viva questions Flashcards
(15 cards)
what is osteosarcoma?
osteosarcoma is a primary bone tumour affecting metaphysis of the long bones like distal femur ( most common) , proximal tibia and proximal humerus.
it is characterised by production of immature bone ( osteoid) by tumour cells.
what are the common sites for osteosarcoma?
distal femur ( M.c) followed by proximal tibia , proximal humerus.
what is the typical age group of affected by osteosarcoma?
bimodal age group distribution:-
1) children and adolescents(10-25 years)
2) elderly ( > 40years):- secondary osteosarcoma( associated Paget’s disease , radiation, etc)
what are the classic radiographic features of osteosarcoma?
MAC Lamellar
1)mixed lytic and sclerotic lesion
2) aggressive periosteal reaction ( codman’s traingle, sunburst pattern)
3) Codman’s triangle:-elevation of the periosteum forming a triangular appearance.
4) lamellate( onion -skin) reaction:- Less common, seen in aggressive lesions.
how to differentiate osteosarcoma from Ewing’s sarcoma?
osteosarcoma:-
1) age gp- 10-25 years
2) location:-metaphysics
3) matrix mineralisation - present
4) soft tissue involvement :- common
5) periosteal reaction:- sunburst , cowman’s triangle
Ewing’s sarcoma:-
1)age group:- 5-20 years
2) location:- diaphysis
3)matrix mineralisation:- absent
4) soft tissue involvement:- common
5) periosteal reaction:-onion skin( lamellated pattern) due to repetitive periosteal lifting.
what are the characteristic MRI findings of osteosarcoma?
LOW T1, HIGH T2 signal intensity.
HETEROGENOUS POST contrast enhancement
SOFT TISSUE EXTENSION with peritumoral edema
SKIP LESIONS( satellite nodules in bone marrow)
how does osteosarcoma appear on a ct scan ?
better visualisation odf destruction and mineralised matrix.
soft tissue involvement
calcification within the timor.
what is the role of pet-ct in osteosarcoma ?
1) detects distant mets( esp lungs)
2) assesses metabolic activity of the tumour.
3) monitors to chemotherapy.
how do you stage osteosarcoma?
enneking staging system( for bone tumour)
stageI:-low-grade, no mets
stageII:-high grade, no mets
stageIII:-metastatic disease.
AJCC TNM staging is also used.
what is the most common site for metastases in osteosarcoma?
LUNGS( most common)
BONE( Second most common)
how do lung mets look like on a chest X-ray and ct scan?
multiple round “ cannon ball” opacities.
Ct scan :- well defined nodules. sometimes calcified.
differential diagnosis for aggressive bone lesion in a young patient?
ECOOL
E:- Ewing’s sarcoma
C:- chondrosarcoma ( in older patient)
O:-osteomyelitis
O:-osteosarcoma
L:-langerhans cell histiocytosi
what is the difference between conventional osteosarcoma and parosteal osteosarcoma?
CONVENTIONAL OSTEOSARCOMA
location:- intramedullary
growth:- aggressive, destructive
prognosis:- poorer
periosteal reaction:- sunburst, codman’s triangle.
PAROSTEAL OSTEOSARCOMA
location:-surface of the bone
growth :-slow growing
prognosis:-better
periosteal reaction:-thick, lobulated
what is the imaging features of telangiectatic osteosarcoma?
LYTIC LESION with fluid -fluid levels on MRI( due to blood -filled spaces)
MINIMAL MATRIX mineralisation
HIGHLY AGGRESSIVE with cortical destruction.
what is the significance of tutor necrosis percentage on imaging?
> 90% :- necrosi post -chemotherapy - good prognosis
<90% necrosis:- worse prognosis, poor response
