British Journal of Radiology (2006) 79, 177-178
© 2006 British Institute of Radiology
doi: 10.1259/bjr/65970261
An unusual cause and presentation of a pelvic mass
S Harish, FRCS, FRCR1,
A Rehm, FRCS2 and
P W P Bearcroft, FRCR1
Departments of 1 Radiology and 2 Orthopaedics, Addenbrooke's Hospital, Hills Road, Cambridge CB2 2QQ, UK
Correspondence: Dr S Harish, Department of Diagnostic Imaging, St Joseph's Hospital, 50 Charlton Ave E, Hamilton, Ontario, L8N 4A6, Canada.
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Clinical history
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A 19-year-old female was referred to the orthopaedic clinic with a history of limb length discrepancy. Her only complaint was that the right leg seemed shorter than the left. On physical examination, the pelvis was slanting slightly towards the right with a limited range of movement of the right hip. There was right-sided hip pain at the extremes of rotational movements and flexion. A 10 cm x 15 cm firm, non-tender mass was palpable just proximal to the anterior rim of the iliac crest. According to the patient this mass had been present for a long time. Clinically, the patient did not have a leg length discrepancy, but had a fixed pelvic obliquity causing apparent leg length discrepancy. A plain film was obtained (Figure 1
) and the appearance prompted an MR examination of the pelvis. Axial T1 weighted and fat suppressed axial T2 (Figure 2) and fat suppressed coronal T2 weighted images (Figure 3) were obtained. What do these images show?
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Findings
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Plain radiograph of the pelvis (Figure 1
) showed a large irregular, calcified, bony mass arsing from the right ilium. A diagnosis of an osteochondroma was made. Because of the size of the lesion, there was a concern that the lesion may represent a malignant chondroid lesion. MR of the pelvis (Figures 2 and 3) showed an 8 cm x 7 cm x 7 cm lesion arising from the right ilium with typical features of an osteochondroma. There was a rim of high signal on T2 weighted imaging in keeping with a cartilage cap. The cartilage cap measured up to 1 cm in thickness, but the iliac crests had not fused indicating that the patient was not skeletally mature. There were no sinister features to suggest malignant degeneration into a chondrosarcoma, but nevertheless, with a lesion of this size, malignancy could not be completely excluded. Interestingly, the right kidney could not be visualized in the MR images with some hypertrophy of the left kidney, and the lesion itself was located close to the expected anatomical site of the right kidney (Figure 3). Also, there was hypoplasia of the ipsilateral hemipelvis (Figure 1) with minor scoliosis concave to the right (Figure 3). At this point, the possibility of previous right nephrectomy and radiation to the renal bed causing this osteochondroma was invoked. Further history in fact revealed that the patient did have a right nephrectomy and partial right hepatectomy for stage 3 type Wilm's tumour at the age of 2 years, which was followed by chemotherapy and radiation of 3000 cGy to the right hemiabdomen and the tumour bed. Incision biopsy at a tertiary bone tumour centre confirmed this lesion to be an osteochondroma with no pathological features to suggest malignancy. The patient was offered excision of the lesion, but since she was not symptomatic from the lesion itself, she preferred to wait for a few years.
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Discussion
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Radiation-induced osteochondromas arise typically in patients who received radiotherapy as children, and they are indistinguishable radiologically and pathologically from a spontaneous osteochondroma. In a series of 42 patients with Wilm's tumour treated with radiotherapy and a minimum follow-up of 5 years, there was a 4.8% incidence of osteochondromas and a 2.4% incidence of sarcomas [1]. In another series of 58 children who received radiotherapy as part of therapy for bone marrow transplantation, 5 developed osteochondromas and all of these 5 children were less than 5 years of age at the time of radiotherapy with no patient who underwent radiotherapy after 5 years of age developing osteochondromas [2]. There is an average latent period of about 5–8 years before these lesions develop [2, 3] and they may be found to be enlarging until normal growth ceases and growth of tumour is maximal at times of patient's growth spurt [4]. Malignant degeneration in radiation-induced osteochondromas is uncommon and the criteria applied to spontaneous lesions such as increase in size of the lesion after epiphyses closure, increasing soft tissue mass and development of pain in the absence of an alternative explanation should be used for these as well [3, 5]. A thickened cartilage cap greater than 2 cm raises the suspicion of malignant change in an osteochondroma [5]. Only two cases have been adequately described wherein radiation-induced osteochondromas underwent malignant change [6]. Other complications of these lesions include restriction of movement at adjacent joints, bursitis and pressure on adjacent neurovascular bundle [5]. In conclusion, this is a very unusual presentation of a rare case of radiation-induced osteochondroma of the right ilium in a 19-year-old female secondary to radiotherapy, which had been performed when the patient was 2 years old. Detection of mass lesions in such young patients who are survivors of childhood cancer causes significant anxiety and psychological impact on the patients' lives. The current literature suggests very low incidence of malignant degeneration in radiation-induced osteochondromas, and awareness of this behaviour of these lesions should help the clinicians to manage them appropriately.
Received for publication November 22, 2004.
Revision received February 15, 2005.
Accepted for publication June 14, 2005.
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References
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- Paulino AC, Wen BC, Brown CK, Tannous R, Mayr NA, Zehn WK, et al. Late effects in children treated with radiation therapy for Wilm's tumour. Int J Radiat Oncol Biol Phys 2000;46:1239–46.[CrossRef][Medline]
- Taitz J, Cohn RJ, White L, Russell SJ, Vowels MR. Osteochondroma after total body irradiation: an age-related complication. Pediatr Blood Cancer 2004;42:225–9.[CrossRef][Medline]
- Libshitz HI, Cohen MA. Radiation-induced osteochondromas. Radiology 1982;142:643–7.[Abstract/Free Full Text]
- DeSimone DP, Abdelwahab IF, Kenan S, Klein MJ, Lewis MM. Radiation-induced osteochondroma of the ilium. Skeletal Radiol 1993;22:289–91.[Medline]
- Lee KC, Davies AM, Cassar-Pullicino VN. Imaging the complications of osteochondromas. Clin Radiol 2002;57:18–28.[CrossRef][Medline]
- Mahboubi S, Dormans JP, D'Angio G. Malignant degeneration of radiation-induced osteochondroma. Skeletal Radiol 1997;26:195–8.[CrossRef][Medline]
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Clinical history
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