Cancer Metastasis and Staging

Routes of Metastasis

• Malignant tumors can spread through:
• Direct spread
• Lymphatic spread (e.g. carcinoma)
• Blood spread (hematogenous) (e.g. sarcoma)

Grading and Staging of Cancer

Grading

• Degree of differentiation of tumor cells in relation to original tissue
• Depends on aggressiveness of cells and number of mitosis
• Cancer classified as grades I to IV with increasing anaplasia

Staging

• Extent of spread of cancer

Complications of Benign Tumors

• Obstruction (e.g. larynx, CNS)
• Cosmetic problems
• May turn into malignant
• May be functioning (e.g. secreting hormones)

Causes of Death in Cancer

• Vital organs destruction (e.g. liver, brain)
• Vital organ obstruction (e.g. CNS, urinary tract)
• Malnutrition (e.g. GIT tumors affecting intake, digestion, and absorption of food)
• Cachexia (a wasting syndrome)
• Anemia (e.g. due to hemorrhage from ulcer)
• Secondary bacterial infection (e.g. toxemia, bronchopneumonia)

Comparison between Carcinoma and Sarcoma

• Carcinoma: malignant epithelial tumor, more common in old age, fungating, ulcerating or infiltrating, firm to hard consistency, less vascular, cells arranged in groups, spreads early by lymphatics, relatively better prognosis
• Sarcoma: malignant mesenchymal tumor, less common in young adults, bulky mass, soft fleshy consistency, highly vascular, cells arranged singly, spreads early by blood, worse prognosis

Laboratory Diagnosis of Cancer

• Gross appearance
• Histological examination
• Fine needle aspiration
• Cytological smears
• Immuno-histochemistry
• D.N.A. analysis
• Flow cytometry
• Tumor markers (e.g. alpha fetoprotein in liver carcinoma)

Definitions and Nomenclature

• Oncology: science of study of neoplasms
• Neoplasia: an spontaneous abnormal new growth which is causeless, aimless and without limitations
• Cancer: malignant neoplasm
• Differentiation: the extent to which tumor cells resemble normal cells
• Anaplasia: lack of differentiation
• Hamartoma: developmental tumor-like malformation

Etiology and Predisposing Factors

• Geographical (and race) distribution:
• USA: more common in males (lung, colon, and prostate) and females (lung, breast, and colon)
• Japan: more common in stomach cancer
• Age: usually more than 55 years, but some tumors can occur in children
• Hereditary factors: close relatives may get the same cancer
• Acquired lesions: can lead to cancer
• Chemicals: smoking, pollution, radiation, and parasites can increase cancer risk
• Physical: ionizing radiation, ultraviolet rays (UVR), and heat can increase cancer risk
• Hormones: estrogen and androgen can increase cancer risk
• Viruses: hepatitis B virus can increase cancer risk
• Nutritional: aflatoxin can increase cancer risk

Classifications

• According to tissue of origin:
• Epithelial tumors
• Connective tissue tumors
• Nervous tissue tumors
• According to behavior:
• Benign tumors
• Malignant tumors

Differences between Benign and Malignant Neoplasms

• Benign tumors: slowly growing, well differentiated, capsulated, less ulceration, hemorrhage, and necrosis, ↓mitoses and vascularity, no metastasis, not fatal
• Malignant tumors: rapidly growing, poorly differentiated, not capsulated, marked ulceration, hemorrhage, and necrosis, ↑mitoses and vascularity, metastasis, fatal

Microscopic Criteria of Malignancy

• Cells are of variable size and shape (pleomorphism)
• Cells are abnormally arranged (loss of polarity)
• Nuclei are:
• Large
• Hyperchromatic
• With prominent nucleoli
• With irregular nuclear membrane
• With many mitotic figures