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.

Fig. 8.5 A and B AP and lateral radiographs of tibia. There is an area of dense cortical thickening and sclerosis of the posterior tibial diaphysis. A small central lucency is only just visible. These are typical appearances of osteoid osteoma.

Fig. 8.6 CT scan demonstrates a central small lucency (arrow) containing a more dense central nidus within the thickened cortex. The appearance is diagnostic of an osteoid osteoma.

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).

Fig. 8.7 Radiograph of metacarpo-phalangeal joint of the little finger with a typical enchondroma in the proximal phalanx. The lucent lesion has produced slight medullary expansion with thinning of the overlying cortex. There is some calcification within the lesion indicating a lesion of cartilage origin.

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.

Fig. 8.8 Osteochondroma of the distal femur. The radiograph shows a bony exostosis arising from the posterior femur and directed away from the adjacent joint. The cartilage cap is not visible.

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.

Fig. 8.9 Histology of giant cell tumour showing large osteoclastic multinucleate giant cells (arrows) with interspersed mononuclear tumour cells. The nuclei of the two cell types are very similar. (Haematoxylin and eosin ×400.)

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).

Fig. 8.10 A and B Radiographs of giant cell tumour in the proximal tibia. There is a lucent lesion in the metaphysis, with extension into the epiphyseal region extending to the articular surface of the knee. In a patient with fused epiphyses the most likely diagnosis is a giant cell tumour.

Fig. 8.11 MRI of the same patient confirms that the tumour reaches superiorly to the articular cortex. The lesion is however confined to the bone with no evidence of extension through the bony cortex.

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.

Chondromyxoid fibroma and chondroblastoma

Both of these benign bone tumours are extremely rare and readers should consult larger textbooks for details of their clinical presentation, imaging and treatment.

Osteosarcoma (osteogenic sarcoma)

This is predominantly a tumour of childhood or adolescence, occurring most commonly in the 10–25 age group. When it occurs in later life it is often a complication of Paget’s disease (osteitis deformans) (p. 66).

Pathology. An osteosarcoma arises from primitive bone-forming cells. The commonest sites are the lower end of the femur, the upper end of the tibia, and the upper end of the humerus – that is, in those areas in which, prior to epiphysial fusion, most active growth is occurring. The tumour begins in the metaphysis – that is, the part of the shaft that is adjacent to the epiphysial plate. It destroys the bone structure and eventually bursts into the surrounding soft tissues, though it seldom crosses the epiphysial cartilage into the epiphysis itself (Fig. 8.12). The histological appearance varies widely, because any type of connective tissue may be represented. Thus the tumour may be composed largely of fibrous tissue, of cartilage or of myxomatous tissue; but characteristically there will always be found, in some parts of the tumour, areas of neoplastic new bone or osteoid tissue that indicate the true nature of the lesion, and in some cases newly formed bone is abundant (Fig. 8.16). The tumour metastasises early by the blood stream, especially to the lungs and sometimes to other bones.

Fig. 8.16 Histological appearance of a typical osteosarcoma with areas of immature bone osteoid formation (arrows) and numerous atypical malignant stromal cells showing nuclear pleomorphism and mitotic activity. (Haematoxylin and eosin ×400.)

Clinical features. The usual presentation is local bone pain associated with a gradually increasing swelling. Examination reveals a diffuse firm thickening near the end of a bone, close to the joint. The overlying skin is warmer than normal because of the vascularity of the tumour; and the part may be so distended by tumour that the skin appears stretched and shiny.

Imaging. Plain radiographs show irregular medullary and cortical destruction of the metaphysis. Later the cortex appears to have been ‘burst open’ at one or more places by the soft tissue extension (Fig. 8.17), but there are always vestiges of the original cortex. MR scanning allows accurate delineation of the tumour size and the extent of invasion of the soft tissues (Fig. 8.18). There is usually evidence of new bone formation under the corners of the aggressive periosteal reaction (Codman’s triangle) (Fig. 8.17B). Occasionally well-marked radiating spicules of new bone are seen within the tumour (‘sun-ray’ appearance) (Fig. 8.17A). In a parosteal osteosarcoma, a variant that may occur in older patients with a better prognosis, there may be profuse formation of new bone on the surface of the cortex.

Fig. 8.17 A and B AP and lateral radiograph of knee. There is irregular sclerosis of the metaphysis which does not cross the epiphysis. The aggressive bone-forming lesion has breached the cortex with a periosteal reaction producing the characteristic Bryant’s triangle and ‘sun-ray’ spiculation.

