2 Pathlogy of Cancer

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1Pathology of Cancer/RS/SHEK3301-2-2014/15

SHEK 3301- CANCER BIOLOGY

Pathology of Cancer

Pathology

Diagnosis

Prognosis

Identifying features

Methods

Pathology-Branch

Histopathology: microscopic examination of biological tissues to observe the

appearance of diseased cells and tissues in very fine detail.

Cytology: The medical and scientific study of individual cells.

Chemical pathology: analysis of tissues, blood and urine

e.g. to distinguish between benign and malignant cells

Benign are not usually life-threatening and therefore treatments of the two types of growth

are different.




Malignancy is usually characterized by various behavioural features, most notably:

Invasion

The capacity to infiltrate the surrounding tissues and organs.

Metastasis

The ability to proliferate in distant parts of the body, after tumour cells have been

transported by lymph or blood or along body spaces.




Diagnosis

Is it cancer?

What type of cancer? Histogenesis

e.g. to determine the cellular origin of a cancer (histogenesis)

Cancer in an organ can have several origins.

Thus, in lung, smoking generates epithelial cancers whereas mesothelial cancers

result from asbestos exposure.

As treatments are different, the importance of determining histogenesis is clear.

Cancers are described according to their cell of origin and the tissue in which they arise.

Epithelium (Carcinoma)

The type of epithelium is additionally identified.

Glandular epithelium generates an adenocarcinoma. (e.g. prostate adenocarcinoma)

A cancer of squamous epithelium would be a squamous cell carcinoma. (e.g. cervical

squamous cell carcinoma)

Mesenchyme (sarcoma)

Smooth muscle: leiomyosarcoma

Bone: osteosarcoma




Nervous system

Eye: retinoblastoma

Astrocytes: astrocytoma

White blood cells (leukaemia)

Leukaemias are further defined according to the speed with which they develop.

Acute myeloid leukaemia (AML) exhibit rapid onset of symptoms.

Chronic myeloid leukaemia (CML) exhibit slow onset of symptoms.

For historical reasons, some cancers are named after their discoverers:

Burkitt’s lymphoma is a B-lymphocyte cancer

Wilm’s tumour is a renal carcinoma in young children

Kaposi’s sarcoma arises from endhothelial cells of blood vessels.

Identifying features

Cell and tissue architecture.

Differentiation: degree it resembles normal.

Cell structure: nucleus, mitosis, nuclear/cytoplasmic ratio.

Localised (in situ)or invasive (stroma, blood vessels)




In situ or Invasive

An early stage cancer in which the cancerous growth or tumour is still confined to

the site from which it started, and has not spread to surrounding tissue or other

organs in the body.

When cancer in situ involves cells that line the internal organs, or epithelial cells, it is

called carcinoma in situ.

Tumours, on the other hand, which exhibit all the microscopic features of cancers

but do not breach the original basement membrane, are termed in situ (non-

invasive) cancers.

Invasive: Cancer that has spread beyond the layer of tissue in which it developed

and is growing into surrounding, healthy tissues.

The progression begins with a mutation that makes the cell more likely to divide.

The altered cell and its descendants grow and divide too often, a condition

called hyperplasia.

At some point, one of these cells experiences another mutation that further

increases its tendency to divide; this cell's descendants divide excessively and look

abnormal, a condition called dysplasia.




As time passes, one of the cells experiences yet another mutation, causing very

abnormal structure, loss of differentiation, and loss of contact between the cells;

however, it is still confined to the epithelial layer from which it arose, so it is called

a cancer in situ. The in situ cancer may remain contained indefinitely, but additional mutations may

occur that enable it to invade neighbouring tissues and shed cells into the blood or

lymph, the tumour is said to be an invasive cancer (malignant).

The escaped cells may establish new tumours (metastases) at other locations in the

body.

Methods

Staining

Immunohistochemistry: protein

In situ hybridisation: mRNA

Routine H&E staining and special stains play a critical role in tissue-based diagnosis

or research.

By colouring otherwise transparent tissue sections, these stains allow highly trained

pathologists and researchers to view, under a microscope, tissue morphology

(structure) or to look for the presence or prevalence of particular cell types,

structures or even microorganisms such as bacteria.




The term special stains traditionally referred to any staining other than an H&E.

In situ hybridization (ISH) is a powerful technique for localizing specific nucleic acid

targets within fixed tissues and cells, allowing you to obtain temporal and spatial

information about gene expression and genetic loci.

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2 Pathlogy of Cancer