British Journal of Radiology (2007) 80, e109-e112
© 2007 British Institute of Radiology
doi: 10.1259/bjr/16630393
Intracranial myeloid sarcoma: conventional and advanced MRI findings
B Hakyemez, MD
1
N Yildirim, MD
1
O Taskapilioglu, MD
2
C Erdogan, MD
1
S Aker, MD
3
S Yilmazlar, MD
4 and
M Parlak, Prof
1
Uludag University School of Medicine, Departments of 1 Radiology, 2 Neurology, 3 Pathology and 4 Neurosurgery, Bursa, Tukey
Correspondence: Dr Bahattin Hakyemez, Radiology, Uludag University Medical School, Uludag Universitesi Tip Fakultesi, Radyoloji ABD, Gorukle, Bursa, Gorukle, 16023, Turkey. E-mail: bahattinh{at}hotmail.com
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Abstract
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Chloroma (myeloid or granulocytic sarcoma) is a rare type of tumour comprising immature granulocytic cells. It generally accompanies acute myeloid leukaemia and, rarely, other myeloproliferative disorders. When presenting as dural-based mass lesions, radiological differential diagnosis includes meningioma, metastasis and lymphoma. There is a limited number of descriptions of chloromas mimicking dural-based masses in the literature. We present preliminary diffusion-weighted MR, perfusion-weighted MR and MR spectroscopy findings of an intracranial myeloid sarcoma.
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Introduction
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Leukaemias develop as a result of neoplastic proliferation of haematopoietic cells. Central nervous system (CNS) complications are seen in approximately 20–50% of leukaemic patients [1]. Myeloid sarcoma, formerly named granulocytic sarcoma or chloroma, consists of neoplastic granulocytic precursors and myeloblasts. It is a focal lesion seen in 2% of acute myelogenous leukaemia patients [2]. Most common involvement sites are bone, soft tissue, periostium, lymph nodes and skin [3]. CNS invasion often occurs in meningeal and sometimes in parenchymal form. Meningeal infiltration may be focal or diffuse. Dura mater, leptomeninges, or both may be involved [4]. When myeloid or granulocytic sarcoma produces focal thickening of leptomeninges, it may mimic dural-based meningioma, metastasis and lymphoma. This form of involvement is very rare and there is a limited number of articles in the literature describing conventional radiological findings alone [5]. In addition to well-described conventional MR findings, we present diffusion and chemical characteristics, and vascularity, of myeloid sarcoma in a patient with acute myelogenous leukaemia.
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Case report
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A 54-year-old male was diagnosed with acute myelogenous leukaemia (subtype M2) in 2003, was then in remission for 2 years after chemotherapy and finally was admitted to our hospital with new onset diplopia and severe headache. He underwent conventional, diffusion-weighted, perfusion-weighted MRI and MR spectroscopy with 1.5 T MR. Two extraaxial and dural-based lesions in the temporo-occipital and anterior interhemispheric regions were depicted on routine examination sequences. The lesions were 6.5 x 5 x 3.5 cm and 2.5 x 2 x 2 cm, respectively. They were isointense with the grey matter on T1 weighted images, but isointense or slightly hypointense on T2 weighted images. Only the larger lesion localized to the temporo-occipital area had surrounding oedema. Both lesions enhanced homogeneously after contrast media administration. There was no cystic or necrotic component in the lesions (Figure 1
). Diffusion-weighted MRI was performed with single-shot spin echo, echoplanar sequence (repetition time/echo time (TR/TE) 10 000/126 ms, slice thickness 5 mm and slice gap 1 mm). Trace images were obtained by simultaneous application of diffusion-sensitive gradients in three different directions. The b-value was taken as 0 and 1000 s mm–2. Trace diffusion-weighted images showed slight hyperintensity of the lesions when compared with brain parenchyma. Lesions were markedly hypointense in apparent diffusion coefficient (ADC) images. While the ADC values of the lesions were 0.49 x 10–3 and 0.52 x 10–3 mm2 s–1, respectively, the value of normal brain parenchyma was 0.75 x 10–3 mm2 s–1 (Figure 2a). Proton MR spectroscopy was performed with point-resolved surface coil spectroscopic sequence (PRESS) and single voxel (TR/TE 1500/270 ms). The MR spectrum of the larger lesion showed no N-acetyl aspartate (NAA, 2.02 parts per million (&NAA, 2.02 parts per million (ppm)) peak, while there was a significant increase in the choline peak (3.22 ppm) (Figure 2b). Cerebral perfusion-weighted MRI was performed with a first-pass contrast-enhanced T2 weighted single-shot, gradient echo, echoplanar sequence using a rapid bolus (5 ml s–1) of 0.1 mmol kg–1 MRI contrast material through an 18-gauge or 20-gauge intravenous line. Parameters of the sequence were: TR/TE 2000/54 ms; flip angle 40°; bandwidth 62.5; field of view 28 x 21 cm; matrix 96 x 128; slice thickness 6 mm; slice gap 1 mm. In total, 55 images were taken from each slice in 110 s. Cerebral blood volume (CBV) images and relative (r)CBV ratios of the images were obtained. Almost the entire lesion demonstrated lower signal intensity than brain parenchyma on CBV images and there was a slightly colour-coded area at the periphery of the lesions. Mean rCBV ratios of the lesions were 1.58 and 1.22, respectively (Figure 2c). With these findings, biopsy was carried out. Histopathological diagnosis was reported as myeloid sarcoma (Figure 3).
