Bone tumours and other local conditions

8 Bone tumours and other local conditions



Co-written by Nigel Raby



TUMOURS OF BONE


Primary bone tumours, both benign and malignant, are relatively uncommon in comparison with the malignancies arising in other tissues of the body. They are also much less common than metastatic (secondary) tumours which affect the skeleton by blood stream spread from primary carcinoma of the breast, prostate, lung or kidney.


The importance of primary bone tumours is not their frequent occurrence, but the difficulty they may present in diagnosis and treatment and the need to distinguish them from a number of tumour-like lesions that affect bone. Tumours originating in bone arise from mesenchymal tissue and if malignant are termed sarcoma. They are normally classified by the predominant cell type in the lesion, which may be bone, cartilage or fibrous tissue (Table 8.1).


Table 8.1 Classification of primary bone tumours





















































Benign Malignant
Arising from bone
Osteoma Osteosarcoma
Osteoid osteoma  
Osteoblastoma  
Giant-cell tumour  
Arising from cartilage
Enchondroma Chondrosarcoma
Osteochondroma (cartilage capped exostosis)  
Chondromyxoid fibroma  
Chondroblastoma  
Arising from fibrous tissue
Fibrous cortical defect Malignant fibrous histiocytoma (MFH)
Non-ossifying fibroma  
Fibrous dysplasia  
Tumours of uncertain origin
Simple bone cyst Ewing’s sarcoma
Aneursymal bone cyst Adamantinoma

Clinical features. Bone tumours may present clinically with local pain unrelated to activity, local swelling, limp, pathological fracture, or a combination of these symptoms. Many benign tumours may be asymptomatic and are detected as a chance finding on a radiograph taken for unrelated indications. To reach an accurate and rapid diagnosis may require access to a skilled multi-disciplinary team of radiologist, pathologist, and oncologist, as well as an orthopaedic surgeon. This is particularly important where a malignant tumour is suspected since this may require complex and extended management utilising adjuvant therapy as well as surgical treatment.


Imaging of bone tumours. Bone tumours are still best evaluated by plain films. MR scanning is required to identify the full extent of the tumour and its relationship to key anatomical structures. However, the differentiation of the most likely tumour type is still best undertaken by careful evaluation of the plain film findings.


In evaluating any lesion of the bone the following key observations will allow a correct diagnosis to be made in the majority of cases.


Age of the patient. Many tumours are most commonly found in specific age groups. Ewing’s sarcoma and simple bone cysts occur in children and young adults. Chondrosarcoma generally affects patients over the age of 40.


Single or multiple lesions. Most true primary bone tumours are solitary lesions. The presence of multiple lesions suggests bone metastases, though less commonly these may occur in myeloma or lymphoma.


Site of tumour. The bone involved and the site of involvement; whether epiphysis, diaphysis or metaphysis is important. Certain tumours have a predilection for particular bones and some occur most typically in certain parts of the bone. Giant cell tumours are almost always found in a subarticular position, i.e. epiphyseal location.


Margin of the lesion. Slow-growing tumours have well-defined sometimes sclerotic margins and are most likely benign. Rapidly growing lesions will have ill-defined margins and appear to permeate diffusely into the surrounding bone. While this typically indicates a malignant process, other rapidly progressing conditions, such as acute osteomyelitis, can give a similar appearance.


Appearance of matrix. Lesions of mainly cartilage tissue will tend to show areas of calcification. A lesion arising from bone-forming cells may contain areas of ossification. If either of these findings is present then the differential diagnosis is narrowed considerably.


Periosteal reaction. If present, a periosteal reaction gives clues as to the nature of the underlying lesion. A thick well-organised periosteal reaction implies a slow-growing lesion, as for example with osteoid osteoma. A periosteal reaction consisting of layers of thin periosteum implies rapid growth and is generally indicative of a rapidly growing malignant lesion.


Breach of cortex. Destruction of the cortex indicates an aggressive invasive lesion.


Soft tissue mass. If present extension into soft tissues is also evidence of a rapidly growing aggressive lesion.


Of the above the most helpful in narrowing the differential diagnosis is the age of the patient and the site of the tumour. With these two pieces of information alone it is possible to suggest the correct diagnosis in the majority of patients.


