Bone Tumours: General And Benign

Question 1

Why is MRI used for staging of bone masses?

Answer 1

The major role of MRI is in local staging, particularly for high-grade malignant tumours such as osteosarcoma, where the intraosseous extent ( Fig. 47.5A ), identification of ‘skip’ lesions ( Fig. 47.5B ) and involvement of the neurovascular bundle ( Fig. 47.5C ) and adjacent joint ( Fig. 47.5D ) can all be assessed with great accuracy

Question 2

What factors do you take into consideration when determining if malignant or benign bone lesion?

Answer 2

Location
Rate of growth
Periosteal rxn
Matrix mineralization

Question 3

Name the different types of chondroid benign tumors with radiographic findings

Answer 3

Chondroma - Most enchondromas arise centrally in the phalanges and metacarpals. Lesions are typically metaphyseal or diaphyseal with epiphyseal location accounting for only 2–5%. Enchondromas are often eccentric and mostly (75%) solitary. They are typically wellcircumscribed, lobulated or oval lytic lesions, which may expand the cortex ( Fig. 47.6 ). Size at presentation ranges from 10 to 30 mm

Osteochondroma - lesion appears as an outgrowth from the normal cortex, with which it is continuous. Pedunculated lesions have a long slim neck ( Fig. 47.11A ) whereas sessile lesions have a broad base with the bone of origin ( Fig. 47.11B ). As the lesion grows, the marrow cavity extends into the exostosis

Chondroblastoma - lesion is usually spherical or lobular with a fine sclerotic margin ( Fig. 47.14 ). Matrix mineralization is demonstrated in only 10% radiographically, although it is much more commonly seen at CT. Linear periosteal reaction is present in 30–50% of cases, usually distant to the epiphyseal tumour. MRI shows variable SI on T2-weighted images ( Fig. 47.15 ), including hypointensity and fluid levels due to secondary aneurysmal bone cyst (ABC) change in 15% of cases. Associated marrow and soft tissue oedema and reactive joint effusion are almost invariable.

Chondromyxoid fibroma - the proximal tibial shaft, chondromyxoid fibroma appears as an eccentric, lobulated lesion with a sclerotic margin ( Fig. 47.16 ). Periosteal reaction and soft tissue extension are uncommon and matrix calcification is seen in only 12.5% of lesions[23]. MRI shows no particular diagnostic features. Outside its classical location, it has no characteristic appearances.

Question 4

What features are in keeping with chondroma Vs chondrosarcoma outside of hands and bones?

Answer 4

age under 20 years; chondrosarcoma is rare under this age 2 a purely medullary lesion consisting of well-formed circular, curvilinear or nodular calcific densities (‘popcorn’ calcification) without focal lytic areas 3 a well-defined round or elliptical margin 4 no cortical destruction, periosteal new bone formation or soft tissue mass 5 slow growth.

Question 5

Name the different types of benign osteoid masses and their radiology findings.

Answer 5

Osteoma - they are homogeneously dense lesions with smooth or lobulated margins.

Osteoid osteoma - characteristic feature of the lesion is the nidus, which may appear lucent, sclerotic or of mixed density depending upon the degree of mineralization. By arbitrary definition, the nidus of an osteoid osteoma measures no more than 10–15 mm in diameter and most do not exceed 5 mm ( Fig. 47.18 ). The nidus is surrounded by a region of reactive medullary sclerosis and periosteal reaction, the degree of which depends upon the age of the patient and the location within the bone

Osteoblastoma - lesion is predominantly lytic, measuring 10–100 mm in diameter, with larger lesions showing a greater degree of matrix mineralization ( Fig. 47.24 ). Spinal lesions result in scoliosis with the tumour located at the apex of the concavity of the curve, where expansion or absence of the pedicle may be seen. CT often reveals occult calcification, which can be punctate, nodular or generalized. Larger lesions may result in bony expansion with or without a surrounding shell of reactive bone.

Question 6

What are the radiographic features of a giant cell tumour?

Answer 6

GCT is classically a subarticular, eccentric, lytic lesion with a geographic, non-sclerotic margin. However, a poorly defined margin indicative of a more aggressive lesion may be identified in 10–15% of cases. Involvement of the subchondral or apophyseal bone is seen in 95–99% of GCTs at presentation, although lesions arising in the immature skeleton involve the metaphysis adjacent to the growth plate. The tumour usually measures 5–7 cm in size at presentation. Apparent trabeculation and cortical expansion are common features ( Fig. 47.32 ) but periosteal reaction is seen in 10–15% of cases, indicating healing of a pathological fracture. Cortical destruction with extra-osseous extension may occur in up to 50% of cases. Sacral lesions typically present as lytic destructive lesions extending to the margin of the sacroiliac joint

Question 8

Name the different types of benign vascular tumours?

Answer 8

Hemangioma, lymphangioma, glomus tumour

Question 9

Name the benign cystic bone lesions.

Answer 9

Simple bone cyst
Aneurysmal bone cyst

Question 10

Name the benign bone masses of fibrous origin.

Answer 10

FCD
Non ossifying fibroma
BFH
Desmoplastic fibroma