Histopathology 2 - Bone tumours

Question 1

What is the preferred investigation for diagnosing bone tumours?

Answer 1

Core biopsy under radiological guidance

Question 2

What is “shepherd’s crook deformity” a reference to?

Answer 2

Fibrous dysplasia involving the femoral head

Question 3

Recall 4 tumour-like conditions of the bone that are not actually malignant

Answer 3

1. Fibrous dysplasia
2. Fibroma (can be ossifying/ non-ossifying)
3. Reparative giant cell granuloma
4. Simple bone cyst

Question 4

How does osteochondroma mimic bone in appearance?

Answer 4

They have a cartilaginous surface overlying normal cortical + trabecular bone

Question 5

In which bones is osteochondroma most likely to present?

Answer 5

Long bones (mainly in the metaphysis)

Question 6

How will osteochondroma appear on XR?

Answer 6

“popcorn” pattern

Question 7

Is a giant cell tumour of bone benign or malignant?

Answer 7

Borderline malignant

Question 8

What is the typical age of presentation of osteochondroma?

Answer 8

20-40 years

Question 9

What is the typical age of presentation of giant cell tumour of bone?

Answer 9

20-40 years

Question 10

How do giant cell bone tumours appear under the microscope?

Answer 10

Osteoclasts on a background of ovoid cells

Looks like soap bubbles on x-ray

Question 11

What are the 3 types of malignant bone tumour?

Answer 11

Osteosarcoma (bone-forming-can give a “sunburst” appearance on x-ray, and can cause periosteum to lift, known as Codman’s triangle, pRB, TP53 association)
Chondrosarcoma (cartilage-forming- fluffy appearance)
Ewing’s sarcoma (undifferentiated mesenchymal-arises from neuroectodermal cells-onion skin appearance, 11:22 translocation)

Question 12

Recall the typical age of presentation for each of the 3 types of malignant bone tumour

Answer 12

Osteosarcoma: <30 years
Chondrosarcoma: >40 years (elderly)
Ewing’s sarcoma: 10-20 years

Question 13

Recall the typical site affected for each of the 3 types of malignant bone tumour

Answer 13

Osteosarcoma: knee
Chondrosarcoma: pelvis/ proximal skeleton
Ewing’s sarcoma: pelvis + long bones

Question 14

Recall the typical X ray appearance of each of the 3 types of malignant bone tumour

Answer 14

Osteosarcoma: Codman’s triangle, Sunburst appearance
Chondrosarcoma: fluffy calcification/moth-eaten piece of cloth
Ewing’s sarcoma: Onion-skinning of periosteum

Question 15

What is a “Codman’s triangle”?

Answer 15

The triangular area of new subperiosteal bone that is created when a lesion, often a tumour, raises the periosteum away from the bone.

Question 16

Which of the 3 types of malignant bone tumour has the best prognosis?

Answer 16

Chondrosarcoma

Question 17

What gene mutation is associated with Ewing’s sarcoma?

Answer 17

11:22 translocation

Question 18

Which type of malignant bone tumour will stain for CD99 and MICC2?

Answer 18

Ewing’s sarcoma

Question 19

Which patients are most at risk of developing Ewing’s tumour in soft tissue?

Answer 19

Immunocompromised patients

Question 20

Sources of secondary bony mets:

Answer 20

Breast
Prostate
Lungs
Thyroid
Kidneys

Question 21

Most common benign bone tumour?

Answer 21

Osteochondroma

Mainly in the metaphysis of long bones

Tumor arises from the growth plate, often leads to a lateral bony projection called a exostosis, with a hyaline cartilage cap

Question 22

What mutation is common in osteosarcoma?

Answer 22

pRB

Also seen in retinoblastoma