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Figure 1. 54-year-old male with acute myelogenous leukaemia. A lesion in the right temporo-occipital region appears isointense with brain parenchyma on (a) T1 weighted images, while it is (b) isointense/hypointense on T2 weighted images, (c, d) with slight surrounding oedema and homogeneous contrast enhancement after gadolinium injection. (e) Another lesion bordering the anterior interhemispheric fissure is seen. Both the lesions are extracranial and dural based.
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Figure 2. With(a) trace diffusion-weighted images, the lesion appears slightly more hyperintense than the brain parenchyma, while it is (b) markedly hypointense in apparent diffusion coefficient (ADC) images. The ADC value of the lesion is 0.49 x 10–3 mm2 s–1. The MR spectrum shows no N-acetyl aspartate (NAA, 2.02 ppm) peak, but (c) a prominent increase in the choline peak (Cho, 3.22 ppm). (d) Cerebral blood volume (CBV) images show that most parts of the lesion have lower intensity than the brain parenchyma without prominent enhancement. There is a slight enhancement around the lesion. The relative celebral blood volume ratio of the lesion is approximately 1.58.
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Figure 3. (a) Oval-shaped, diffusely scattered malignant lymphoid cells with hyperchromatic nuclei and (b) normal glial tissues in the left upper corner. (c) Immunohistochemical stains shows staining of tumour cells with myeloperoxidase.
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Discussion
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Granulocytic sarcoma, often associated with myelogenous leukaemia, is a focal solid mass lesion consisting of immature granulocytes. Sarcomas may appear before, during or after systemic leukaemia treatment. In our case, lesions appeared after the treatment during the remission phase. Focal lesions are mostly seen in bones, peritoneum, lymph nodes, skin and epidural structures. Intracranial granulocytic sarcomas infiltrate the parenchyma after destruction of the pial–glial barrier following the invasion of periostium by leukaemia cells arising from the bone marrow via haversian canals [6]. Moreover, leukaemia cells may infiltrate dural and subarachnoidal spaces through the arachnoidal veins. Supra- or infratentorially localized lesions are generally in the form of extraaxially dural-based focal masses. Although rare, intraaxial lesions are also reported [7].
Conventional MR findings of myeloid sarcomas are widely described in the literature. Typically, the lesion appears isointense or slightly hypointense when compared with normal grey matter in T1 and T2 weighted images. It generally shows homogeneous contrast enhancement [8]. Associated bone marrow involvement and low signal intensity on T2 weighted images may generally be helpful in differentiating these tumours from other intracranial lesions [9]. Myeloid sarcomas have also been reported as appearing necrotic prior to treatment [10]. In our case, lesions show the same signal intensity as the brain parenchyma on T1 weighted images, whereas they were isointense or slightly hypointense on T2 weighted images with homogeneous enhancement after gadolinium administration. There was no necrotic area in the lesions. Bone marrow adjacent to the lesion appeared normal. With these findings, it is difficult to differentiate the lesion from extraaxial tumours [5].
In our case, lesions appeared slightly hyperintense compared with normal brain parenchyma in diffusion-weighted trace images, whereas they were apparently hypointense in ADC images. ADC values of the lesions were 0.49 x 10–3 and 0.52 x 10–3 mm2 s–1. The ADC values of the lesions being less than those of normal brain parenchyma is a marker of the decrease in water diffusion. The decrease in ADC values may be explained by the presence of many abnormal granular or myeloid cells in the lesion, a decrease in the amount of fluid in the extracellular space, minimal vascularity within the lesion and tight junctions in the intercellular space. However, low ADC values may be seen in atypical meningiomas, lymphomas and also in some of the metastases [11, 12]. For this reason, it is clear that the diffusion-weighted MR technique alone cannot provide adequate information to differentiate myeloid sarcoma from other extraaxial tumours.
