Granulomatous conditions

There are three disorders of the reticuloendothelial system that affect bone; all are rare, but they are important because they can be mistaken for tumours:

1. Eosinophilic granuloma.

2. Hand–Schüller–Christian disease.

3. Gaucher’s disease.

Eosinophilic granuloma

The lesions of eosinophilic granuloma are ‘punched-out’ holes in the skull and elsewhere. Radiologically, the lesions resemble metastases or bone cysts (Fig. 20.1). The ‘holes’ contain a soft brown tissue.

B9780443067181000234/f020-001-9780443067181.jpg is missing

Fig. 20.1

Eosinophilic granuloma of the rib.

The condition is not fatal and may regress spontaneously.

Hand–Schüller–Christian disease

This condition is similar to eosinophilic granuloma except that the lesions are paler and the brain is often involved, particularly around the pituitary. The condition is slowly progressive and may be fatal.

Gaucher’s disease

Gaucher’s disease is a systemic disorder in which an abnormal fatty substance (kerasin) is deposited in the liver and other tissues. Bone involved in Gaucher’s disease contains irregular cysts and cavities visible radiologically. Affected bones, particularly the femoral head and condyles, may collapse and make joint replacement necessary.

Tumours

Radiological appearance of bone tumours

When looking at bone tumours on a radiograph, ask the following questions:

Radiological features of bone tumours

1. Is the tumour creating bone or destroying bone?

2. Is the cortex of the bone intact, broken or eroded?

3. If intact, is the cortex thinner than normal and, if so, has it been indented from outside or inside the medullary cavity?

4. Is the medullary cavity wider than normal?

5. Does the shape of the tumour suggest that it is lifting the periosteum off the bone? If it is, there may be a small triangle of bone at the edge of the tumour, known as a Codman’s triangle, which is often seen in malignant tumours.

6. If the tumour is fusiform, is there an ‘onion skin’ appearance? This is often seen in Ewing’s tumour and other rapidly growing lesions.

7. Is there any sunray radial calcification? This is often seen in tumours, particularly osteogenic sarcoma.

Classification of bone tumours

The classification of bone tumours should reflect the cell of origin. They can be further subclassified into benign and malignant tumours (Table 20.1).

**Table 20.1** A simple classification of benign and malignant bone tumours according to cell of origin
	Benign	Malignant
Fibrogenic	Simple cyst	Malignant fibrous
	Aneurysmal bone cyst	Hystiocytoma
	Fibrous dysplasia
	Fibrous cortical defect	Fibrosarcoma
Chondrogenic	Enchondroma	Chondrosarcoma
	Periosteal chondroma
	Osteochondroma
	Chondromyxoid fibroma
	Chondroblastoma
Osteogenic	Osteoid osteoma	Osteosarcoma
	Osteoblastoma
	Ossifying fibroma
Unknown origin	Giant cell	Ewing’s
Unknown origin		Synovial sarcoma
Bone marrow		Myeloma
Bone marrow		Lymphoma

Simple bone islands (Fig. 20.2) are of no particular significance, although they are often striking on X-ray.

B9780443067181000234/f020-002-9780443067181.jpg is missing

Fig. 20.2

Cortical bone islands.

Benign bone tumours

Fibrogenic

Fibrous cortical defect (Fig. 20.3). This most common abnormality has a characteristic oval X-ray appearance with a sharp margin and often multilocular. No specific treatment is required.

B9780443067181000234/f020-003-9780443067181.jpg is missing

Fig. 20.3

(a), (b) Fibrous cortical defect at the lower end of femur.

Fibrous dysplasia. This can present in mono- or polyostotic forms and is seen more commonly between the second and third decades. The radiographic appearance is of a ground-glass expansile lesion, often with a bowing of the affected bone. A ‘shepherd’s crook’ deformity is seen in the proximal femur as a result of this bowing and possible multiple fractures. The polyostotic form can be associated with hypothyroidism, vitamin D-resistant rickets and the Cushing syndrome. Albright’s syndrome includes the polyostotic dysplasia with café-au-lait spots and precocious puberty. The lesions are reasonably characteristic on X-ray but occasionally a biopsy is required. When painful, these are adequately treated with curettage and bone grafting. Occasionally there can be an associated fracture, although this is rare.

Simple bone cyst (Fig. 20.4). These cysts may occur during growth and are commonly located adjacent to the epiphyseal plate. They are usually asymptomatic until pathological fracture occurs. The radiographic appearances show a well defined radiolucent lesion, often with this pathological fracture.

B9780443067181000234/f020-004-9780443067181.jpg is missing

Fig. 20.4

(a) A pathological fracture through a simple bone cyst of the humerus; (b) the fracture has united and the bone cyst is less obvious.

Bone scans confirm a decreased uptake in the area and treatment is unnecessary unless there is a risk of fracture. These cysts can heal spontaneously after a fracture, but when in doubt aspiration and an injection of methylprednisolone acetate has an 80–90% success rate. Curettage and bone grafting is occasionally necessary.

Aneurysmal bone cyst (Fig. 20.5

Only gold members can continue reading. Log In or Register to continue