What is Cancer?
 

Cancer occurs when abnormal cells grow uncontrollably. When these cells form solid masses, they are called tumors or neoplasms. They can be malignant or benign:
 

• Malignant (Cancerous): Can invade nearby tissues and spread to distant organs (metastasis).

• Benign (Non-Cancerous): May grow, but do not invade neighboring tissue or spread throughout the body.

Lung Cancer
 

The leading cause of cancer death worldwide, divided primarily into Non-Small Cell Lung Cancer (NSCLC) and Small Cell Lung Cancer (SCLC).
 

• Common Causes & Risk Factors:

  • Tobacco Smoke: Cigarette, cigar, or pipe smoking and secondhand smoke exposure.

  • Environmental Carcinogens: Radon gas, asbestos, diesel exhaust, and air pollution.

  • Prior Radiation: Chest radiation therapy for previous cancers (e.g., Hodgkin lymphoma or breast cancer).
     

• Key Symptoms:

  • Persistent, worsening cough or coughing up blood/rust-colored sputum (hemoptysis).

  • Chest pain that worsens with deep breathing, coughing, or laughing.

  • Shortness of breath, wheezing, hoarseness, and recurrent respiratory infections (bronchitis or pneumonia).

Thyroid Cancer
 

Cancers developing in the thyroid gland at the base of the neck, most commonly Papillary or Follicular carcinoma.
 

• Common Causes & Risk Factors:

  • Radiation Exposure: Prior radiation treatments to the head, neck, or chest (especially during childhood) or nuclear fallout.

  • Genetic Factors: Inherited genetic syndromes (e.g., Familial Medullary Thyroid Cancer, MEN2).

  • Sex & Age: Female sex (3x more common in women) and ages 20–55.
     

• Key Symptoms:

  • A painless lump or swelling in the front of the neck (thyroid nodule).

  • Hoarseness or persistent voice changes.

  • Difficulty swallowing or breathing, or feeling like a collar is too tight.

Skin Cancers
 

Cancers originating in the cells of the skin, most commonly caused by ultraviolet (UV) radiation from sun exposure or tanning beds. The primary types are Melanoma, Basal Cell Carcinoma (BCC), and Squamous Cell Carcinoma (SCC).
 

Common Causes & Risk Factors:

• Ultraviolet (UV) Radiation: Direct cell damage from sunlight, tanning beds, and sunlamps.

• Sunburn History: Severe, blistering sunburns, especially in childhood or adolescence.

• Physical Traits: Fair skin, light hair/eyes, freckling, and a large number of moles.

• Immune Suppression: Weakened immune system from medications or underlying conditions.
   

• Melanoma Key Warning Signs (The ABCDE Rules):

  • A – Asymmetry: One half of the mole or spot does not match the other half.

  • B – Border: Edges are irregular, ragged, notched, or blurred.

  • C – Color: Ununiform color; shades of brown, black, pink, red, white, or blue.

  • D – Diameter: Spot is larger than 6 mm across (about the size of a pencil eraser), though melanomas can be smaller.

  • E – Evolving: Any change in size, shape, color, or elevation, or new symptoms like bleeding, itching, or crusting.

• Non-Melanoma (BCC & SCC) Symptoms:

  • A firm, red nodule or a flat lesion with a scaly, crusted surface.

  • A pearly, waxy bump, or a flat, flesh-colored/brown scar-like lesion.

  • A sore that bleeds, oozes, crusts over, heals, and then returns.

Gastrointestinal (GI) Cancers
 

Common Causes & Risk Factors:

• Dietary & Lifestyle: High intake of red/processed meats, low fiber diet, heavy alcohol use, tobacco, and obesity.

• Chronic Inflammation & Infections: Inflammatory bowel disease (Crohn's, Ulcerative Colitis), chronic H. pylori stomach infection, chronic Hepatitis B or C infection, or liver cirrhosis.

• Genetics: Hereditary syndromes like Lynch syndrome or Familial Adenomatous Polyposis (FAP).
   

• Key Symptoms:

  • Colorectal Cancer: Persistent change in bowel habits (diarrhea, constipation, or narrowing of stool), bright red or dark blood in the stool, feeling that the bowel doesn't empty completely, and cramping abdominal pain.

  • Stomach (Gastric) Cancer: Persistent indigestion, feeling bloated or full after small amounts of food (early satiety), severe heartburn, unexplained nausea, and vomiting blood or dark "coffee-ground" material.

  • Esophageal Cancer: Difficulty or pain when swallowing (dysphagia), feeling like food is stuck in the throat or chest, chronic heartburn, and hoarseness.

