Clinical Oncology (1991) 3:177-179 (~) 1991 The Royal College of Radiologists

Clinical Oncology

Case Report Bone Scan Hot Spots in a Patient with Lung Cancer: Ischaemic Necrosis of Bone Mimicking Metastatic Carcinoma M. N. Gaze, E. Neville and H. W. P. Rooke Departments of Medicine and Radiology, St Mary's Hospital, Portsmouth, Hampshire, PO3 6AD, UK

Abstract. A 62-year-old man complained of a pain in his leg four months after radical surgery for a bronchial adenocarcinoma. Skeletal scintigraphy showed increased uptake of isotope in the lower femur and upper tibia corresponding to an abnormal area on the plain radiographs. Bone metastases were thought to be the most likely cause of these findings. Since the appearances were not entirely typical, bone biopsy was undertaken to confirm the diagnosis. This showed ischaemic necrosis of bone, related to a previous acute arterial occlusion. In view of the serious implications for a patient if an erroneous diagnosis of metastatic disease is made following potentially curative treatment for cancer, such a diagnosis should be proven, not assumed. Bone biopsy should be considered when solitary skeletal lesions develop in radically treated cancer patients with no other evidence of metastasis. Keywords: Aseptic, ischaemic or avascular necrosis of bone; Bone infarct; Differential diagnosis; Osseous metastasis; Skeletal scintigraphy

~TRODUCTION

Bone metastases are a common complication of bronchial carcinoma. The initial clinical suspicion is usually confirmed by plain radiographs and skeletal scintigraphy. There is rightly a natural reluctance to perform invasive investigations in patients with metastatic and incurable cancer, and so it is rare for the diagnosis to be confirmed by histology, unless surgery is needed for open reduction and internal fixation of a pathological fracture. It is important, however, to be sure that the patient does have Correspondence and offprint requests to: Dr M. N. Gaze, Department of Radiation Oncology, CRC Beatson Laboratories, Alexander Stone Building, Garscube Estate, Glasgow, G61 1BD, UK.

disseminated malignancy before a prognosis or treatment is given. Here, we report a case of suspected bone metastasis which proved on biopsy to be ischaemic necrosis of bone.

CASE REPORT

A 62-year-old man presented wiLth dyspnoea and haemoptysis after an episode of acute bronchitis. He was a lifelong smoker with chronic obstructive airways disease who eight years previously had received an aortobifemoral bypass graft for intermittent claudication. Collapse and consolidation of the right middle lobe were demonstrated on chest radiography, and fibreoptic bronchoscopy showed turnout in the right middle lobe bronchus. At thoractomy the turnout was resected by right middle and lower lobectomy. Histology showed a poorly differentiated adenocarcinoma of stage T2 N1. In the early postoperative period he suddenly developed acute ischaemia of his right leg which was due to occlusion of the right limb of his arterial graft and the right superficial femoral artery. This was effectively treated by the insertion of a crossover graft from the left limb of his original graft to the right profunda femoris artery° About four months after the resection of his carcinoma the patient developed pain in his right leg, and bone metastases were suspected. Bone scintigraphy showed two hot spots in the right ribs which were ascribed to surgical trauma, and abnormal uptake in the lower end of the right femur and upper tibia (Fig. 1). Plain radiographs of the affected leg revealed a sclerotic mottling in the distal femur and proximal tibia, corresponding with the scintigraphic abnormalities (Fig. 2). The appearances were not characteristic of metastatic disease, although atypical, osteoblastic

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Fig. 1. Skeletal scintigraphy showing increased uptake of isotope in the distal right femur.

Fig. 2. Radiograph of the right lower femur showing sclerotic mottling corresponding with the scintigraphic appearance.

secondary deposits were considered a possibility. Because of the unusual features, open biopsy of the femur was undertaken. Histology showed widespread oppositional woven bone in relation to necrotic trabeculae of lamellar bone with variable fibrosis of marrow. Tumour was not present in the biopsy, the appearances of which were consistent with healing ischaemic necrosis. There was no evidence of tumour recurrence in the next year, but the subsequent development of unequivocal lytic osseous metastases in the pelvis heralded a rapid decline. He died from disseminated malignancy eighteen months after his thoracotomy.

fracture. The reported frequency of bone involvement varies. Pain is reported in up to 20% of patients at presentation (Spiro, 1984), but the prevelence of confirmed metastases is less. Of those with inoperable lung cancer referred to a medical oncology unit, 35% had bone involvement (Napoli et al., 1973). While most cases have lytic lesions, some may be sclerotic: osteoblastic metastases occurred in nine of 110 patients (8.2%) studied by Napoli et al. They originated most often from small cell carcinoma (seven cases in 22 patients) or adenocarcinoma (two cases in 21 patients). They were not noted in patients with undifferentiated large cell or squamous carcinoma. Ischaemic necrosis of bone occurs most commonly in the femoral or humeral head, and has many causes (Nixon, 1983), including traumatic disruption of blood supply in fracture of the femoral neck, hip dislocation, slipped capital epiphysis and cervical osteotomy. Vascular occlusion may also result from sickling of hypoxic red cells in sickle cell disease, fat emboli in alcoholics with liver disease, and nitrogen bubbles in deep sea divers, caisson workers and aviators. Prolonged or high dose corticosteroid therapy may also result in ischaemic necrosis, though the mechanism remains unclear (Nixon, 1984). Patients with cancer may develop ischaemic necrosis as a result of combination

