Introduction |
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Introduction:
Some of the mechanisms that aid malignant cells to invade are:
-
decreased cell-cell adhesion: malignant
cells have altered cell membranes and altered surface charge and are
less cohesive than normal. Epithelial cells have reduced ability to
form tight junctions.
-
decreased numbers of receptors which bind cells to components of the
basement membrane and extracellular matrix
-
secretion of enzymes: tumour cells
can secrete proteolytic enzymes which degrade components of basement
membranes and extracellular matrix
-
increased motility: malignant cells
are capable of amoeboid motion
Factors which enable classification of tumours as benign or malignant
include:
Cellular morphology – if greater
than 3 nuclear criteria of malignancy are present, it is likely that the
tumour is malignant
Tumour/cellular behaviour – evidence
of local tissue invasion and/or metastatsis – most reliable indicators
of malignancy.
Dermal carcinoma which is invading muscle fibres (x40).
There are three major mechanisms by which malignant neoplasms metastasise:
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