bone tumours Flashcards
what is the composition of bone?
INORGANIC - 65%
calcium hydroxyapatite (10Ca 6PO4 OH2)
is storehouse for 99% of Ca in the body
85% of the phosphorous, 65% Na & Mg
ORGANIC - 35%
– bone cells and protein matrix
– made of the likes of collagen, carbs, water, etc
what are the types of bones? differences?
Cortical / Compact
- long bones
- appendicular skeleton
- 80-90% calcified
Cancellous / Trabecular
- axial skeleton
- 15% calcified
- Cancellous bone is metabolically more active than cortical.
what are osteocytes?
osteoblast like cells which sit in the lacunae in bone
whats the structure of cortical bone?
circumferential lamellae outside
concentric
interstitial
trabecular lamellae
in decreaseing order
Haversian canal - up and down - contains blood vesse;s, nerves, lymph
volkmann canal - side to side
osteobalsts come from?
osteoprogenitor cells
what increases bone resorption?
when RANK-Ligand binds to RANK on the surface of an osteoclast
what is a regulator in bone resorption?
Osteoprotegerin:
competes with RANK for RANK-Ligand
meaning less osteoclast activation/osteoclastogenesis
what is the effect of tumours on bone and how?
- Bone resorption:
production of PTHrp & serum RANKL
these induce osteoclasts hence resorption - Bone formation:
via TGFB, FGF, ET1
Tumours not only induce bone resorption (osteolysis) but can induce new bone formation. Metastatic prostate carcinoma often causes more bone growth than destruction.
What type of bone is found in conditoins eg (Pagets disease of bone, certain stages of flouride treatment, tumours).
how is it different from normal bone?
Woven bone:
lamellar are absent. Collagen fibres are laid down in a disorganized fashion: such as states of high bone turnover
viewed under polarised light
what is required for bone histology?
- Histology requires bone biopsy from the iliac crest
* The sample must be processed and un-decalcified for histomorphometry
- Bone mineralisation is studied using _____
* Histodynamic parameters are obtained from ______
a. osteoid parameters
b. fluorescent tetracycline labelling
for osteoporosis,
what is the aetiology, pathogenesis and which parameters are used to determine osteoporosis
low initial bone mass or accelerated bone loss can reduce bone mass below the fracture threshold
Aetiology – 90% cases due to insufficient Ca intake and post-menopausal oestrogen deficiency
1º - age, post-menopause
2º - drugs, systemic disease
‘High turnover’ OP results from ↑ bone resorption
‘Low turnover’ OP results from ↓ bone formation
most common presentation of osteoporosis ?
Patients commonly present with back pain and Fracture
Fractures; wrist (Colles’), hip (Neck of femur and intertrochanteric) & pelvis may be the first sign of disease > 60% vertebral # are asymptomatic
how would you ivx osteoporosis and what results would you see?
§ Serum calcium, phosphate and ALP (usually NORMAL) § Urinary calcium § Collagen breakdown products ○ Imaging ○ Bone Densitometry
§ T-Score of -1 to -2.5 = osteopaenia
T score lower than -2.5 = osteoporosis
what is osteomalacia? subtypes?
Defective bone mineralisation
2 types effectively:
1. Deficiency of vitamin D
2 Deficiency of PO4
looser zone fractures are associated with?
osteomalacia
list causes of primary and secondary hyperparathyroidism?
1º -
parathyroid adenoma (85-90%)
chief cell hyperplasia
2º -
chronic renal deficiency
vit D deficiency
malabsorption
what does Renal Osteodystrophy entail?
Comprises all the skeletal changes of chronic renal disease
Increased bone resorption (osteitis fibrosa cystica) Osteomalacia Osteosclerosis Growth retardation Osteoporosis
what does the clinical chemistry look like for Renal Osteodystrophy?
High PO4-
High PTH
Low Ca2+
metabolic acidosis
aluminium deposits.
what are the types of pagets?
- Osteolytic
- Osteolytic-osteosclerotic
- Quiescent osteosclerotic
which disease is the following implicated:
autosomal pattern of inheritance with incomplete penetrance (mutation 5q35-qter - sequestosome 1 gene)
Pagets
Parvomyxovirus type particles have been seen on EM in ___ bone
Pagetic bone
when is a bone biopsy warranted?
Suspected osteomalacia
Diagnostic classification of renal osteodystrophy
Osteopaenia in young patients <50y
Osteopaenia associated with abnormal Ca metabolism
Classification of hereditary childhood bone disease
Evaluation of treatment
what is the clinical picture in pagets?
pain
microfractures
nerve compression (incl. Spinal N and cord)
skull changes may put medulla at risk
+/- haemodynamic changes, cardiac failure
Development of sarcoma in area of involvement 1%