  • Pancreatic & Liver Cancers: Yellowing of the skin and eyes (jaundice), dark urine, pale or clay-colored stools, severe upper abdominal pain that radiates to the back, and unexplained rapid weight loss.

Breast Cancer
 

Common Causes & Risk Factors:

• Hormonal Exposure: Prolonged exposure to estrogen (early menstruation, late menopause, late first pregnancy or no pregnancies, combined hormone replacement therapy).

• Genetic Mutations: Inherited mutations in the BRCA1 or BRCA2 genes.

• Family & Personal History: Personal or strong family history of breast or ovarian cancer.

• Lifestyle: Alcohol consumption, physical inactivity, and postmenopausal obesity.
   

• Key Symptoms:

  • A new, painless lump or thickening in the breast or underarm (axilla)

  • Changes in breast size, shape, or contour

  • Skin changes on the breast (dimpling, redness, puckering, or an "orange peel" texture)

  • Nipple changes, including nipple inversion, scaling, redness, or spontaneous discharge (especially if bloody)

Cervical Cancer
 

Cancers arising from the cervix (the lower part of the uterus that connects to the vagina), almost always linked to persistent high-risk Human Papillomavirus (HPV) infection.
 

Common Causes & Risk Factors:

• HPV Infection: Persistent infection with high-risk human papillomavirus (HPV) strains (especially types 16 and 18).

• Behavioral & Immune Factors: Tobacco smoking, multiple sexual partners, early sexual activity, and a weakened immune system.

• Screening Gaps: Lack of regular Pap smears or HPV screening.
   

• Key Symptoms:

  • Abnormal vaginal bleeding: Bleeding after sexual intercourse, between periods, or after menopause

  • Unusually heavy or prolonged menstrual periods

  • Watery, bloody, or foul-smelling vaginal discharge

  • Pelvic pain or pain during sexual intercourse

Prostate Cancer
 

Cancers developing in the prostate gland, a small walnut-sized gland in men that produces seminal fluid.
 

Common Causes & Risk Factors:

• Age & Genetics: Risk rises significantly after age 50; strong family history or inherited BRCA mutations.

• Race/Ethnicity: Higher incidence and mortality observed in Black men.

• Dietary Factors: Diets high in dairy products and animal fats.

• Key Symptoms:

  • Difficulty starting urination or a weak, interrupted urine stream

  • Frequent urge to urinate, especially at night (nocturia)

  • Trouble fully emptying the bladder

  • Pain or burning during urination or ejaculation

  • Blood in the urine or semen

  • Persistent dull pain in the lower back, hips, or pelvis (if spread to surrounding bones)
     

Blood Cancers (Leukemia)
 

Cancers of the bone marrow and blood-forming tissues that produce abnormal white blood cells, crowding out healthy blood cells.
 

Common Causes & Risk Factors:

• Environmental Exposure: High-dose ionizing radiation or industrial chemical exposure (e.g., benzene).

• Prior Cancer Treatments: Previous chemotherapy or radiation therapy for other malignancies.

• Genetic Conditions: Certain inherited disorders, such as Down syndrome.
   

• Key Symptoms:

  • Persistent fatigue, weakness, or pale skin (anemia)

  • Frequent or recurrent infections

  • Easy bruising, bleeding gums, or frequent nosebleeds (low platelets)

  • Unexplained fevers, severe night sweats, and weight loss

Lymph Cancers (Lymphoma)
 

Cancers that originate in the lymphatic system (Hodgkin and Non-Hodgkin Lymphoma), affecting immune cells (lymphocytes).
 

Common Causes & Risk Factors:

• Infectious Agents: Epstein-Barr Virus (EBV), HIV, H. pylori, or Hepatitis C.

• Immune Dysregulation: Autoimmune disorders (e.g., Rheumatoid Arthritis, Lupus) or immunosuppressive drug therapy.

• Chemical Exposure: Benzene, pesticides, or herbicides.
   

• Key Symptoms:

  • Painless swelling of lymph nodes in the neck, armpits, or groin

  • Drenching night sweats and recurrent low-grade fevers

  • Unexplained weight loss and persistent itchy skin (pruritus)

  • Shortness of breath or chest pressure if enlarged nodes press on the airway

Bone Cancer (Sarcoma / Myeloma / Metastasis)
 

Primary bone cancers start in the bone tissue, while secondary bone cancer spreads from other organs. Multiple myeloma affects plasma cells inside the bone marrow.
 

