Benign Tumour in Organ
Well circumscribed
They grow evenly in all directions, giving a spherical mass
Benign TIssue in Epithelial Surface
Papillary outgrowths growing in the direction of least resistance.
Because of their papillary shape they are called papillomas
Malignant Tumour
Irregular in outline, with indistinct edges.
How to identify malignant tumours
Is there any clinical evidence of invasion or spread to distant sites?
Is there imaging evidence of invasion or spread to distant sites?
ANSWER TO BOTH OR EITHER MAY BE “YES”, BUT
OFTEN ONLY IN ADVANCED TUMOURS
How to accurately and confidently identify malignant tissue
Biopsy and histological examination of a sample of tumour cells or tissue
Benign vs Malignant Tumours
Cellular Pleomorphism
Variation in size and shape of cells in tumour
NUCLEAR PLEOMORPHISM
variation in size and shape of nuclei in tumour cells
NUCLEAR HYPERCHROMATISM
very dark-staining nuclei
due to increased nuclear DNA
HIGH MITOTIC COUNT
increased numbers of cells in mitosis, including abnormal mitotic forms
Cytological characteristics of malignancy
Poor Differentiation Pleomorphism & Abnormal Mitoses High Mitotic Count Nuclear Hyperchromatism High nucleus to Cytoplasm Ratio
Features of dysplastic cells that lead to their abnormal structure
Loss of differentiation Pleomorphism Nuclear hyperchromatism High nucleus/cytoplasm ratio High mitotic activity
Does dysplasia in tumour cells always mean invasive behaviour?
Usually but not always
Carcinoma-in-situ
Epithelium showing the cytological Characteristics of malignancy, but no evidence of invasion
**Non-invasive Dysplasia
What happens to dysplastic cells
Sometimes dysplasia regress but more often turns into invasive malignancy
What happens when a malignant tumour invades the lumen of a lymphatic vessel
Bits of it break off and pass to the lymph nodes draining the area
How do the tumour cells proliferate to replace the whole lymph node
They reach the lymph node and are trapped in the subcapsular sinus where they proliferate to replace the whole node
Blood Stream Spread of Cancer
When a tumour invades the wall of a small vessel, clumps of it break off and pass in the circulation until they meet a vessel too small to let it pass
- Causes tumour embolism
The tumour cells may grow to cause a distant metastasis
Common Sites of Blood-Borne Metastasis
Brain/CSF Lung Liver Adrenals Bone
Where do liver metastases often originate
GI Tract, Pancrease, Breast, Lung/Bronchus, Kidney
Where do bone metastases often originate
Breast Bronchus/Lung Kidney Thyroid Prostate
How can benign tumours cause death/illness
Bleeding - e.g. gut/bladder
Pressure on adjacent vital structures - e.g. Brain
Obstruction - e.g. Brain, bronchus
Hormone secretion - e.g. pituitary adenoma
Conversion to a malignant tumour
