Adaptive changes and neoplasia Flashcards
Aplasia
Failure of a tissue/organ to develop
Hypoplasia
tissue develops but not to its full size
-can range from being mildly hypoplastic to almost complete absence
Atrophy
Decrease in the size of cells / organ after the tissue has reached normal size
the atrophic organ or tissue may be smaller and paler
cells of smaller size
reversible
Examples of Aetiology:
starvation and malabsorption
compression (by a nearby lesion)
immobilisation of limb (disuse) results in atrophy of the muscles
reduced blood supply
loss of nerve supply (denervation)
lack of trophic hormones
chronic inflammation
ageing
Hypertrophy
An increase in the size of an organ due to an increase in size of the individual cells (no increase in cell division)
Physiological:
occurs in response to an increased physiological need e.g. muscles of the heart and limbs in training, or uterus to enable pregnancy
Pathological:
Occurs in response to an increased demand because of organ dysfunction e.g. cardiac hypertrophy due to heart failure
Compensates for the loss of one of a pair of organs or when there is obstruction to outflow from an organs
Driven by abnormal levels of hormones
Other types of pathological hypertrophy
Compensatory hypertrophy:
occurs when one of a paired organs is damaged or lost e.g. the kidneys.
Obstructional hypertrophy:
hollow organs may become thickened around an obstruction eg: intestine, bladder, gall bladder
Hormone mediated hypertrophy:
anabolic steroids produce hypertrophy of muscle
-thyroid hormones have a general hypertrophic effect on tissues increasing protein synthesis within them e.g. older cats with hyperthyroidism also get cardiac hypertrophy
Hyperplasia
an increase in the size of an organ due to an increase in the numbers of cells i.e. increase in cell division (mitoses)
Aetiology:
hormonal stimulation such as prostatic hyperplasia in older dogs
response to irritation
regeneration in response to cell loss or injury
Hyperplasia morphology
Hyperplastic nodules can be seen in a variety of organs in older dogs and cats e.g. thyroid in cats, and spleen and liver of dogs
increase in the numbers of cells, mitotic activity and cellular basophilia (indicates increased RNA and protein synthesis)
the cells are well differentiated and tissue structure is normal
Hyperplasia stops when cause stops
Hyperplastic cells may be more prone to undergo neoplastic change
Metaplasia
transformation of one type of tissue into another
Usually the tissue’s way of trying to protect itself following repeated damage
In connective tissue, the metaplastic change is from fibrous tissue to cartilage and bone in damaged tissue
In epithelial tissue, squamous metaplasia of cuboidal or columnar epithelium is quite common e.g. in bronchi of people who smoke
Dysplasia
Abnormal growth/differentiation within a tissue
the normal arrangement and pattern of the tissue is lost
can be developmental e.g. renal dysplasia in some breeds of dogs predisposes to renal failure early in life
can be due to chronic irritation and trauma
dysplasia can be a precursor to neoplasia
Neoplasia
an uncontrolled, proliferation of abnormal cells
the proliferation continues in the absence of the inciting cause
the neoplastic cells originate from a single cell which has undergone mutation and lost the ability to control its division = clonal expansion
Benign neoplasms
Macroscopically:
often smooth in outline
freely mobile when palpated
little haemorrhage or necrosis
surgical removal often easy
no recurrence if excised
no metastasis
Microscopically:
similar to the tissue of origin = well differentiated
outer capsule often present
there are few or no mitoses
Malignant neoplasms
Macroscopically:
invasive and fixed to adjacent tissue
not encapsulated
complete removal is often difficult
tend to recur at the site of excision
can metastasise
Microscopically:
very variable
can be undifferentiated / anaplastic
the nuclei may be of differing sizes and shapes even multiple producing giant cells
frequent mitoses
Tumour nomenclature
Benign tumours:
Surface epithelia e.g. skin - papilloma
Glandular epithelia - adenoma
Both can be prefixed by the tissue of origin e.g. squamous cell papilloma or thyroid adenoma
Malignant tumours
A malignant tumour of epithelial origin is a carcinoma
Tumours of glandular epithelia are termed adenocarcinomas
The tissue of origin is then added e.g. squamous cell carcinoma or mammary adenocarcinoma
Tumour nomenclature exceptions
Lymphomas – tumours of the lymphoid system. Usually malignant
Melanomas – tumour of melanocytes. Some are benign (melanocytomas), others are malignant (malignant melanomas)
Mast cell tumours (mastocytoma) – tumour of mast cells. These vary in degree of malignancy
Leukaemias – tumours derived from the cells of the bone marrow which circulate in the blood.
Teratomas – a primitive germ cell tumour with elements of ectoderm, endoderm and mesoderm.
Sarcoid – a low grade fibrosarcoma commonly seen in the skin of horses
Routes of tumour metastasis
Local invasion
direct growth into adjacent tissue
spread along natural tissue planes
Lymphatic Spread - carcinomas
draining lymphatic vessels to local node
Vascular Spread – sarcomas
Transcoelomic Spread
seeding the peritoneal or pleural cavities (exfoliation)