Fig. 8.18 A Radiograph of osteosarcoma of the femur. There is an area of ill-defined lucency in the mid shaft associated with some periosteal reaction. B MR of same patient. The area of marrow abnormality is seen to be extending far into the distal femur with a large soft tissue mass surrounding the femur not evident on the plain film.

Radioisotope (technetium) scanning will show increased uptake at the site of the tumour and can provide additional information on the intramedullary spread by any ‘skip’ lesions, though these are normally detected by MRI scanning.

A chest radiograph may show pulmonary metastases (Fig. 8.19), but CT scanning of the lung fields (Fig. 8.20) is now mandatory for pre-treatment staging as it can detect small pulmonary metastases before they are apparent in plain radiographs.

Fig. 8.19 Pulmonary metastases in a case of osteosarcoma of the tibia. Such metastases are the usual cause of death.

Fig. 8.20 CT of chest showing two intrapulmonary metastases posteriorly in the left lung.

Diagnosis. In atypical cases an osteosarcoma may be confused with subacute osteomyelitis, or with other bone tumours such as chondrosarcoma, malignant fibrous histiocytoma, giant-cell tumour, Ewing’s tumour, or even metastatic tumour. A representative piece of the tumour should always be removed by closed needle or open biopsy and sent for histological examination.

Prognosis. Prior to the introduction of effective chemotherapy, when surgical excision or amputation was the only treatment, the mortality was in the region of 80%. Recent advances in adjuvant treatment added to surgical ablation have changed the prognosis markedly for the better, with increased survival time and often lasting cure.

Treatment. The introduction of new powerful cytotoxic drugs for adjuvant chemotherapy has revolutionised the treatment of these tumours, because of their ability to prevent or delay the appearance of pulmonary micrometastases. The drugs currently used include high-dose methotrexate, doxorubicin, cisplatin, and ifosfamide in combinations which are the subject of multi-centre controlled trials. They all have major side effects and should only be used at treatment centres skilled in their use. Chemotherapy is usually commenced before surgical treatment, and is continued intermittently for 6 months to a year after ablation of the tumour. Commencing chemotherapy before operative treatment allows the pathologist to assess the response of the tumour to the drugs by histological examination of the resected specimen. The ability of chemotherapy to control local recurrence and distant metastatic spread has permitted the increasing use of ‘limb salvage surgery’ as an alternative to amputation. In selected cases, based on accurate surgical staging from biopsy and modern imaging techniques, it is possible to undertake radical resection and replacement with a metallic prosthesis or a massive bone graft. Recent reports have shown over 70% disease-free survival after 5 years by this approach in patients with osteosarcoma, with no increase in local recurrence rates when compared with amputation.

Chondrosarcoma of bone

A chondrosarcoma is a malignant tumour derived from cartilage cells, and it tends to maintain its cartilaginous character throughout its evolution.

Pathology. It may develop in the interior of the bone (central chondrosarcoma) or upon its surface (peripheral chondrosarcoma). A central chondrosarcoma occurs most commonly in the femur, the tibia, or the humerus. It may arise de novo, without there having been a pre-existing lesion (Figs 8.21 and 8.22), or it may arise from malignant transformation of a previously existing enchondroma (especially in the condition known as dyschondroplasia, Ollier’s disease or multiple chondromatosis (p. 65).

Fig. 8.21 Radiograph of proximal femur with a central chondrosarcoma. The lytic lesion has produced endosteal scalloping, indicating an aggressive lesion, and shows calcification indicating a chondroid matrix.

Fig. 8.22 MR of same patient. Demonstrates the extent of the femoral lesion which is similar to that seen on the plain film and is still confined to bone.

A peripheral chondrosarcoma, on the other hand, tends usually to affect a flat bone such as the innominate bone (Figs 8.23 and 8.24), the sacrum, or thescapula, and it generally arises from malignant transformation of a previously existing osteochondroma (especially in the condition of diaphysial aclasis or multiple exostoses (p. 63)).

Fig. 8.23 Plain radiograph of the pelvis showing a large lobulated calcified mass arising from the right iliac wing, which proved to be a low-grade peripheral chondrosarcoma.

Fig. 8.24 MR of same patient as in Fig. 8.23 shows a much larger mass than is apparent on the plain film. This consists of non-calcified cartilage and suggests that the chondrosarcoma has developed in a cartilage-capped exostosis arising from the pelvis.

Histologically, a chondrosarcoma may be highly cellular (Fig. 8.25). The cartilage cell nuclei tend to be swollen, and double nuclei may be seen. These features, suggestive of malignancy, may be found in only a few microscopic fields, the remainder of the tissue appearing relatively benign.

