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Adult Primitive Neuroectodermal Tumor: Proton MR Spectroscopic Findings with Possible Application for Differential Diagnosis¹

¹ From the Institute de Diagnostic per la Imatge (IDI), Department of Diagnostic Imaging, Hospital Duran i Reynals, CSU de Bellvitge, Autovía de Castelldefels km 2,7, 08907 L’Hospitalet de Llobregat, Barcelona, Spain (C.M., J.A., C. Aguilera, M.S., J.G.); Department of Neurosurgery, Hospital Príncipes de España, CSU de Bellvitge, L’Hospitalet de Llobregat, Barcelona, Spain (J.J.A.); and Department of Biochemistry and Molecular Biology, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Spain (C. Arús). Received October 1, 2001; revision requested December 10; revision received January 28, 2002; accepted March 14. Supported in part by the Generalitat de Catalunya (grants CIRIT XT2000 43 and SGR1999-328), the Interministerial Commission on Science and Technology (CICYT SAF1999-101), and the European Union (IST1999-10310). Address correspondence to C.M. (e-mail: cmajos@csub.scs.es).

View larger version (35K): [in a new window]   Figure 1. Flow chart shows the empiric path used for bilateral differential diagnosis of PNET. DR = discriminative resonance, 1H MRS = proton MR spectroscopy, 90% P = 90th percentile. * = First and second discriminative resonances may vary depending on the tumor type to be differentiated from PNET. ** = Non-PNET tumors were meningioma, low-grade astrocytoma, anaplastic astrocytoma, glioblastoma, and metastasis. TE = echo time.

View larger version (17K): [in a new window]   Figure 2a. Scatterplots show the distribution of normalized area values (ordinates, arbitrary units) of the resonances that allowed better differentiation of PNET (*) and other tumor types. The mean value for every tumor group is also labeled (-) and its numeric value given. (a) Scatterplot shows the distribution of the resonance that corresponds to CHO in PNET, low-grade astrocytoma (LGA) (), anaplastic astrocytoma (AA) (), and glioblastoma (GBM) (). Note the higher values for PNET (*). The tumor group showing the most overlap with PNET is anaplastic astrocytoma. Glioblastoma also shows overlap that is of low diagnostic effect, as the main differences between PNET and glioblastoma are found in LIP 1.30 (Figs 2c and 7). (b) Scatterplot shows the distribution of Ala in meningioma (MEN) () and PNET. The mean value is significantly higher in meningioma. (c) Scatterplot shows the distribution of LIP 1.30 in glioblastoma (GBM) (), metastasis (MET) (x), and PNET. The mean value is significantly higher in glioblastoma and metastasis than in PNET.

View larger version (15K): [in a new window]   Figure 2b. Scatterplots show the distribution of normalized area values (ordinates, arbitrary units) of the resonances that allowed better differentiation of PNET (*) and other tumor types. The mean value for every tumor group is also labeled (-) and its numeric value given. (a) Scatterplot shows the distribution of the resonance that corresponds to CHO in PNET, low-grade astrocytoma (LGA) (), anaplastic astrocytoma (AA) (), and glioblastoma (GBM) (). Note the higher values for PNET (*). The tumor group showing the most overlap with PNET is anaplastic astrocytoma. Glioblastoma also shows overlap that is of low diagnostic effect, as the main differences between PNET and glioblastoma are found in LIP 1.30 (Figs 2c and 7). (b) Scatterplot shows the distribution of Ala in meningioma (MEN) () and PNET. The mean value is significantly higher in meningioma. (c) Scatterplot shows the distribution of LIP 1.30 in glioblastoma (GBM) (), metastasis (MET) (x), and PNET. The mean value is significantly higher in glioblastoma and metastasis than in PNET.

