scr - os & histopathology - tumours

Question 1

odontogenic tumours

Answer 1

majority asymptomatic often discovered due to:
- non eruption of teeth
- late stage bony expansion
- incidental finding
pain is usually due to pathological # or 2ndary infection

Question 2

3 groups of odontogenic tumour

Answer 2

1. epithelial -> ameloblastoma / adenomatoid odontogenic tumour / calcifying epithelial odontogenic tumour
2. mesenchymal -> odontogenic myxoma
3. mixed (both of above) -> odontoma

Question 3

mixed tumours specifically

Answer 3

can have enamel / dentine formation due to concept of induction
1st formed dentine from odontoblasts which are mesenchymal in origin
ameloblasts mature & form enamel only when dentine starts getting laid down so present of dentine crucial for induction for maturation of ameloblast formation of enamel

Question 4

odontogenic sources of epithelium

Answer 4

rests of malassez - from hertwig’s epithelial root sheath
rests of serres - from dental lamina
reduced enamel epithelium - from enamel organ

Question 5

ameloblastoma

Answer 5

benign epithelial tumour
locally destructive but slow growing & typically painless
1% of OMFS tumours
4th-6th decades most common
80% posterior mandible
M>F

Question 6

radiographic appearance of ameloblastoma

Answer 6

well defined bone surrounding pathology
well defined corticated margins
scalloped & multicystic
thick curved septa i.e. soap bubble appearance
primarily radiolucent

Question 7

adjacent structures to ameloblastoma

Answer 7

1. displacement; characteristic expansion pattern (expands in all directions fairly equally)
2. thinning of bony cortices
3. ‘knife edge’ external root resorption

Question 8

histopathological criteria of ameloblastoma

Answer 8

can be:
follicular
plexiform
desmoplastic

Question 9

plexiform form

Answer 9

shows fibrous tissue / stellate reticulum like tissue / ameloblast like cells
no CT capsule
so cells can grow & infiltrate into jaw bone & is one of the main reasons for high recurrence rate

Question 10

follicular form

Answer 10

islands bordered by cells that resemble ameloblasts
tissue in middle of follicles is loose resembling stellate reticulum of tooth germ & can sometimes have cystic changes in follicle

Question 11

management of ameloblastoma

Answer 11

1. surgical resection with margin
2. recurrence relatively common ~ 15%
3. risk of malignant transformation <1% (ameloblastic carcinoma)

Question 12

how would benign tumour appear in ultrasound (4)

Answer 12

well defined
encapsulated
peripheral vascularity
no lymphadenopathy

Question 13

options for differential diagnosis for multilocular radiolucency in mandible

Answer 13

OKC
ameloblastoma
ameloblastic fibroma
odontogenic myxoma
odontogenic fibroma

Question 14

follicular histopathology

Answer 14

tumour cells in follicular pattern
resemble enamel organ in developing tooth with a central mass resembling the stellate reticulum
surrounded by ameloblast like cells that display the typical reversed polarity, the nuclei are located away from the basement membrane opposite to what is usual

Question 15

changes in the stellate area within the follicle

Answer 15

cystic breakdown - looks like large white spaces
squamous metaplasia
granular cell changes

Question 16

plexiform histopathology

Answer 16

neoplastic epithelium arranged as a network of strands and irregular masses displaying the same cell layers as the follicular pattern with reversed polarity obvious
cyst degeneration in this type is mainly due to stromal degeneration

Question 17

adenomatoid odontogenic tumour

Answer 17

benign epithelial tumour
3% of odontogenic tumours
most common 2nd decade
F>M
anterior maxilla

Question 18

key about AOT

Answer 18

75% associated with u/e tooth, commonly maxillary canine

Question 19

radiographic criteria of AOT

Answer 19

unilocular radiolucency
majority have internal calcification / radiopacities which increase as tumour matures
margins well defined & corticated
may displace adjacent structures but external root resorption rare
very similar to dentigerous cyst

Question 20

difference between AOT & dentigerous cyst

Answer 20

AOT has
1. thicker cortical margins
2. attaches further down root (cyst attaches at CEJ)

Question 21

histopathological criteria of AOT

Answer 21

epithelial in origin
arranged in duct like structures (big hole) described as rosette appearance
distinctive with patchy calcification
well developed fibrous tissue capsule surrounding cells so removal of tumour straightforward surgically & recurrence rate is LOW

