Bone, cartilage, joint pathology

Question 1

Knee joint.

Dx?
Key features?
XR features?

Answer 1

Synovial chondromatosis
Features: Synovial chondromatosis has a well-defined, multinodular architecture, characterized by discrete nodules of hyaline cartilage within subsynovial tissue. The chondrocytes are arranged in small clusters. Matrix usu hyaline but can be myxoid. Can undergo endochondral ossification.
XR: periarticular punctate calcifications

Question 2

Erdheim Chester disease

What is it?
Common genetic mutation
Key histo features
IHC

Answer 2

Rare, clonal histiocytosis with frequent multiorgan involvement
Also known as polyostotic sclerosing histiocytosis
Skeletal involvement in almost all (> 95%) cases, most often in the long bones of the lower extremities

Correlation of clinical features, histology and radiological findings are essential for diagnosis (Blood 2016;127:2672)
Systemic disease with frequent involvement of bone, retroperitoneum (hairy kidney, coated aorta), CNS and lung

BRAF V600E mutation in > 50% of cases

Soft tissue infiltrate of bland appearing histiocytes characterized by abundant foamy (xanthomatous) cytoplasm with surrounding fibrosis
Touton giant cells are frequently present
Associated lymphoplasmacytic infiltrate is sparse
Erdheim-Chester disease may be a component of mixed histiocytosis with Langerhans cell histiocytosis or Rosai-Dorfman disease

Question 3

osteoid osteoma vs osteoblastoma

distinguishing clinical and radiological features?

Answer 3

NB: RFA = radiofrequency ablation

Question 4

gene rearrangements in osteoid ostoma and osteoblastoma

Answer 4

FOS (and less so FOS-B) gene rearrangements.
FOS gene rearrangements also found in epithelioid haemangioms

Question 5

osteosarcoma

RF for primary vs secondary osteosarcoma

Answer 5

Question 6

Anatomically, how can osteosarcoma be described and which are high vs low grade

Answer 6

Question 7

hereditary condition a/w multiple osteochondromas?
Mode of inheritance?

Answer 7

Multiple hereditary exostosis.
Autosomal dominant.

Question 8

multiple endchondromas, syndromic association?

Answer 8

Ollier’s syndrome (not inherited)

Question 9

Maxillary incidental lesion:
Dx?
Essential dx features?

Ddx:

Answer 9

Osteoma
Essential: bone tumour with compatible imaging; tumour arises on the surface of bone or within the medullary cavity; tumour composed of lamellar/cortical-type bone.

osteoblastoma/osteoid osteoma; osteosarcoma

Question 10

Gene rearrangements in osteoid osteoma; osteoblastoma?

Answer 10

FOS gene rearrangement (not necessary for diagnosis) may be found in osteoid osteoma, but it can also be found in osteoblastomas and epithelioid haemangiomas

Question 11

osteoid osteoma vs osteoblastoma?

Answer 11

Question 12

describe an approach to bone and cartilage forming tumours? (hint: 4 x4)

Answer 12

Question 13

How could you distinguish LG central osteosarcoma from fibrous dysplasia?

Answer 13

FISH for CDK4 or MDM2 amplification

Question 14

Gene rearrangement in ABC?

Answer 14

Translocation involving the USP6 gene

Question 15

syndromes associated with increased risk of chondrosarcoma

Answer 15

Ollier disease and Maffucci syndrome

Question 16

what is the size cut-off between osteochondroma and chondrosarcoma?

Answer 16

2cm

Question 17

syndromes associated with:
Enchondromas
Osteochondromas

Answer 17

Enchondromas: Ollier’s disease and maffucci syndrome
Ollier disease: multiple enchondromas in the appendicular skeleton in an asymmetric manner
Typically in short and long bones of the limbs; epiphyseal tumors can prevent normal bone growth in young patients
Maffucci syndrome
Multiple enchondromas in association with soft tissue and visceral hemangiomas and lymphangiomas

Osteochondroma: Multiple hereditary exostosis (AD) /hereditary multiple osteochondroma syndrome. Multiple osteochondroma syndrome is an AD condition caused by mutation sin EXT1 or EXT2.

Question 18

mesenchymal chondrosarcoma: key features, demographic, location and molecular

Answer 18

Key features:
- primitive/PD round cells
-staghorn vessels
-WD islands hyaline cartilage

Age: 2nd-3rd decade
Location: craniofascial 50%
Molecular: HEY1-NCOA2 rearrangement

Question 19

Enchondromas - key features + location?

Disease/syndromic associations?

Answer 19

Benign hyaline cartilage neoplasm of medullary bone. Most solitary. Lobular, cell poor, hyaline cartilage -> demarcated by zone of reactive bone formation.

Site: Hands and feet (uncommon for ACT).

Nonhereditary Ollier disease and Maffucci syndrome (latter = multiple enchondromas + spindle cell haemangioma).

Question 20

synovium shoulder joint.
Dx?
How to prove?

Answer 20

pseudogout

Weakly anisotropic rhomboid to rod shaped crystals demonstrating positive birefringence under polarized light

Diagnosis requires demonstration of calcium pyrophosphate crystals in synovial fluid or biopsy material

Question 21

chondroblastoma key features and IHC?

Answer 21

skeletally immature, epiphyeal/apophyseal location
ovoid, polygonal cells with grooved nuclei
islands of chondroid matrix
Giant cells
chicken wire calcifications

IHC:
antibody against H3.3B (H3F3B) p.Lys36Met (K36M) shows diffuse nuclear expression in > 96% of the cases

Question 22

genetic mutation in osteoid osteoma and osteoblastoma?

Answer 22

rearrangements of the FOS gene

Question 23

which syndromes are a/w markedly increased risk of chondrosarcomas?

Answer 23

Ollier disease and Maffucci syndrome

Question 24

Subtypes of conventional osteosarcoma ? (7)

Answer 24

Osteoblastic
Giant cell rich
Chondroblastic
Fibroblastic
Telangiectatic
Small cell variant
Epithelioid