British Journal of Radiology (2004) 77, 57-59
© 2004 British Institute of Radiology
doi: 10.1259/bjr/83483923
Thallium-201 single-photon emission computed tomography in the detection of retroperitoneal schwannoma
T Nakahara, MD
1
H Fujii, MD
1
J Hashimoto, MD
1
H Yabe, MD
2
H Morioka, MD
2 and
A Kubo, MD
1
Departments of 1 Radiology and 2 Orthopaedic Surgery, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan
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Abstract
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We describe a patient with retroperitoneal schwannoma whose tumour was detectable by 201Tl single-photon emission computed tomography (SPECT). Physiologic uptake in the alimentary tract did not hamper the interpretation on SPECT images. Uptake by the tumour extending along the spinal nerve root was well recognised in axial and coronal images. Our results suggest that 201Tl SPECT may be useful in the detection of retroperitoneal schwannomas.
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Introduction
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Thallium-201 (201Tl) chloride has been used for myocardial perfusion imaging. Recently, this tracer has proven to be of value for tumour imaging, especially in the assessment of the viability of brain tumours and musculoskeletal tumours [1]. However, to our knowledge there are no published reports on 201Tl imaging of retroperitoneal schwannoma. We describe here the case of a patient with retroperitoneal schwannoma whose tumour was detectable by 201Tl single-photon emission computed tomography (SPECT).
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Case report
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A 54-year-old woman with a 12 year history of pain in her back and left leg who was being treated with painkillers was admitted to our hospital for orthopaedic surgery because of increasing pain. MRI of the pelvis revealed a soft-tissue mass along the first sacral nerve root on the left side, suggesting a neurogenic tumour (Figure 1
). Since the clinical symptoms and the tumour size suggested possibility of malignant tumour, thallium imaging was taken into consideration in order not only to evaluate the possibility of malignancy but also to investigate the presence of metastatic lesions [2]. After detailed explanation of the purpose of 201Tl study, informed consent was obtained from the patient.
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Figure 1. MRI of the pelvis in a patient with retroperitoneal schwannoma. (a) Axial T2 weighted MR images show a paraspinal mass spreading the spinal nerve foramen (arrowheads). (b) Coronal T2 weighted MRI shows a well-defined mass with low (Antoni A) and high (Antoni B) signal intensities (arrowheads).
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201Tl planar scintigraphy was performed 15 min after injection of 4 mCi of 201Tl chloride. The planar image revealed increased uptake of the tracer near the left sacroiliac joint (Figure 2). SPECT of the pelvis performed following planar scintigraphy showed that this uptake site was identical to the lesion shown on MRI (Figure 3). Physiologic uptake in the intestine did not interfere with the interpretation on SPECT images.
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Figure 2. Planar 201Tl scintigraphy image. An area of increased uptake near the left sacroiliac joint is noted.
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Figure 3. 201Tl SPECT image of the pelvis. (a) Axial SPECT images show increased uptake site extending along the spinal nerve root (arrows), likely representing neurogenic tumour. (b) Coronal SPECT images show an elongated mass corresponding to the lesion on MRI.
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Surgical removal of the sacral nerve root tumour revealed a schwannoma with no malignant component. Patient's symptoms improved completely after surgery.
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Discussion
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201Tl scintigraphy is reported to be useful in the evaluation of many kinds of tumours, although there are few reports involving abdominal or intrapelvic tumours. This is probably because physiologic uptake of 201Tl in the intestine is a critical shortcoming of this method. Therefore, it may be difficult to apply 201Tl planar scintigraphy to tumours located in the abdomen and pelvis. Evaluation of tumour uptake is limited by the projection of the intestine on the planar image.
Since tomographic imaging allows precise anatomic identification, SPECT can be useful in the detection of intrapelvic tumours, as shown in our patient. In particular, 201Tl SPECT may be useful for tumours located in/near the skeleton. Faint (or absence of) 201Tl uptake by the skeleton, one of the remarkable properties of 201Tl chloride, may contribute to the easy detection of such tumours. Furthermore, in our patient paraspinal neurogenic tumour was highly suggested on 201Tl SPECT images because an area of uptake by the tumour extending along the spinal nerve root was well recognised in axial and coronal images.
MRI is useful in the diagnosis of neurogenic tumours, although it is occasionally difficult to differentiate these tumours from other soft-tissue tumours [3]. Differential diagnoses may include some malignant tumours. Recently, positron emission tomography (PET) is reported to be helpful in differentiating malignant from benign neurogenic tumours [4, 5]. Thus, it is suggested that functional imaging is a useful adjunct to MRI or CT scans. This report may provide the potential for the clinical application of 201Tl SPECT to retroperitoneal schwannomas.
Received for publication October 9, 2002.
Revision received January 23, 2003.
Accepted for publication April 24, 2003.
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References
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- Hirai K, Umesaki N, Sumi T, Ishiko O, Kanaoka Y, Ogita S, et al. Combined diagnostic imaging for retroperitoneal schwannoma. Oncol Rep 2001;8:773–5.[Medline]
- Ahmed AR, Watanabe H, Aoki J, Shinozaki T, Takagishi K. Schwannoma of the extremities: the role of PET in preoperative planning. Eur J Nucl Med 2001;28:1541–51.[CrossRef][Medline]
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Abstract
Introduction