Question 22

calcifying epithelial odontogenic tumour

Answer 22

benign epithelial tumour
1% odontogenic tumours
most common 5th decade
M>F
posterior mandible most common
slow growing but can become large
1 in 2 associated with u/e tooth

Question 23

radiographic criteria of CEOT

Answer 23

variable presentation
uni or multi locular
well or poorly defined margins
internal septa - poor / fine / none

Question 24

odontogenic myxoma

Answer 24

mesenchymal benign tumour
3-6% of odontogenic tumours
most common in 3rd decade
F = M
Mandible > maxilla

Question 25

radiographic criteria of odontogenic myxoma

Answer 25

well defined radiolucency +/- thin corticated margin small lesions = unilocular large lesions = multilocular soap bubble appearance of septa slow growth along bone before causing buccolingual expansion scallops between teeth but larger lesions may cause displacement; external root resorption rare

Question 26

histopathological criteria of odontogenic myxoma

Answer 26

loose myxoid tissue with stellate cells may contain islands of inactive odontogenic epithelium no capsule = locally invasive

Question 27

odontogenic myxoma management

Answer 27

curettage / resection depending on size high recurrence ~ 25% follow up important lower recurrence rate if unilocular

Question 28

odontoma

Answer 28

benign mixed tumour technically a hamartoma malformation of dental tissue 1/5 - 2/3 of all odontogenic tumours most common 2nd decade F = M

Question 29

odontoma similarities to teeth

Answer 29

mature to certain stage can be associated with other odontogenic lesions e.g. dentigerous cyst surrounded by dental follicle lie above IAN canal

Question 30

2 types of odontoma

Answer 30

complex -> disorganised mass of dental tissue, more common posterior body of mandible compound -> ordered dental structures, may appear as multiple mini teeth, more common anterior maxilla

Question 31

radiographic criteria of odontoma

Answer 31

well defined clump of radiopaque material

Question 32

histopathological criteria of odontoma

Answer 32

both from mesenchymal & epithelial tissue enamel is inorganic so is dissolved during process of slide development; may not show on slide dependent on level of calcification

Question 33

ossifying fibroma clinical criteria

Answer 33

slow growing wide age range mainly mandible similar to fibrous dysplasia but has capsule which is reflected in radiolucent line surrounding mass whereas dysplasia blends into the bone

Question 34

histopathological criteria of ossifying fibroma

Answer 34

cellular fibrous tissue immature bone acellular calcifications

Question 35

fibrous dysplasia

Answer 35

slow growing asymptomatic bony swelling due to bone being replaced by fibrous tissue active u20yrs of age can be single or multiple bone maxilla > mandible can be syndromic - albright's syndrome (melanin pigment & early puberty)

Question 36

radiographic criteria of fibrous dysplasia

Answer 36

margins often blend into adjacent bone bone maintains approximate shape initially becomes more radiopaque as lesion matures can have variable appearances i.e. cotton wool / amorphous

Question 37

histopathological criteria of fibrous dysplasia

Answer 37

fibro osseous fibrous replacement of bone no capsule separating it from normal bone bone remodels and increases in density

Question 38

rarefying osteitis

Answer 38

localised bone loss in response to inflammation always occurring 2ndary to another form of pathology if at apex of tooth consider apical periodontitis / PA granuloma / PA abscess

Question 39

sclerosing osteitis

Answer 39

localised increase in bone density in response to low grade inflammation most common around apex of tooth with necrotic pulp PA radiopacity often poorly defined may eventually lead to external root resorption if chronic

Question 40

osteosarcoma

Answer 40

malignancy of bone normally in 30s if older generally due to paget's mandible > maxilla recurrence, local destruction & metastases

Question 41

paget's disease

Answer 41

usually >40ys M > F aetiology unknown serum biochemistry shows raised alkaline phosphatase disease of disturbed bone turnover -> deposition & resorption occur at the same time so bone becomes soft & deformed then calcifies in deformed shape

Question 42

dental changes with paget's

Answer 42

loss of lamina dura hypercementosis migration (due to bone enlargement)

Question 43

histology of paget's

Answer 43

reversal lines - indicate change in turnover which can be very darkly stained will burn out itself osteoclastic & osteoblastic activity

Question 44

tx of paget's pt

Answer 44

xla of teeth can be difficult due to hypercementosis / pathological # of mandible / affected bone tends to develop osteosarcoma dense bone harder to LA MRONJ risk as on anti resorptives osteosclerotic stage = less vascular so little bleeding so increased risk of dry socket / MRONJ osteolytic stage = more vascular so lots of bleeding