Bone Formation and Bone Tumors

Question 1

osteoblasts derive from

Answer 1

mesenchymal cells

Question 2

osteoclasts are most like

Answer 2

macrophages–> can form multinucleated cells

Question 3

stimulated by PTH

Answer 3

osteoclasts

Question 4

cartilage replaced by what bone intitially in endochondral ossification

Answer 4

woven bone–> later replaced by lamellar bone, which is stronger

Question 5

what two types of bone are made by membranous ossification

Answer 5

bones of calvarium and facila bones–> woven bone made directly w/o cartilage; also later replaced to lamellar bone

Question 6

defect in achondroplasia

Answer 6

FGFR3–> contsitutively active which inhibits chondrocyte proliferation = short limbs due to early epiphyseal plate closure

Question 7

pattern of inheritance in achondroplasia

Answer 7

autosomal dominant–> homozygotes for the gene are not viable!

Question 8

what can increase risk of achondroplasia

Answer 8

advanced paternal age–> 85% are sporadic mutations

Question 9

MCC benign bone tumor

Answer 9

osteochondroma

Question 10

age range of osteochondroma and characteristic finding

Answer 10

males under 25–> exostosis with cartilaginous cap

*is a type of hamartoma (overgrowth of otherwise normal tissue)

Question 11

benign bone tumor affecting older people. characteristic lesion and where

Answer 11

osteoclastoma (giant cell tumor)–> “soap bubble” appearance on x-ray
*usually around the knee

Question 12

MC bone primary tumor in children

Answer 12

osteosarcoma

Question 13

characteristic age, sex, and 2 lesion seen in osteosarcoma. where?

Answer 13

males under 20; Codman’s triangle or sunburst pattern on x-ray, commonly in metaphysis of dital femur or proximal tibia (knee)

*presents as painful knee; ass. w/ hx of radiation, familial RB. hx of bone infarct

Question 14

bone tumor affects boys under 15

Answer 14

Ewing’s sarcoma

Question 15

translocation of Ewings

Answer 15

t(11,22)

Question 16

Ewing’s commonly appears in what region of what 4 bones

Answer 16

diaphysis of:

1. long bones
2. pelvis
3. scapula
4. ribs

Question 17

characteristic x-ray lesion for Ewings

Answer 17

“onion-skin” lesion

*anaplastic small blue cell malignant tumor; highly aggrssive with early mets, but responsive to chemo

Question 18

malignant bone tumor affecting oldr men

Answer 18

chondrosarcoma

*occurs in diapysis of pelvis, spine, scapula, humerus, tibia or femur

Question 19

5 most likely primary CA to met to bone

Answer 19

1. Prostate
2. Renal cell carcinoma
3. Testes/thyroid
4. Lung
5. Breast

*note the urinary system involvement

Question 20

met producing lytic lesions in bone

Answer 20

lung

Question 21

met producing blastic lesion in bone

Answer 21

prostate

Question 22

PTH at intermittent levels does what

Answer 22

anabolic effect on bone by stimulating osteoclasts and osteoblasts

Question 23

PTH at chronic high levels (hyperparathyroidism)

Answer 23

catabolic effects–> osteitis fibrosa cystica (aka von Recklinghausen disease of bone); is due to excess stimulation of osteoclasts