View larger version (14K): [in a new window]   Figure 2c. Scatterplots show the distribution of normalized area values (ordinates, arbitrary units) of the resonances that allowed better differentiation of PNET (*) and other tumor types. The mean value for every tumor group is also labeled (-) and its numeric value given. (a) Scatterplot shows the distribution of the resonance that corresponds to CHO in PNET, low-grade astrocytoma (LGA) (), anaplastic astrocytoma (AA) (), and glioblastoma (GBM) (). Note the higher values for PNET (*). The tumor group showing the most overlap with PNET is anaplastic astrocytoma. Glioblastoma also shows overlap that is of low diagnostic effect, as the main differences between PNET and glioblastoma are found in LIP 1.30 (Figs 2c and 7). (b) Scatterplot shows the distribution of Ala in meningioma (MEN) () and PNET. The mean value is significantly higher in meningioma. (c) Scatterplot shows the distribution of LIP 1.30 in glioblastoma (GBM) (), metastasis (MET) (x), and PNET. The mean value is significantly higher in glioblastoma and metastasis than in PNET.

View larger version (116K): [in a new window]   Figure 3a. PNET. (a) Transverse T2-weighted MR image (2,175/85) shows a relatively homogeneous tumor (arrows) in the posterior fossa, adjacent to the posterior wall of the fourth ventricle. The voxel position for proton MR spectroscopy (box) is also shown. (b) Localized spin-echo proton MR spectrum (2,000/136, 128 acquisitions) of the tumor shows prominent resonances from CHO and low CR and NACC resonance. There is a small amount of LACT (Lact) and a resonance at 3.55 ppm that is attributable to Gly/MI. Some peaks (*) around 3.30 and 3.40 ppm suggest the presence of taurine in this particular case. The histologic diagnosis was PNET. The empiric algorithm satisfactorily classified this tumor as PNET at bilateral comparisons with the main tumors included in the differential diagnosis (metastasis and meningioma).

View larger version (15K): [in a new window]   Figure 3b. PNET. (a) Transverse T2-weighted MR image (2,175/85) shows a relatively homogeneous tumor (arrows) in the posterior fossa, adjacent to the posterior wall of the fourth ventricle. The voxel position for proton MR spectroscopy (box) is also shown. (b) Localized spin-echo proton MR spectrum (2,000/136, 128 acquisitions) of the tumor shows prominent resonances from CHO and low CR and NACC resonance. There is a small amount of LACT (Lact) and a resonance at 3.55 ppm that is attributable to Gly/MI. Some peaks (*) around 3.30 and 3.40 ppm suggest the presence of taurine in this particular case. The histologic diagnosis was PNET. The empiric algorithm satisfactorily classified this tumor as PNET at bilateral comparisons with the main tumors included in the differential diagnosis (metastasis and meningioma).

View larger version (145K): [in a new window]   Figure 4a. Metastasis. (a) Transverse T2-weighted MR image (2,175/85) shows a well-defined midline tumor (arrows) adjacent to the aqueduct and fourth ventricle. There is some heterogeneity with central low signal intensity and peritumoral edema. The voxel position for proton MR spectroscopy (box) is shown. (b) Localized spin-echo proton MR spectrum (2,000/136, 128 signals acquired) of the tumor shows LIP resonance at 1.30 ppm and a small amount at 0.90 ppm. This finding is highly suggestive of metastasis or glioblastoma. The diagnosis after tumor removal was metastasis. Bilateral comparison with PNET satisfactorily suggested metastasis.

View larger version (18K): [in a new window]   Figure 4b. Metastasis. (a) Transverse T2-weighted MR image (2,175/85) shows a well-defined midline tumor (arrows) adjacent to the aqueduct and fourth ventricle. There is some heterogeneity with central low signal intensity and peritumoral edema. The voxel position for proton MR spectroscopy (box) is shown. (b) Localized spin-echo proton MR spectrum (2,000/136, 128 signals acquired) of the tumor shows LIP resonance at 1.30 ppm and a small amount at 0.90 ppm. This finding is highly suggestive of metastasis or glioblastoma. The diagnosis after tumor removal was metastasis. Bilateral comparison with PNET satisfactorily suggested metastasis.