Common Causes & Risk Factors:

• Primary Bone Sarcomas: High-dose radiation therapy, hereditary syndromes (e.g., Li-Fraumeni, hereditary retinoblastoma).

• Multiple Myeloma: Age (>65), male sex, Black race, family history, exposure to petroleum products/pesticides.

• Secondary Bone Metastasis: Advanced primary cancers elsewhere in the body (commonly breast, prostate, lung, kidney, thyroid).
   

• Key Symptoms:

  • Persistent, deep bone pain that often worsens at night or during activity

  • Swelling, tenderness, or a noticeable mass over a bone or joint

  • Unexplained bone fractures from minor stress or trauma (pathologic fractures)

  • Numbness, tingling, or weakness if a tumor presses on nearby nerves or the spinal cord

Bladder Cancer
 

Cancers arising from the lining inside the urinary bladder.
 

Common Causes & Risk Factors:

• Tobacco Use: Smoking is the leading cause (carcinogens filter through the kidneys into urine stored in the bladder).

• Occupational Exposures: Industrial chemicals like aromatic amines used in dye, rubber, leather, and paint manufacturing.

• Chronic Bladder Irritation: Long-term catheter use or chronic urinary tract infections.
   

• Key Symptoms:

  • Blood in the urine (hematuria): Urine may look pink, red, or cola-colored (often painless)

  • Painful or burning urination (dysuria)

  • Frequent urination or feeling an urgent need to urinate

  • Pelvic pain or inability to pass urine in advanced stages

Kidney Cancer (Renal Cell Carcinoma)
 

Cancers originating in the microscopic filtering tubules of the kidneys.
 

Common Causes & Risk Factors:

• Lifestyle: Tobacco smoking and obesity double the risk.

• Hypertension: Chronic high blood pressure (regardless of medication treatment).

• Renal Stress & Genetics: Long-term dialysis, workplace exposure to cadmium, or inherited conditions like von Hippel-Lindau (VHL) disease.
   

• Key Symptoms:

  • Blood in the urine (pink, red, or dark)

  • Persistent pain in the side, flank, or lower back that doesn't go away

  • A lump or mass felt on the side or lower back

  • Unexplained weight loss, fever, anemia, and chronic fatigue

Brain & Central Nervous System Cancer
 

Tumors arising directly in brain/spinal cord tissue (Glioma, Meningioma) or spreading from other organs (Metastatic). Most meningiomas are benign, while most gliomas are malignant or premalignant. 
 

• Common Causes & Risk Factors:

  • Primary Tumors: High-dose ionizing radiation to the head; rare genetic syndromes (e.g., Neurofibromatosis, Li-Fraumeni). Most primary brain tumors have no clear environmental cause.

  • Secondary (Metastatic) Tumors: Spread from primary lung, breast, melanoma, renal, or colon cancers.
     

• Key Symptoms:

  • New or Changing Headaches: Severe, persistent headaches that are often worse in the morning or wake you from sleep.

  • Neurological Deficits: Sudden weakness, numbness, or tingling on one side of the body; difficulty speaking, seeing, or walking.

  • Seizures: Unexplained onset of seizures or convulsions in an adult with no prior seizure history.

  • Cognitive Changes: Personality changes, confusion, memory loss, or unexplained nausea/vomiting.
     

Uterine / Endometrial Cancer
 

Cancers originating in the lining of the uterus (endometrium).

Common Causes & Risk Factors:
 

• Estrogen Imbalance: Unopposed estrogen (high estrogen with low progesterone), obesity (fat tissue converts hormones to estrogen), late menopause, or tamoxifen therapy.

• Reproductive History: Never having given birth (nulliparity).

• Genetics: Lynch syndrome (hereditary nonpolyposis colorectal cancer).
   

• Key Symptoms:

  • Abnormal vaginal bleeding: Any bleeding after menopause, or heavy/irregular bleeding between periods

  • Abnormal, watery, or foul-smelling vaginal discharge

  • Pelvic pain, pressure, or cramping

  • Pain during sexual intercourse
     

                                                              References & Guidelines
 

• National Cancer Institute (NCI). Cancer Types, Causes and Risk Factors, Symptoms, Diagnosis, and Treatment.

• American Cancer Society (ACS). Signs and Symptoms of Cancer; Cancer Risk and Prevention.

• Centers for Disease Control and Prevention (CDC). Cancer Prevention and Control.

• National Comprehensive Cancer Network (NCCN). Guidelines for Patients — Cancer Screening, Diagnosis, and Treatment.