Fig. 8.25 Histological appearance of chondrosarcoma with an extensive chondroid matrix, containing scattered atypical chondrocytes with nuclear pleomorphism and some spindle cell morphology. (Haematoxylin and eosin ×400.)

Clinical features. The patient is usually in the 30–60 age group, who complains of pain and local swelling, often in an area where there was known to be a previous lesion, such as multiple exostoses or Ollier’s disease. The tumour grows slowly and may attain a large size.

Imaging. Radiographically, a central chondrosarcoma is seen to grow at the expense of the cortical bone with endosteal scalloping and may result in pathological fracture (Fig. 8.21). In contrast a peripheral chondrosarcoma shows as a large mass growing outwards from the surface of the bone (Fig. 8.23). Both types characteristically show blotchy areas of calcification within the tumour mass. Magnetic resonance scanning is essential to define the soft tissue extension of the tumour (Figs 8.22 and 8.24).

Prognosis. A chondrosarcoma grows slowly and does not metastasise early; so the prognosis, depending on the grade of the tumour, is somewhat more favourable than it is for osteosarcoma. Because of the variable grades and slow growth of chondrosarcoma the overall survival rate may be over 75%, though in high-grade lesions this may fall to 20%.

Treatment. Since adjuvant chemotherapy is not effective against chondrosarcoma, surgery must remain the treatment of choice. Wide surgical margins must be achieved to permit complete resection, though in some low-grade lesions or borderline malignancy it may be possible to undertake local excision or even curettage. In very large high-grade tumours or following local recurrence, amputation may still be required.

Malignant fibrous histiocytoma of bone

This rare highly malignant tumour includes many of the lesions once classified as fibrosarcoma, because their histology shows a predominance of fibroblast- type cells mixed with primitive histiocytes. It affects adults in the 20–60 age group, mainly occurring in the diaphysis of long bones, presenting with pain, swelling and sometimes pathological fracture.

Imaging with radiographs and MR shows permeative bone destruction from a large soft tissue mass with no sclerosis or periosteal reaction.

Treatment is similar to osteosarcoma, requiring radical surgery and adjuvant chemotherapy.

Ewing’s¹ tumour (endothelial sarcoma of bone)

Ewing’s tumour (endothelial sarcoma of bone) is an uncommon but highly malignant sarcoma that arises in bone marrow.

Pathology. The tumour is commonest in the shaft of the femur, tibia, or humerus. Unlike osteosarcoma, it arises in the diaphysis rather than the metaphysis of a bone. It probably develops from endothelial elements within the bone marrow, though the precise cell of origin is not known. The tumour tissue is soft and vascular. As it expands it gradually destroys the bone substance. There is a striking reaction beneath the periosteum, where abundant new bone is formed in successive layers (Fig. 8.13). Histologically the tumour consists of sheets of uniform small round cells (Fig. 8.26). The tumour metastasises early through the blood stream, especially to the lungs, and sometimes to other bones.

Fig. 8.26 Histological appearance of Ewing’s sarcoma with sheets of cells, containing round or oval nuclei, but with very little intercellular stroma. (Haematoxylin and eosin ×400.)

Clinical features. Children and adolescents in the 5–20 age group are the usual victims. Typically, there is local pain with rapidly increasing firm swelling over one of the long bones, usually near the middle of the shaft (in contrast to osteosarcoma which arises at the metaphysis). Local symptoms may be accompanied by fever, weight loss and general malaise. On examination the swelling is diffuse or fusiform, and of firm consistency. The overlying skin becomes stretched and warmer than normal due to the large size and vascularity of the tumour mass.

Imaging. Plain radiographs show destruction of bone substance with concentric layers of subperiosteal new bone (‘onion-peel’ appearance) (Fig. 8.27). MR scanning will reveal the extent of the large soft tissue mass of the tumour (Fig. 8.28). An isotope bone scan is also required in staging to detect any multifocal lesions. A radiograph or CT scan of the chest may show pulmonary metastases.

Fig. 8.27 (left) Radiograph of Ewing’s sarcoma in the proximal tibia in a child. The lateral cortex is destroyed and there is periosteal elevation at the lower margin of the lesion.

Fig. 8.28 (right) MR of the same patient as in Fig. 8.27. This shows there is extensive involvement of the tibial shaft, the cortex is breached and there is a large associated soft tissue mass.

Diagnosis. In atypical cases there may be confusion with subacute osteomyelitis, because of the systemic disturbance and raised ESR. In particular, it may be confused histologically with a metastasis from a suprarenal neuroblastoma. A percutaneous needle biopsy should be undertaken when the tumour is suspected.

