Flashcards in Neoplasia 1 Deck (19):
CELLS ARE UNRESPONSIVE TO NORMAL GROWTH CONTROLS.
They are able to expand outwith their normal anatomical boundaries; there is increased dispersal around the body.
No differentiation of cells
Tissue is chaotically arranged, but is IN AN APPROPRIATE SITE.
Tissue is chaotically arranged, in an ABNORMAL site.
eg. Dermoid- normal mature haired skin is seen on the cornea of the eye.
The skin has not properly differentiated to it's final form (corneal epithelium) -> irritational conjunctivitis.
ARE LUMPS ALWAYS TUMOURS?
NO. They could be abscesses, and multiple lumps are not always caused by the same thing.
eg. 2 enlarged adrenal glands- one enlarged due to benign nodular hyperplasia (normal part of aging), the other is red and swollen- it may be aplastic.
ARE TUMOURS ALWAYS LUMPS?
NO! Sometimes, primary lesions can be skin ulcerations etc, then secondary neoplasia/metastasis can be seen elsewhere in the body. eg. nodules in the liver.
CHANGES WHICH MAY PRECEDE NEOPLASIA
Preneoplastic changes are reversible, arise in response to physiologic demands, injury or irritation and will REGRESS if the inciting factor is removed.
They are not always pathogenic.
Increased NUMBER of cells.
eg. Gingival hyperplasia. Gum overgrowth affects 30% of boxers over 5 years. Great Dane/Dobermann also.
Not neoplastic but can cause functional problems- bleeding, pain on eating, regrowth on removal.
Cyclosporin and phenytoin can induce this hyperplasia.
eg. Sebaceous hyperplasia. Dome shaped/papillated masses usually seen on head. Non neoplastic; no evidence of cellular invasion of deeper tissues (on histology), sebaceous glands are hyperplastic.
Can become neoplastic- GLANDS LOST, TISSUE BECOMES MORE JUMBLED, INVASION OF UNDERLYING TISSUE.
Increased SIZE of cells.
One type of differentiated cell changes to another.
This is a PRECEDING FACTOR for neoplasia.
Cells lose polarity and thus become 'mixed up' and disarranged.
Can be benign or malignant.
Even benign enlargement (most common cause of prostatic enlargement in older intact male dogs) can cause functional problems.
Enlarged prostate pushes up on colon, restricting passage of faeces.
-May see blood in urine.
VETERINARY TUMOUR GROUPINGS
1. MESENCHYMAL (mesoderm)
-Connective tissue, fat, cartilage.
-Endothelium and related tissue.
-Haematpoietic and lymphoid tissue (bone marrow, spleen/liver in sick animal)
2. EPITHELIAL (endoderm/mesoderm/ectoderm)
-Ectoderm- covering epithelium (eg. skin)
-Mesoderm- solid organs (eg. renal tubules, hepatocytes)
-Endoderm- lining epithelium (eg. GI mucosa)
3. NERVOUS TISSUE- CNS and PNS
Both types of cell can form tumours; tumours can be mixed.
4. MIXED- Divergent differentiation of monoclonal cells (eg. mammary gland- often see cartilage/bone, ovary, testis)
5. UNDIFFERENTIATED- poor prognosis.
eg. a tumour of adipocytes from fat will be called a lipoma if it is benign, or a liposarcoma if it is malignant.
eg. a tumour of skin squamous epithelial cells will be called a squamous papilloma if it is benign, or a squamous cell carcinoma if it is malignant.
BENIGN VS MALIGNANT
There are FOUR important features that allow us to determine between benign and malignant:
1. DIFFERENTIATION AND ANAPLASIA
2. RATE OF GROWTH
3. LOCAL INVASION
4. METASTASIS- spread to distant sites.
BENIGN TUMOUR CHARACTERISTICS
1.DIFFERENTIATION- well differentiated with recognisable structure.
2. RATE OF GROWTH- slow, progressive expansion with mitotic figures rarely being seen.
3. LOCAL INVASION- there is no true invasion, although expansile growth is seen. Tumours are often encapsulated in a fibrous capsule.
4. METASTASIS- no metastasis is seen.
MALIGNANT TUMOUR CHARACTERISTICS
1. DIFFERENTIATION- poorly differentiated, lack definition, structure is often atypical.
2. RATE OF GROWTH- slow to rapid, but is ERRATIC with MITOTIC FIGURES seen- abnormal, asymmetrical.
3. LOCAL INVASION- is seen. Infiltrative growth.
4. METASTASIS- is frequently seen.
Malignant tumours will cause death if untreated.