Perfusion-weighted MRI findings of most of the intracranial lesions have been described, whereas perfusion findings of myeloid sarcomas have not been reported. In our case, except for the minimal colour coding in the periphery of the lesion, almost the entire lesion presented the same as or less intensity than the brain parenchyma. Mean rCBV ratios of the lesions were 1.58 and 1.22, representing the hypovascularity of the mass. Paucity of neovascularity also depicted in the histopathological specimens may account for the low rCBV ratios and low colour-coded appearance of the lesion. Extraaxial lesions such as meningiomas and choroid plexus tumours are highly vascular lesions. rCBV ratios of meningiomas have been reported to be higher than those of intraaxial tumours [13]. We propose that perfusion-weighted MRI may be a guide in cases that are difficult to differentiate from meningiomas. On the other hand, lymphomas, whose conventional MRI findings can be similar to those of other extraaxial tumours, are generally avascular or hypovascular. Perfusion-weighted MRI is able to show the hypovascularity and rCBV ratios to be much lower than those of malignant masses, particularly of high-grade gliomas and metastases [13]. For this reason, differentiating myeloid sarcomas from other extraaxial tumours such as lymphoma with perfusion-weighted MRI is not possible. Intracranial dural-based metastases such as meningiomas are generally hypervascular on perfusion-weighted MRI, and high rCBV ratios are depicted [14].
Proton MR spectroscopy is a non-invasive method of measuring biochemical components of the tissue within a spectrum. Although different MR spectroscopic findings in many different tumoural lesions have been described in the literature, there have been no such data for myeloid sarcomas [15]. We found only a markedly increased choline peak in our case. As NAA is not found in extraaxial masses, an NAA peak is not an expected finding. Therefore, MR spectroscopic findings of myeloid sarcomas and extraaxial tumours may share common characteristics.
As a result, myeloid sarcoma must be kept in mind as an initial diagnosis when an extraaxial dural-based mass lesion is encountered in an acute myelogenous leukaemia patient. Myeloid sarcoma tends to be markedly hyperintense on diffusion-weighted MR images and exhibits a marked decrease in ADC values when compared with normal brain parenchyma. It is hypovascular on perfusion-weighted MRI, and MR spectroscopy findings are not helpful in differentiating the lesion from other extraaxial tumours.
Received for publication September 2, 2005.
Revision received October 24, 2005.
Accepted for publication November 24, 2005.
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References
|
|---|
- Bleyer HW. Central nervous system leukemia. In: Henderson HS, Lister TA, editors. Leukemia. Philadelphia, PA: Saunders, 1990: 207–24
- Liu PI, Ishimaru T, McGregor DH, Okada H, Steer A. Autopsy study of granulocytic sarcoma (chloroma) in patients with myelogenous leukemia, Hiroshima–Nagasaki 1949–1969. Cancer 1973;31:948–55.[CrossRef][Medline]
- Muss HB, Moloney WC. Chloroma and other myeloblastic tumors. Blood 1973;42:721–8.[Abstract/Free Full Text]
- Azzarelli B, Roessman U. Pathogenesis of central nervous system infiltration in acute leukemia. Arch Pathol Lab Med 1977;191:203–5.
- Ahn JY, Kwon SO, Shin MS, Kang SH, Kim YR. Meningeal chloroma (granulocytic sarcoma) in acute lymphoblastic leukemia mimicking a false meningioma. J Neuro-Oncol 2002;60:31–5.[CrossRef][Medline]
- Barnett MJ, Zussman WV. Granulocytic sarcoma of the brain: a case report and review of the literature. Radiology 1986;160:223–5.[Abstract/Free Full Text]
- Kao SC, Yuh WT, Sato Y, Barloon TJ. Intracranial granulocytic sarcoma (chloroma): MR findings. J Comput Assist Tomogr 1987;11:938–41.[Medline]
- Parker K, Hardjasudarma M, McClellan RL, Fowler MR, Milner JW. MR features of an intracerebellar chloroma. AJNR Am J Neuroradiol 1996;17:1592–4.[Abstract]
- Williams MP, Olliff JFC, Rowley MR. CT and MR findings in parameningeal leukemic masses. J Comput Assist Tomogr 1990;14:736–42.[Medline]
- Vinters HV, Gilbert JJ. Multifocal chloromas of the brain. Surg Neurol 1982;17:47–51.[CrossRef][Medline]
- Filippi CG, Edgar MA, Ulug AM, Prowda JC, Heier LA, Zimmerman RD. Appearance of meningiomas on diffusion-weighted images: correlating diffusion constants with histopathologic findings. AJNR Am J Neuroradiol 2001;22:65–72.[Abstract/Free Full Text]
- Yamasaki F, Kurisu K, Satoh K, Arita K, Sugiyama K, Ohtaki M, et al. Apparent diffusion coefficient of human brain tumors at MR imaging. Radiology 2005;235:985–91.[Abstract/Free Full Text]
- Cha S, Knopp EA, Johnson G, Wetzel SG, Litt AW, Zagzag D. Intracranial mass lesions: dynamic contrast-enhanced susceptibility-weighted echo-planar perfusion MR imaging. Radiology 2002;223:11–29.[Abstract/Free Full Text]
- Yildirim N, Hakyemez B, Erdogan C, Parlak M. Role of diffusion and perfusion-weighted MR imaging in differentiating meningioma from solitary dural metastasis. Riv Neuroradiol 2005;18:160
- Castillo M, Kwock L. Proton MR spectroscopy of common brain tumors. Neuroimaging Clin North Am 1998;8:733–52.
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Abstract
Introduction
