A major LIFE THREATENING DISEASE "CANCER"

NEOPLASIA-

The term ‘Neoplasia’ means- " New Growth"

the new growth produced is called ‘neoplasm’ or ‘tumour’.

However, all ‘new growths’ are not neoplasms since examples

of new growth of tissues and cells also exist in the processes

of embryogenesis, regeneration and repair, hyperplasia and

hormonal stimulation. 

The proliferation and maturation of cells in normal adults is controlled. 

Thus, normally some cells 

proliferate throughout life (labile cells), some have limited proliferation (stable cells), while others 

do not replicate(permanent cells).

On the other hand, neoplastic cells lose control and regulation of replication and form an abnormal mass of tissue.

Therefore, satisfactory definition of a neoplasm or tumour

is ‘a mass of tissue formed as a result of abnormal, excessive,

uncoordinated, autonomous and purposeless proliferation of

cells even after cessation of stimulus for growth which caused

it’. 

The branch of science dealing with the study of neoplasms

or tumours is called Oncology (oncos=tumour, logos=study).

Neoplasms may be

 ‘benign’ when they are slow-growing and localised without causing much difficulty to the host, or

‘malignant’ when they proliferate rapidly, spread throughout

the body and may eventually cause death of the host.

The common term used for all malignant tumours is CANCER.

Hippocrates (460-370 bc) coined the term karkinos for cancer

of the breast.

The word ‘cancer’ means crab, thus reflecting the true character of cancer since ‘it sticks to the part stubbornly like a crab’.

All tumours, benign as well as malignant, have 2 basic components-

”” ‘Parenchyma’ comprised by proliferating tumour cells;

parenchyma determines the nature and evolution of the

tumour.

”” ‘Supportive stroma’ composed of fibrous connective tissue and blood vessels; it provides the framework on which the

parenchymal tumour cells grow.

The tumours derive their nomenclature on the basis of the parenchymal component comprising them. 

The suffix ‘-oma’ is added to denote benign tumours. 

Malignant tumours of epithelial origin are called carcinomas, while 

Malignant mesenchymal tumours are named sarcomas (sarcos = fleshy). 

However, some cancers are composed of highly undifferentiated cells and are referred to as undifferentiated malignant tumours.

Although, this broad generalisation regarding nomenclature

of tumours usually holds true in majority of instances,

some examples contrary to this concept are:

•  melanoma for carcinoma of the melanocytes,
•  hepatoma for carcinoma of the hepatocytes, 
• lymphoma for malignant tumour of the lymphoid tissue, seminoma for malignant tumour of the testis.
• Leukaemia is the term used for cancer of blood forming cells

CHARACTERISTICS OF TUMOURS

Majority of neoplasms can be categorised into benign and

malignant on the basis of certain clinical features, biologic

behaviour and morphological characteristics.

 However, there are exceptions— a small proportion of tumours have some features suggesting innocent growth while other features point towards a more ominous behaviour. Therefore, it must be

borne in mind that based characteristics of neoplasms, there is

a wide variation in the degree of deviation from the normal in all the tumours. 

The characteristics of tumours are described under the following headings:

I. Rate of growth

II. Cancer phenotype and stem cells

III. Clinical and gross features

IV. Microscopic features

V. Spread of tumours

    a. Local invasion or direct spread

    b. Metastasis or distant spread

ŒŒ Neoplasms are categorised into Benign and Malignant on

the basis of certain clinical and morphologic features.

ŒŒ 

The tumour cells generally proliferate more rapidly

than the normal cells; benign tumours grow slowly and

malignant tumours rapidly. 

Tumour Enlargement depends upon -

1. rate of cell production, 
2. growth fraction and
3.  rate ofcell loss and
4.  degree of differentiation of the tumour

Evidence suggests that cancer cells originate by

clonal proliferation of a single progeny of stem cells

(monoclonality).

ŒŒ 

Clinically, Benign tumours are generally slow growing

and may remain asymptomatic while

 Malignant tumours grow rapidly and may spread locally or to distant sites.

ŒŒ 

Grossly, Benign tumours are generally encapsulated or

well-circumscribed, while malignant tumours are usually

irregular in shape, poorly-circumscribed and extend into

the adjacent tissues.

ŒŒ Microscopic features of tumours are more important for

recognising and classifying the tumours. These include-

1. Microscopic pattern of tumour cells,
2. Histomorphology of neoplastic cells, 
3. Tumour angiogenesis,
4. Stromal reaction.

ŒŒ The neoplastic cells are characterised by morphologic and

functional alterations, the most significant of which are

‘differentiation’ and ‘anaplasia’.

 Differentiation is defined as the extent of morphological

and functional resemblance of parenchymal tumour cells to corresponding normal cells.

 Anaplasia is lack of differentiation and is a characteristic

feature of most malignant tumours.

ŒŒ Important features of ANAPLASIA are:- 

1. Loss of polarity,
2. Pleomorphism, 
3. Increased N:C ratio,
4. Hyperchromatism,
5. Prominent nucleoli, 
6. Abnormal mitotic figures, 
7. Qualitative or quantitative cytoplasmic changes, 
8. Chromosomal abnormalities.                                                                                                                                                     Stromal features of significance in tumours are-Angiogenesis,                                                                              Collagenous stroma (desmoplasia)                                        Inflammatory stromal reaction by the host.