View larger version (128K): [in a new window]   Figure 5a. Meningioma. (a) Transverse T2-weighted MR image (2,175/85) shows a well-defined midline tumor (arrows). The voxel position for proton MR spectroscopy (box) is depicted. "A" marks correspond to unremovable marks made by the spectroscopic software package used. (b) Localized spin-echo proton MR spectrum (2,000/136, 128 signals acquired) of the tumor shows an inverted Ala doublet centered at 1.47 ppm that is highly suggestive of meningioma. Note also a clear resonance of GLX. The histologic diagnosis was meningioma. Bilateral comparison satisfactorily resulted in differentiation of this tumor from PNET.

View larger version (15K): [in a new window]   Figure 5b. Meningioma. (a) Transverse T2-weighted MR image (2,175/85) shows a well-defined midline tumor (arrows). The voxel position for proton MR spectroscopy (box) is depicted. "A" marks correspond to unremovable marks made by the spectroscopic software package used. (b) Localized spin-echo proton MR spectrum (2,000/136, 128 signals acquired) of the tumor shows an inverted Ala doublet centered at 1.47 ppm that is highly suggestive of meningioma. Note also a clear resonance of GLX. The histologic diagnosis was meningioma. Bilateral comparison satisfactorily resulted in differentiation of this tumor from PNET.

View larger version (136K): [in a new window]   Figure 6a. PNET. (a) Transverse fast FLAIR MR image (6,706/120/2,000; turbo factor, 15) shows a heterogeneous tumor (arrows) with a cystic and/or necrotic area. The voxel position for proton MR spectroscopy (box) is shown. (b) Localized spin-echo proton MR spectrum (2,000/136, 192 signals acquired) of the tumor shows prominent resonance from CHO and low CR and NACC resonances. A certain amount of LACT is probably overlapping with Ala. Note also a small peak (*) at 3.4 ppm that is difficult to differentiate from noise and could suggest resonance from taurine. The definitive diagnosis after partial tumor removal was PNET. Bilateral differentiation from glioblastoma satisfactorily suggested PNET.

View larger version (15K): [in a new window]   Figure 6b. PNET. (a) Transverse fast FLAIR MR image (6,706/120/2,000; turbo factor, 15) shows a heterogeneous tumor (arrows) with a cystic and/or necrotic area. The voxel position for proton MR spectroscopy (box) is shown. (b) Localized spin-echo proton MR spectrum (2,000/136, 192 signals acquired) of the tumor shows prominent resonance from CHO and low CR and NACC resonances. A certain amount of LACT is probably overlapping with Ala. Note also a small peak (*) at 3.4 ppm that is difficult to differentiate from noise and could suggest resonance from taurine. The definitive diagnosis after partial tumor removal was PNET. Bilateral differentiation from glioblastoma satisfactorily suggested PNET.

View larger version (133K): [in a new window]   Figure 7a. Glioblastoma. (a) Transverse intermediate-weighted MR image (2,175/20) shows a heterogeneous tumor (arrows) with a necrotic cystlike area in the left frontal lobe. The voxel position for proton MR spectroscopy (box) is also shown. (b) Localized spin-echo proton MR spectrum (2,000/136, 192 signals acquired) of the tumor shows LIP resonance at 1.30 ppm that is highly suggestive of metastasis or glioblastoma. The histologic diagnosis after partial tumor removal was glioblastoma. Bilateral discrimination with PNET satisfactorily suggested glioblastoma.

View larger version (19K): [in a new window]   Figure 7b. Glioblastoma. (a) Transverse intermediate-weighted MR image (2,175/20) shows a heterogeneous tumor (arrows) with a necrotic cystlike area in the left frontal lobe. The voxel position for proton MR spectroscopy (box) is also shown. (b) Localized spin-echo proton MR spectrum (2,000/136, 192 signals acquired) of the tumor shows LIP resonance at 1.30 ppm that is highly suggestive of metastasis or glioblastoma. The histologic diagnosis after partial tumor removal was glioblastoma. Bilateral discrimination with PNET satisfactorily suggested glioblastoma.