Cancer Epidemiology 

-  The only certain way to avoid cancer is not to be born, to live is to incur the risk. 

-  Thus, In USA one in five deaths is due to cancers. Over the years cancer incidence increased in males while it slightly decreased in females (due to largely screening Procedures-cervical, breast etc.). In the studied populations the most common cancer in males is broncogenic carcinoma while breast carcinoma in females.

-  Most cancers in adults occur in those over 55 years of age. 

-  Children under 15 years of age however, are susceptible to acute leukemia, central nervous system tumours, neuroblastoma, wilm's tumour, retinoblastoma, rhabdomyosarcoma and etc. Acute leukemias and neoplasms of the central nervous system accounts for about 60% of the deaths. 

Geographic factors (geographic pathology):

Specific differences in incidence rates of cancers are seen worldwide.For example, 

Stomach carcinoma  - Japan

Lung cancer    - USA

Skin cancer  - New zeland & Australia 

Liver cancer     - Ethiopia 

Environmental factors (occupational hazards) include:

Asbestos-----Lung cancer, mesothelioma,esophagus and, stomach carcinomas; 

Vinyl chloride----Angiosarcoma of liver  

Benzene ---Leukemias

Cigarette smoking-----Brochogenic carcinomas 

Venereal infection (HPV)--Cervical carcinoma

Premalignant disorders

a) Heredity premalignant disorders

Inherited predisposition to cancer is categorized in to three groups: 

i. Inherited cancer syndromes  (Autosomal dominant) with strong familial history include

-  Familial retinoblastomas usually bilateral, and a second cancer risk particularly osteogenic sarcoma. Oncosupressor gene is the basis for this carcinogenesis

-  Familial adenomatous polyps of the colon. virtually all cases are fatal   to develop carcinoma of the colon by the age of 50.

 ii. Familial cancers: 

Evidence of familial clustering of cancer are documented  E.g. Breast, ovarian, colonic, and brain cancers

iii. Autosmal recessive syndromes of defective DNA repair Characterized   by chromosomal or DNA instability syndrome such as xeroderma pigmentosium, Ataxia telaangietasia, Bloom syndrome and Fanconi anemia 

B) Acquired preneoplastic disorders 

-  Regenerative, hyperplasic and dysplastic proliferations are fertile soil for the origin of malignant neoplasms. 

Endometrial hyperplasia     - endometrial carcinoma

Cervical dysplasia  - cervical cancer

Bronchial dysplasia  - bronchogenic carcinoma

Regenerative nodules  - liver cancer 

-  Certain non-neoplastic disorders may predispose to cancers. 

Chronic atrophic gastritis  - gastric cancer

Solar keratosis of skin  - skin cancer

Chronic ulcerative colitis   - colonic cancer

Leukoplakia of the  oral cavity, vulva and penis   - squamous cell carcinoma

-  Certain types of benign neoplasms

Large cumulative experiences indicate that most benign neoplasms do not become malignant. However, some benign neoplasms can constitute premalignant conditions.

For example:

Villous colonic adenoma  - Colonic cancer .

References

Bezabeh ,M. ; Tesfaye,A.; Ergicho, B.; Erke, M.; Mengistu, S. and Bedane,A.; Desta, A.(2004). General Pathology. Jimma University, Gondar University Haramaya University, Dedub University.