, estimate prognosis, and compare results across centers and clinical trials.
- Diagnosis and staging are reviewed by a multidisciplinary team (surgical, medical, and radiation oncology, pathology, radiology, nursing).
- Goals of treatment are set from stage, biology, performance status, and client wishes: cure, control (long-term disease management), or palliation (symptom relief).
- Localized disease often receives surgery or radiation with curative intent; regional disease adds systemic therapy; metastatic disease is usually treated with systemic therapy, with palliative care alongside.
- Restaging after treatment uses imaging and markers; the original stage stays the same for record-keeping, and recurrence is described separately.
Safety for diagnostic procedures
- Biopsy: confirm consent; review anticoagulants and antiplatelets and hold them only as ordered; check platelets and coagulation tests. Afterward: bleeding, hematoma, pain, infection; pneumothorax after lung biopsy.
- Iodinated contrast CT: ask about prior contrast reactions; check kidney function (eGFR); hydrate; follow protocol for metformin, which may be held after contrast in clients with reduced kidney function or acute kidney injury.
- MRI: screen for implanted devices and metal; gadolinium caution in severe kidney disease.
- PET-CT: usually fasting for several hours beforehand; control blood glucose (high glucose reduces image quality); avoid strenuous exercise the day before.
Listed in priority order.
- Physiologic safety during procedures — monitor vital signs, bleeding, respiratory status (after lung or mediastinal biopsy), and contrast reactions; keep emergency drugs available
- Recognize urgent findings — new neurologic deficits or back pain (spinal cord compression), confusion (hypercalcemia or hyponatremia), and facial or arm swelling (superior vena cava obstruction) require prompt reporting
- Pain and symptom management — assess pain with a validated scale and treat promptly
- Emotional support — the waiting period is highly stressful. Use open-ended questions, listen, correct misunderstandings, and avoid false reassurance
- Information and informed decisions — explain the purpose of each test; reinforce the provider's explanation of staging and options; check understanding with teach-back
- Nutrition and function — screen for weight loss and malnutrition; document performance status
- Staging tests help the team choose the best treatment; they do not predict an individual outcome with certainty
- Biopsy aftercare: keep the site clean and dry; report bleeding, increasing swelling, fever, or shortness of breath
- Tumor markers are one piece of information; a single value is interpreted with imaging and examination
- Prevention: stop smoking, limit alcohol, maintain healthy weight, protect skin from sun, and get HPV and hepatitis B vaccines
- Screening (average risk, current US recommendations):
- Breast: mammography every 2 years at ages 40–74
- Cervical: ages 21–29, cytology every 3 years; ages 30–65, cytology every 3 years, high-risk HPV testing every 5 years, or co-testing every 5 years; stop after 65 with adequate prior negative screening
- Colorectal: ages 45–75 by stool-based test or colonoscopy
- Lung: yearly low-dose CT for ages 50–80 with at least 20 pack-years who smoke now or quit within the past 15 years (USPSTF; the American Cancer Society 2023 guideline no longer uses the 15-year limit)
- Prostate: individual decision about PSA testing at ages 55–69
- Know family history; ask about genetic counseling when several relatives had cancer or when cancer occurred at a young age
| Situation | Red flags |
|---|
| Spinal cord compression (metastasis) | New back pain, leg weakness, numbness, bladder or bowel changes — emergency |
| Hypercalcemia of malignancy | Confusion, thirst, polyuria, constipation, weakness |
| Superior vena cava syndrome | Swelling of face and arms, distended neck veins, dyspnea |
| Post-biopsy bleeding or pneumothorax | Tachycardia, falling blood pressure; sudden dyspnea, decreased breath sounds |
| Contrast reaction | Urticaria, wheeze, hypotension |
| Psychological crisis | Hopelessness, statements of self-harm |
- T = primary tumor, N = regional nodes, M = distant metastasis; stage is based on anatomic extent
- Grade = differentiation (how much cells resemble normal); poorly differentiated = more aggressive
- Staging purpose: choose treatment, estimate prognosis
- Biopsy is the only definitive diagnosis; FNA is the least invasive
- Adenocarcinoma arises from glandular epithelium; sarcoma from connective tissue
- Malignant tumors invade, metastasize, and recur; benign tumors rarely recur
- CT is the most widely used staging test; PET-CT detects metabolically active distant disease
- Tumor markers monitor treatment and recurrence; they are not diagnostic alone
- New bone pain in lung, breast, or prostate cancer → suspect bone metastasis
- Colorectal cancer staging needs chest and abdominal imaging (liver and lung spread)
Country Notes
United States
- Screening intervals above follow USPSTF recommendations (breast screening from age 40 was finalized in 2024); insurers generally cover USPSTF grade A and B screening services without cost sharing.
Philippines
- The National Integrated Cancer Control Act (Republic Act 11215, 2019) created a national cancer control program, cancer registries, and financial assistance for cancer care.
- Chronic hepatitis B is a major driver of liver cancer; birth-dose hepatitis B vaccination and screening of adults at risk are key prevention messages.
- In lower-resource settings, cervical screening may use visual inspection with acetic acid (VIA) when cytology or HPV testing is not available.