DISCUSSION

Although common things occur most commonly, rarities should not be forgotten. Where doubt remains the diagnosis should be proven not assumed. Bone metastases are common in patients with bronchial carcinoma. They may be discovered by staging investigations while the patient is asymptomatic or present with bone pain or pathological

Ischaemic Necrosis of Bone Mimicking Metastatic Carcinoma

chemotherapy regimens with or without steroids (Harper et al., 1984, Marymont and Kaufman, 1985), or following radiotherapy-induced endarteritis in bone (Langlands et al., 1977). The developing radiological appearances of ischaemic necrosis have been divided into four stages (Nixon, 1983). Stage 1, where there is no radiological abnormality progresses through irregular bone density with or without minimal collapse of the articular surface (stage 2), to an intermediate stage 3 with obvious radiographic collapse of bone and the appearance of sequestrum. In stage 4 there is extensive joint destruction with associated osteoarthritic change. This classical sequence is most obvious when the femoral head is involved. When other sites are affected the diagnosis is less easy, and the changes are liable to misinterpretation. Skeletal scintigraphy with 99mTechnetium diphosphonate usually shows increased uptake, and is of little value in the differential diagnosis; but scanning with similarly radiolabelled sulphur colloid may reveal photon-deficient areas. Several authors have commented on the difficulty of distinguishing between ischaemic necrosis and malignant disease involving bone. It is important to establish the correct cause of sclerotic bone lesions in patients with advanced Hodgkin's disease, because after chemotherapy with steroid containing cytotoxic regimens such patients may develop ischaemic necrosis mimicking bone involvement, which occurs in up to 10% of patients and is usually osteoblastic (Hope-Stone, 1979). Women irradiated for breast carcinoma may develop osteonecrosis in the upper ribs or shoulder girdle bones (Bates, 1975; Langlands et al., 1977), and subsequent radiographs are sometimes wrongly reported to show metastatic breast cancer. Cases have been reported in which an initial diagnosis of primary bone tumour has been changed to osteonecrosis after further investigation (Kjmrulff et al., 1985; Thomas et al., 1985). The ischaemic necrosis in the lower femur of our patient can be attributed to acute ischaemia follow-

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ing his arterial graft occlusion, four months prior to his symptoms developing. Because the latent period between the original insult and the appearance of ischaemic necrosis ranges from months to years, the precipitating factor may be forgotten. This case shows the importance of considering ischaemic necrosis in the differential diagnosis of patients with bronchial carcinoma who develop sclerotic bone lesions. We, therefore, urge clinicians and radiologists to remember benign disease as a possible cause of isolated bone lesions in patients previously treated for cancer, and to consider biopsy in cases of doubt. References Bates TD (1975). A prospective clinical trial of postoperative radiotherapy delivered in three fractions per week versus two fractions per week in breast carcinoma. Clinical Radiology, 26, 297-304. Harper PG, Trask C, Souhami RL (1984). Avascular necrosis of bone caused by combination chemotherapy without corticosteroids. British Medical Journal, 288, 267-268. Hope-Stone HF (1979). The diagnosis of osteo-necrosis in Hodgkin's disease - active disease or infarction? British Journal of Radiology, 52, 580-582. Kj~erulff H, Hejgaard N, Rostgaard E (1985). Necrosis of the tuberosity of the ischium mimicking neoplasm. Injury, 16, 554-556. Langlands AO, Souter WA, Samuel E, Redpath AT (1977). Radiation osteitis following irradiation for breast cancer. Clinical Radiology, 28, 93-96. Marymount JV, Kaufman EE (1986). Osteonecrosis of bone associated with combination chemotherapy without corticosteroids. Clinical Orthopaedics, 204, 150-153. Napoli LD, Hansen HH, Muggia MM, Twigg HL (1973). The incidence of osseous involvement in lung cancer, with special reference to the development of osteoblastic changes. Radiology, 108, 17-21. Nixon JE (1983). Avascular necrosis of bone: a review. Journal of the Royal Society of Medicine, 76, 681-692. Nixon JE (1984). Early diagnosis and treatment of steroid induced avascular necrosis of bone. British Medical Journal, 288,741-744. Spiro SG (1984). The diagnosis and staging of lung cancer. In: The Management of Lung Cancer, ed. Smyth JF, pp. 36-52. Edward Arnold, London. Thomas DHV, Abraham RR, Handley C, Dorrell JH (1985). Dysbaric osteonecrosis in differential diagnosis of malignant bone disease. Journal of the Royal Society of Medicine, 78, 492-493.

Receivedfor publication May 1990 Accepted July 1990

Bone scan hot spots in a patient with lung cancer: ischaemic necrosis of bone mimicking metastatic carcinoma.

A 62-year-old man complained of a pain in his leg four months after radical surgery for a bronchial adenocarcinoma. Skeletal scintigraphy showed incre...
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