Prognosis. Until recent years Ewing’s tumour was uniformly fatal – usually from pulmonary metastases, with fewer than 15% of patients surviving beyond 5 years. The advent of adjuvant chemotherapy and improved radiotherapy has changed this gloomy outlook, and now 5-year survival rates can be expected in 50–60% of cases.

Treatment. Chemotherapy differs from that used for osteosarcoma and a number of different drug combinations have been used and continue to evolve. A combination of vincristine, cyclophosphamide, dactinomycin, and doxorubicin is commonly recommended and is commenced as adjuvant therapy prior to any operative treatment. The tumour itself may be treated by radical operative excision with prosthetic replacement, or by amputation. Radiotherapy may be used as an alternative to operation, since the tumour is radiosensitive. Surgical excision with a special prosthesis adjustable for progressive limb growth is preferred for lower limb lesions, particularly in young children where leg length discrepancy and joint contractures may follow radiotherapy. Radiotherapy is usually reserved for upper limb tumours and for tumours at inaccessible sites such as the pelvis or spine.

Myeloma (myelomatosis; plasmacytoma)

This is a tumour of bone marrow, occurring in older adults aged 50–70, often presenting as a single lesion but later spreading to involve the bone marrow at other sites. It is usually ultimately fatal, though modern treatment regimens may produce very long-term remission for up to 10 years.

Pathology. It arises from the plasma cells of the bone marrow and is disseminated to many parts of the skeleton through the blood stream, so that by the time the patient seeks advice the tumour foci are usually multiple, affecting chiefly the bones that contain abundant red marrow. Less commonly the tumour may present as a solitary bone plasmacytoma (Fig. 8.29) with spread to other skeletal sites only after months or years. The lesions are mostly small and circumscribed (Figs 8.14 and 8.30) but occasionally large: the bone is simply replaced by tumour tissue and there is no reaction in the surrounding bone. Pathological fracture is common, especially in the spine (Fig. 8.30). Histologically the tumour consists ofa mass of small round cells of plasma-cell type: the cells may be somewhat larger than normal plasma cells, and less uniform (Fig. 8.31).

Fig. 8.29 Radiograph of pelvis. There is a large lytic lesion of the right iliac wing. The imaging findings are non-specific, but biopsy indicated this to be a solitary plasmacytoma.

Fig. 8.30 Multiple myeloma. Left: Part of pelvis and femur, showing numerous small tumour foci. Right: Spine, showing diffuse rarefaction, with partial collapse of the bodies of the second and fourth lumbar vertebrae.

Fig. 8.31 Multiple myeloma. Sheets of cells resembling plasma cells. (Haematoxylin and eosin ×400.)

Clinical features. In most cases the tumour affects adults past middle age. There is general ill health, with local pain at one or more of the tumour sites, or sometimes a pathological fracture. On examination the patient is pale from the associated anaemia due to suppression of red marrow function. There is often local tenderness over the affected bones, but there may be no obvious swelling or deformity unless pathological fracture has occurred. The patient is prone to develop infections due to the suppression of normal antibody production.

Imaging. Radiographs show multiple punched out lytic lesions, especially in bones containing red marrow, such as ribs, vertebral bodies, pelvic bones, skull, and proximal ends of femur and humerus (Fig. 8.30). Sometimes there is diffuse rarefaction of bone (Table 6.2, p. 77).

MRI scanning is potentially useful for imaging multiple skeletal lesions, particularly in suspected spinal involvement because of the superior soft tissue resolution it provides.

Investigations. There is microcytic anaemia. The erythrocyte sedimentation rate is increased. Bence Jones protein is present in the urine in more than half the cases. Serum globulin is increased, often so much that the albumin–globulin ratio (normally 2:1) is reversed. Marrow biopsy usually shows a profusion of plasma cells which can be characterised by immunohistochemistry and cytogenetics to give more help in planning treatment and predicting prognosis.

Diagnosis. Iliac or sternal marrow biopsy will often confirm the diagnosis when the clinical and radiographic features are equivocal.

Prognosis. The tumour is usually fatal, though its progress can often be checked for several years by the improving treatment regimens.

Treatment. The tumour foci respond to radiotherapy for a while, and pain is well relieved. The mainstay of chemotherapy in the past has been melphalan, an alkylating agent, which was sometimes used in conjunction with prednisolone. Newer drug combinations are showing improved results using thalidomide, or one of its analogues, with dexamethasone and a proteasome inhibitor, bortezomib. In a favourable case remission for up to 4 years may be gained. The possible place of bone marrow stem cell transplantation is also under trial. When hypercalcaemia is a problem treatment with bisphosphonates to inhibit excessive bone resorption may be required.

