Clinical features of 12 cases with peripheral primitive neuroectodermal tumors of soft tissue

Objective: To clarify the clinical characteristics including basic data, imaging, and pathological features of peripheral primitive neuroectodermal tumors (pPNETs) in patients. Methods: A retrospective analysis was conducted on the clinical data of 12 pathologically-confirmed pPNETs patients treated in the Affiliated Hospital of Jining Medical University from January 2012 to December 2017. All the patients were examined by CT and MRI imaging, and the imaging findings were evaluated. The pooled tumor specimens were subject to routine H&E staining and immunohistochemical staining for observation of pathological features. Nine patients who had received surgical resection were followed for 1 year and their rates of tumor recurrence and metastasis were assessed. Results: Twelve enrolled patients had a mean age of 22.2 years (range, 8-50 years), with much more males than females (at a ratio of 2 to 1). The tumors were all pPNETs of soft tissue. The manifestations of pPNETs on computed tomography (CT) images showed uneven density nodules with necrosis and cystic changes, and heterogeneous enhancement mass. On MR images, the tumors were isointense or hypo-intense on T1-weighed image (T1WI), and isointense or hyper-intense on T2-weighed image (T2WI). The regions with tumor cystic degeneration or necrosis showed hypo-intense on T1W images and hyper-intense on T2W images. Typical Homer-Wright rosette forming was noted by H&E staining. The results of immunohistochemical staining demonstrated that the positive rates of CD99, neuron-specific enolase (NSE), Vimentin, synaptophysin (Syn), and S-100 proteins were 100%, 50%, 33.3%, 58.3% and 16.7%, respectively. After one-year follow-up, the recurrence rate of pPNETs was 33.3% and the metastasis rate was 25% in patients with surgical resection of pPNETs. Conclusion: pPNETs of soft tissue were not specific on CT and MRI images, and the definitive diagnosis was still dependent on pathological examination.