Principles of Neoplasia: Definition, Epidemiology

Principles of Neoplasia

DEFINITION

In neoplasia, an abnormal cell or tissue grows more rapidly than normal cells or tissue; it does so by acquiring multiple genetic changes over time and by continuing to grow after the stimuli that initiated the new growth have been removed.

EPIDEMIOLOGY

Cancer is the second leading cause of death in the United States. In 2015, the esti-mated number of new cancers diagnosed was 1,658,370, and the estimated number of deaths from cancer was 589,430.

In men, the sites with the highest new cancer rates are (in order of decreasingfrequency):

·            Prostate

·            Lung and bronchus

·            Colon and rectum

These same sites have the highest mortality rate, although lung and bronchus can-cers more commonly cause death than prostate cancer.

In women, the sites with the highest new cancer rates are (in order of decreasingfrequency):

·            Breast

·            Lung and bronchus

·            Colon and rectum

These same sites have the highest mortality rate, although lung and bronchus can-cers more commonly cause death than breast cancer.

In children, the most common cancers are acute lymphocytic leukemia, CNS malig-nancy, neuroblastoma, and non-Hodgkin lymphoma.

Predisposition to cancer involves many factors. Geographic and racial factors canbe important:

·            Stomach cancer is much more prevalent in Japan than in the United States.

·            Breast cancer is much more prevalent in the United States than in Japan.

·            Liver hepatoma is much more prevalent in Asia than in the United States.

·            Prostate cancer is more prevalent in African Americans than in Caucasians.

Heredity predisposition can be seen in many cancers, including familial retinoblas-toma, multiple endocrine neoplasia, and familial polyposis coli.

Acquired preneoplastic disorders also affect cancer incidence, with examples includ-ing cervical dysplasia (characterized by changes in cell size and shape), endometrial hyperplasia, cirrhosis, inflammatory bowel disease, and chronic atrophic gastritis.