TUMOR
ROLL NO 91 TO 96
INTRODUCTION
The term ‘neoplasia’ means new growth; the new growth produced is
called ‘neoplasm’ or ‘tumour’ .
The prolife ration and maturation of cells in normal adults is
controlled. Thus, normally some cells proliferate throughout life
(labile cells), some have limited proli feration (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
DEFINATION
‘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.
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.
CLASSIFICATION OF TUMOR
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.
Catagories of tumor
1. Mixed tumours When two types of tumours are combined in the
same tumour, it is called a mixed tumour. example: i)
Adenosquamous carcinoma
2. Teratomas These tumours are made up of a mixture of various
tissue types arising from totipotent cells derived from the three germ
cell layers—ectoderm, mesoderm and endoderm. Most common sites
for teratomas are ovaries and testis
3. Blastomas (Embryomas) Blastomas or embryomas are a group
of malignant tumours which arise from embryonal or partially
differentiated cells which would normally form blastema of the organs
and tissue during embryogenesis.
4. Hamartoma is benign tumour which is made of mature but
disorganised cells of tissues indigenous to the particular organ
5. Choristoma is the name given to the ectopic islands of normal
tissue.
CHARACTERISTICS OF TUMOR
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
1. RATE OF GROWTH
The tumour cells generally proliferate more rapidly than the normal
cells. In general, benign tumours grow slowly and malignant tumours
rapidly.
The rate at which the tumour enlarges depends upon 2 main factors:
1. Rate of cell production, growth fraction and rate of cell loss
2. Degree of differentiation of the tumour
2.CANCER PHENOTYPE
Normally growing cells in an organ are related to the neighbouring cells
—they grow under normal growth controls, perform their assigned
function and there is a balance between the rate of cell proliferation
cancer cells exhibit anti-social behaviour
i) Cancer cells disobey the growth controlling signals in the body and
thus proliferate rapidly.
ii) Cancer cells escape death signals and achieve immortality.
iii) Imbalance between cell proliferation and cell death in cancer causes
excessive growth.
iv) Cancer cells lose properties of differentiation and thus perform little
or no function.
v) Due to loss of growth controls, cancer cells are genetically unstable
and develop newer mutations.
vi) Cancer cells overrun their neighbouring tissue and invade
III. CLINICAL AND GROSS FEATURES
Clinically, benign tumours are generally slow growing, and
depending upon the location, may remain asymptomatic
malignant tumours grow rapidly, may ulcerate on the surface, invade
locally into deeper tissues, may spread to distant sites (metastasis),
and also produce systemic features such as weight loss, anorexia and
anaemia.
Gross appearance
Benign tumours are generally spherical or ovoid in shape. They are
encapsulated or well-circumscribed, freely movable, more often firm
and uniform,
Malignant tumours, on the other hand, are usually irregular in shape,
poorly-circumscribed and extend into the adjacent tissues. Secondary
changes like haemor rhage, infarction and ulceration are seen more
often.
IV. MICROSCOPIC FEATURES
These features appreciated in histologic sections are as under:
1. Microscopic pattern
2. Histomorphology of neoplastic cells (differentiation and anaplasia)
3. Tumour angio genesis and stroma
4. Inflammatory reaction.
V. SPREAD OF TUMOURS
LOCAL INVATION
BENIGN TUMOURS Most benign tumours form encapsula ted or
circum scribed masses that expand and push aside the surrounding
normal tissues without actually invading, infiltrating or metastasising.
MALIGNANT TUMOURS Malignant tumours also enlarge by
expansion and some well-differentiated tumours may be partially
encapsulated as well
METASTASIS (DISTANT SPREAD)
Metastasis (meta = transformation, stasis = residence) is defined as
spread of tumour by invasion in such a way that discontinuous
secondary tumour mass/masses are formed at the site of lodgement.
Benign tumours do not metastasise while all the malignant tumours
can metastasise, barring a few exceptions like gliomas of the central
nervous system
Routes of Metastasis
Cancers may spread to distant sites by following pathways:
1. Lymphatic spread
2. Haematogenous spread
3. Spread along body cavities and natural passages
GRADING AND STAGING OF CANCER
‘Grading’ and ‘staging’ are the two systems to predict tumour
behaviour and guide therapy after a malignant tumour is detected.
GRADING
Grading is defined as the gross appearance and microscopic degree
of differentiation of the tumour.
grading is largely based on 2 important histologic features: the
degree of anaplasia, and the rate of growth.
Grade I: Well-differentiated (less than 25% anaplastic cells)
Grade II: Moderately-differentiated (25-50% anaplastic cells)
Grade III: Moderately-differentiated (50-75% anaplastic cells)
Grade IV: Poorly-differentiated or anaplastic (more than 75% anaplastic
cells)
STAGING
The extent of spread of cancers can be assessed by 3 ways— by
clinical examination, by investigations, and by pathologic
examination of the tissue removed. Two important staging systems
currently followed are: TNM staging and AJC staging.
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