Classification Of CANCER

Neoplastic tumours classified according to behaviour of tumour(benign or malignant) anatomic site, histologic analysis (grading) and extent of disease(staging).

Anatomic Site Classification            
In this anatomic classification of tumours, the tumour is identified by the tissue origin, the anatomic site and the behaviour of the tumour.i.e benign or malignant.  Carcinoma originates from embryonical ectoderm(skin or glands) and endoderm (mucous membrane linings of the respiratory tract, GI tract and Genitourinary tract). Sarcoma originates from embryonal mesoderm(connective tissue, muscle, bone and fat). Symphomas and leukaemias originate from the hematopoietic system.


Histologic Analytic Classification
The histologic grading of tumours, the appearance of the cells and the degree of differentiation are evaluated. For many tumours, four grades are used;

Grade I              Cells differs slightly from normal cells( mils displasia) and are well differentiated


Grade II             Cells are more abnormal(moderate displasia) and moderately differentiated

Grade III            Cells are very abnormal(severe dysplasia) and poorly differentiated

Grade IV            Cells are immature and primitive(anaplaxia) and undifferentiated, cell of  
                             origin  difficult to determine
Extent of Disease Classification
The extent of disease classification is often called "staging". The clinical staging classification determines the extent of disease process of cancer by stages:

Stage 0 :  Cancer in Situ. It is defined as a neoplasm of epithelial tissue that remains confined to the site of origin

Stage I :     Tumour linked to the tissue of origin, localized tumour growth 

Stage II :    Limited local spread

Stage III :   Extensive local spread

Stage IV :   Metastasis

This type of classification is used as a basis for staging in cancer of cervix and Hodgkin's disease. The TNM classification system represents the standardization of the clinical staging of cancer. It is used to determine the extent of disease process of cancer according to three parameters. Tumour Size(T), degree of regional spread to the lymph nodes(N) and absence of Metastasis()


             TNM STAGING CLASSIFICATION SYSTEM

TUMOUR

T0                                     No evidence of primary tumour

Ts                                     Carsinoma in Situ

T1, T2, T3, T4                Ascending degrees of tumour size and involvement

NODES

N0                                  No evidence of disease in lymph node

N1a, N2a                      Disease found in regional lymph nodes, metastasis not suspected

Nx                                  Regional lymph nodes cannot be assessed clinically

METASTASIS

M0                                No evidence of distant metastasis

M1, M2, M3                 Asscending degrees of metastatic involvement of the host, including distant nodes