18F-FDG PET/CT combined with diagnosis CT scan in evaluation of peripheral nerve schwannoma: a review of 20 cases

Abstract：Objective To retrospectively assess the imaging findings of peripheral nerve schwannoma in 18F-FDG PET/CT combined with diagnosis CT.Methods Twenty patients with pathologically confirmed schwannomas were included in the study (8 men and 12 women;age range, 40~83 years;mean age, 63.3±14.0 years).18F-FDG PET/CT imaging and contrast-enhanced CT in twenty patients were analyzed, including the SUVmax, location, diameter, shape, margin, attenuation, enhancement pattern and extent, invasion into adjacent bone, all of which were observed and recorded.Results Most cases (16/20) were incidentally detected.All of the tumors were solitary and ovoid (n=15) or round (n=5) in shape.Seven tumors were located in the paravertebral and three were found in the supraclavicular fossa and four were found in hemithorax and four were found in cervical part and the other two were found in the right thigh and back individually.The average diameter of the tumors was (2.84±1.04) cm (range, 1.5~5.7 cm).The average CT Hunsfield Unit (HU) was (24.2±10.5) HU (range,-2.2 to 39.2 HU).There was no correlation between Hu and diameter (P=0.199).Schwannomas on unenhanced CT showed either hypoattenuation (fifteen cases) or isoattenuation (five cases) to the muscles.The tumors appeared homogenous considering attenuation in fourteen patients and heterogeneous in six patients on contrast-enhanced CT.Twenty tumors showed mild (fourteen cases) to marked (six cases) enhancement on contrast-enhanced CT.Associated features, including vessel invasion, were absent in all cases, but one case showed calcification.The mean SUVmax for schwannoma was 2.88±1.06 (range: 1.0~5.3).There was correlation both between SUVmax and diameter and Hu (P=0.028, P=0.045).Conclusion Although schwannomas may show high accumulation in 18F-FDG PET/CT imaging, unenhancement and enhancement CT are helpful for preoperative diagnosis and surgical planning in patients with schwannomas.