Other investigations. Blood tests should be undertaken routinely, though these rarely provide a definitive diagnosis. A raised white cell count with an increased erythrocyte sedimentation rate and C-reactive protein suggests the possibility of a bone infection. Hypercalcaemia suggests extensive bone resorption from hyperparathyroidism, or the presence of multiple bone metastases or myeloma deposits. Multiple myeloma can be confirmed when the plasma proteins show a very high globulin level, while prostatic carcinoma spread is accompanied by a raised serum acid phosphatase.


Biopsy. In the majority of cases it is necessary to undertake a biopsy of material from the lesion for histological and bacteriological examination to reach a final definitive diagnosis. The biopsy may be an open procedure, or a closed needle or trephine technique may be used. The closed technique may be guided by CT scanning, but gives very little material for additional investigations, such as immunohistochemistry or cytogenetics. Needle biopsy should only be used where advice is available from an expert bone pathologist with the necessary technical resources for processing small tissue samples. Once diagnosed the treatment of the lesion depends on whether it is benign or malignant and will be described in more detail for the individual types of tumour.



BENIGN TUMOURS OF BONE


It would be inappropriate to give a detailed description of every type of benign tumour, but the general principles in their management will be illustrated for four of the more common types encountered in practice. These are:











Osteoid osteoma


This is a benign circumscribed lesion that may arise in the cortex of long bones or occasionally in the cancellous bone of the spine. It affects young patients aged 10–35 and is three-times commoner in males.


Pathology. The characteristic feature is the formation of a small nidus of osteoid tissue, usually less than 0.5 cm diameter, surrounded by a reactive zone of dense sclerotic new bone formation (Fig. 8.1).


Clinical features. They usually present with increasingly severe, but well-localised, deep aching pain and sometimes local bone tenderness. The pain is worse at night and is eased by aspirin or NSAIDs, a diagnostic feature.


Imaging. Plain radiographs typically show local sclerotic thickening of the shaft that may obscure the small central nidus within the area of rarefaction (Fig. 8.5). The nidus is best seen on a fine cut CT scan (Fig. 8.6) and also exhibits intense uptake on an isotope bone scan.




Treatment. In younger patients some osteomas may resolve spontaneously after several months, but most require surgical treatment. Removal of the central nidus results in resolution of the reactive bone formation and dramatic relief of symptoms. This can be achieved by open surgical excision or curettage, but increasingly less-invasive methods are being used. Where the necessary equipment is available, a CT-guided needle can be inserted into the nidus and the lesion ablated with radiofrequency coagulation.



Chondroma


This is a tumour composed of translucent hyaline cartilage, usually presenting in the 15–50 age group.


Pathology. There are two forms of chondroma: in the commonest type the tumour grows within a bone and expands it (enchondroma) (Fig. 8.2); in the other more rare form it grows outward from a bone (periosteal chondroma or ecchondroma). Most periosteal chondromas arise in the hands or feet, or from flat bones such as the scapula or ilium. They often reach a large size and are more prone to develop malignant change. Enchondromas are fairly common in the long bones, but over 50% occur in the small bones of the hands and feet. The affected bone is expanded by the tumour and its cortex is much thinned; so pathological fracture is common and usually the presenting feature. Many remain asymptomatic and are only discovered as chance findings on radiographs taken for other purposes.


Imaging. Central enchondromas expand the bone with thinning, but not erosion, of the cortex and exhibit a variable degree of mineralisation or speckled calcification (Fig. 8.7).



Multiple enchondromata of the major long bones occur mainly in the distinct, but rare, clinical condition known as dyschondroplasia (multiple chondromatosis or Ollier’s disease) (p. 65). In this disorder, which begins in childhood, enchondromata arise in the region of the growing epiphysial cartilages (growth plates) of several bones: they interfere with normal growth at the epiphysial plate and consequently may lead to shortening or deformity (see Fig. 6.4A).


Occasionally an enchondroma undergoes malignant change, becoming a chondrosarcoma, usually in one of the major long bones rather than in the small bones of the hands or feet. Clinically this should be suspected when there is a sudden increase in size of the swelling or if the lesion becomes painful.


Treatment. A chondroma is often best left alone. If it causes a fracture or is unsightly it should be removed by curettage and the defect filled with bone graft.



Osteochondroma (osteocartilaginous exostosis)


This is the commonest benign tumour of bone, usually presenting in the 10–20 age group.