Secondary (metastatic) tumours in bone

Secondary malignant tumours in bone are much more common than primary tumours; but whereas most primary malignant bone tumours occur in children or young adults, secondary tumours generally occur in later life.

Pathology. The tumours that metastasise most readily to bone are carcinomas of the lung, breast, prostate, thyroid, and kidney (hypernephroma). Metastases occur most commonly in the parts of the skeleton that contain vascular marrow, especially the vertebral bodies, ribs, pelvis, and upper ends of the femur and humerus. The bone structure is simply destroyed and replaced by tumour tissue (Fig. 8.15). Pathological fracture is therefore very liable to occur.

Clinical features. Pain is the usual main symptom, but sometimes the disability is insignificant until a pathological fracture occurs. The spine is frequently involved, often with progressive neurological symptoms as well as local pain, from pressure on nerve roots or the spinal cord. In advanced widespread metastatic disease the patient may develop symptoms of hypercalcaemia,with nausea, vomiting, dehydration, and even coma. The primary tumour can usually be demonstrated.

Analysis of the different types of clinical presentation has shown that 50% of patients present initially with bone pain, 25% with pathological fracture, 15% with paraplegia or paraparesis, and 10% with local swelling.

Imaging. In plain radiographs the bone appears to have been eaten away so that there is a clear circumscribed area of lysis, without any reaction in the surrounding bone (Fig. 8.32). Exceptionally, new bone is laid down within the metastasis, causing marked sclerosis – the exact opposite to the usual osteolytic lesion. This type is almost confined to secondary deposits from prostatic carcinoma. In cases of diffuse infiltration there may be widespread osteoporosis (Table 6.2, p. 77). A radiograph or CT scan of the chest should always be obtained because of the possibility that metastases may be present in the lungs.

Fig. 8.32 A Typical appearance of a metastatic carcinoma in the humerus. The primary tumour was in the lung. With increasing destruction of bone, pathological fracture is likely to occur. B AP radiograph of tibia showing a solitary renal metastasis. There is a lytic expansile lesion in the proximal tibia with breach of the medial cortex indicating an aggressive lesion and the patient has a known renal carcinoma.

Technetium isotope scanning is the best technique for detecting occult metastatic deposits in the skeleton, as areas of increased uptake (Fig. 2.14B). These may be apparent long before the lesions are visible in plain radiographs, making it a very sensitive screening method. Magnetic resonance imaging is an even more sensitive method of screening, particularly for the detection of spinal metastases.

Investigations. In prostatic metastases the content of acid phosphatase in the plasma is usually increased above the normal range. The increase is specifically in the tartrate labile or ‘prostatic’ phosphatase. Hypercalcaemia may sometimes occur when there is excessive bone resorption from widespread bone metastases.

Treatment. Radiotherapy is a valuable palliative treatment, particularly in more localised disease. Chemotherapy is sometimes appropriate (see p. 117). Radio-active iodine is valuable for metastases from carcinoma of the thyroid. Hormone analogue therapy may be appropriate for metastases from the breast or prostate, and in selected cases adrenalectomy and hypophysectomy have proved worthwhile in slowing the progress of the disease when other measures have failed. In the presence of life-threatening hypercalcaemia, treatment by bisphosphonates is valuable in that it inhibits further bone resorption and may also relieve bone pain. Local splintage may be required, but metallic internal fixation, or even custom prosthetic replacement of bone, is used increasingly for the treatment of impending or pathological fracture of the long bones as a means of maintaining independent function. Strong analgesics and sedatives may be required and a multi-disciplinary team is essential for the overall management of severe intractable pain.

Bone changes in leukaemia and lymphoma

This is a convenient place to note that changes may occur in the skeleton in leukaemia and in Hodgkin’s disease or related lymphomas. In leukaemia the changes are due to infiltration of bone by proliferating white cells, and they are seen most commonly in subacute lymphatic leukaemia in children. Characteristically there are zones of rarefaction with delicate subperiosteal new bone formation in the metaphysial regions of the femur or humerus, or in the spine or pelvis. Leukaemia is also an occasional cause of diffuse widespread rarefaction of the skeleton (Table 6.2, p. 77).

In Hodgkin’s disease or the related lymphomas there may be osteolytic lesions in the proximal limb bones or in the spine or pelvis, denoting destruction and replacement by tumour tissue.