Evaluation of (18)F-FDG PET and MRI in differentiating benign and malignant peripheral nerve sheath tumors.
OBJECTIVE
To compare 18F-FDG PET/CT and MRI for differentiating benign and malignant peripheral nerve sheath tumors (BPNSTs and MPNSTs) and correlate imaging characteristics with histopathology.


METHODS
Patients with pathologically proven PNSTs undergoing 18F-FDG PET/CT were retrospectively reviewed. PET/CTs and, if available, MRIs were analyzed, noting multiple imaging characteristics and likely pathology (benign or malignant).


RESULTS
Thirty-eight patients with 23 BPNSTs and 20 MPNSTs were analyzed. MPNSTs had higher SUVmax (10.1 ± 1.0, 4.2 ± 0.4, p < 0.0001), metabolic tumor volume (146.5 ± 39.4, 21.7 ± 6.6 cm(3), p = 0.01), total lesion glycolysis (640.7 ± 177.5, 89.9 ± 23.2 cm(3)*g/ml, p = 0.01), and SUVmax/LiverSUVmean (5.3 ± 0.5, 2.0 ± 0.2, p < 0.0001). All lesions with SUVmax < 4.3 were benign. All lesions with SUVmax > 8.1 were malignant. SUVmax cutoff of 6.1 yielded 90.0 % sensitivity and 78.3 % specificity for MPNSTs. SUVmax/LiverSUVmean cutoff of 3.0 yielded 90.0 % sensitivity and 82.6 % specificity. MPNSTs more commonly had heterogeneous FDG activity (p < 0.0001), perilesional edema (p = 0.004), cystic degeneration/necrosis (p = 0.015), and irregular margins (p = 0.004). There was no difference in lesion size, MRI signal characteristics, or enhancement. Expertly interpreted MRI had 62.5-81.3 % sensitivity and 94.1-100.0 % specificity while PET had 90.0-100.0 % sensitivity and 52.2-82.6 % specificity for diagnosing MPNSTs.


CONCLUSIONS
FDG PET and MRI play a complementary role in PNST evaluation. Multiple metabolic parameters and MRI imaging characteristics are useful in differentiating BPNSTs from MPNSTs. This underscores the potential critical role of PET/MRI in these patients.
Department of Radiology, Mayo Clinic, Charlton Building North, 1st Floor, 200 First Street SW, Rochester, MN, 55905, USA. broski.stephen@mayo.edu.
Stephen M
SM
Broski
Department of Radiology, Mayo Clinic, Charlton Building North, 1st Floor, 200 First Street SW, Rochester, MN, 55905, USA.|Department of Immunology, Mayo Clinic, Rochester, MN, 55905, USA.
Geoffrey B
GB
Johnson
Department of Radiology, Mayo Clinic, Charlton Building North, 1st Floor, 200 First Street SW, Rochester, MN, 55905, USA.
Benjamin M
BM
Howe
Department of Radiology, Mayo Clinic, Charlton Building North, 1st Floor, 200 First Street SW, Rochester, MN, 55905, USA.
Mark A
MA
Nathan
Department of Radiology, Mayo Clinic, Charlton Building North, 1st Floor, 200 First Street SW, Rochester, MN, 55905, USA.
Doris E
DE
Wenger
Department of Neurosurgery, Mayo Clinic, Rochester, MN, 55905, USA.|Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN, 55905, USA.
Robert J
RJ
Spinner
Department of Radiology, Mayo Clinic, Charlton Building North, 1st Floor, 200 First Street SW, Rochester, MN, 55905, USA.|Department of Neurosurgery, Mayo Clinic, Rochester, MN, 55905, USA.
Kimberly K
KK
Amrami
D000293:Adolescent; D000328:Adult; D000368:Aged; D003937:Diagnosis, Differential; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009442:Neurilemmoma / Q000000981:diagnostic imaging*; D000072078:Positron Emission Tomography Computed Tomography; D055815:Young Adult
D019788:Fluorodeoxyglucose F18
MPNST; MRI; Nerve sheath; PET/CT; Tumor