Pathology. The tumour originates in childhood from the growing epiphysial cartilage plate, but as the bone grows in length the outgrowth gets ‘left behind’ and tends to point away from the adjacent joint. It frequently grows outwards from the bone like a mushroom with a bony stalk in continuity with the cortex of the underlying bone (Fig. 8.3). Less commonly the lesion may be sessile with a more broad-based origin. The bony stalk has a larger cap of cartilage which continues to grow until the cessation of skeletal growth.


The ordinary osteochondroma is single; but in the condition known as diaphysial aclasis (multiple exostoses) (p. 63) the tumours affect several or many bones. The risk of malignant change to a chondrosarcoma is higher in these multiple lesions than in the solitary lesion and should be suspected if the tumour continues to enlarge or becomes painful after puberty.


Clinical features. The tumour may be noticed as a circumscribed hard swelling near a joint, but is usually painless. It may become painful due to pressure effects on adjacent nerve or vascular structures, or from the formation of an overlying pseudobursa, though increase in size and pain should always be regarded with suspicion.


Imaging. Plain radiographs show the mushroom-like stalk of the bony tumour (Fig. 8.8), but not the larger cartilaginous cap until this calcifies once skeletal maturity is reached. Patients with known lesions should be warned to seek referral for further imaging if their swelling enlarges or becomes painful.



Treatment. The tumour should be excised if it causes pain or if it enlarges after puberty and must be sent for routine histological examination to exclude any malignant change.



Giant-cell tumour (osteoclastoma)


This is an important tumour because, though generally classed as benign, it tends to recur after local removal or curettage. It occurs most commonly in young adults in the 20–40 age group. In about 10% of cases it behaves as a frankly malignant tumour, metastasising through the blood stream to the lungs.


Pathology. The commonest sites are the lower end of the femur, the upper end of the tibia, the lower end of the radius, and the upper end of the humerus – that is, at those ends of the long bones at which most growth occurs. It may also occur in the spine and sacrum. Characteristically it occurs in the end of the bone, occupying the epiphysial region and often extending almost to the joint surface (Fig. 8.4). It destroys the bone substance, but new bone forms beneath the raised periosteum, so that the bone end becomes expanded and pathological fracture is common.


Histologically the tumour consists of abundant mononuclear oval or spindle-shaped stromal cells profusely interspersed with giant cells that may contain as many as fifty nuclei (Fig. 8.9), hence the name ‘giant cell tumour’. The giant cells possibly represent fused conglomerations of the oval or spindle-shaped stromal cells, which may frequently show mitotic figures, though this is not necessarily indicative of malignant change.



Clinical features. The symptoms are pain at the site of the tumour and a gradually increasing local swelling. Sometimes the patient is made suddenly aware that something is wrong by the occurrence of a pathological fracture. Examination reveals a bony swelling which may be tender on firm palpation.


Imaging. Radiographs show lytic destruction of the bone substance, with expansion of the cortex, but no sclerotic rim or periosteal reaction (Fig. 8.10). A few bony trabeculae may remain within the tumour giving a faintly loculated appearance. The tumour tends to grow eccentrically, and often extends as far as the articular surface of the bone. Magnetic resonance imaging will help to determine the amount of soft tissue extension of the tumour (Fig. 8.11).




Treatment. This depends upon the site of the tumour. Curettage of the contents with a high-speed burr is the standard method of treatment for most giant cell tumours, though this is associated with a high rate (20–25%) of recurrence. This rate can be reduced to less than 10% by the use of adjuvant treatment applied to the lining of the cavity after curettage. Methods used include the chemical phenol, freezing with liquid nitrogen, or the insertion of polymethylmethacrylate bone cement. In addition to its exothermic reaction on any residual cells, the cement has the added advantage of providing support to the subchondral bone and cartilage of the articular surface of the joint. In some bones, or after multiple recurrences, it may be possible to excise the tumour and replace it with allograft bone or a metal prosthesis, without undue functional compromise. Sites where this is possible include the distal radius, distal femur, and proximal tibia.


Radiotherapy is sometimes used and is capable of bringing about permanent cure, but there is a risk that it may itself induce malignant change, perhaps many years later. It should therefore be confined to tumours at sites that are inaccessible to operation, particularly in the spinal column and sacrum.



Jun 5, 2016 | Posted by in ORTHOPEDIC | Comments Off on Bone tumours and other local conditions

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