Hybrid peripheral nerve sheath tumours: MRI features with pathological correlation in 24 cases

Area of Science:

• Radiology
• Oncology
• Pathology

Background:

• Hybrid peripheral nerve sheath tumors (HPNST) are rare neoplasms.
• Accurate diagnosis of HPNST is crucial for appropriate management.
• Understanding the specific MRI characteristics of HPNST is important for differentiating them from other nerve sheath tumors.

Purpose of the Study:

• To delineate the magnetic resonance imaging (MRI) features of histologically confirmed hybrid peripheral nerve sheath tumors (HPNST).
• To identify common and uncommon MRI findings associated with HPNST.
• To compare MRI features of HPNST with those typically seen in benign peripheral nerve sheath tumors.

Main Methods:

• Retrospective analysis of MRI scans from 24 patients with histologically proven HPNST over a 7-year period.
• Independent assessment of MRI features by two readers, including lesion morphology, nerve involvement, and specific signs (e.g., entering/exiting nerve sign, target sign).
• Evaluation of inter-observer agreement using Cohen's kappa coefficient.

Main Results:

• The study included 24 patients (9 males, 15 females; mean age 50 years).
• Common MRI features included a lobular contour (71%) and ancient/cystic change (38%).
• Classical MRI signs of benign peripheral nerve sheath tumors were infrequently observed.

Conclusions:

• Hybrid peripheral nerve sheath tumors (HPNST) often exhibit a lobular morphology and cystic changes on MRI.
• HPNST less commonly display the characteristic MRI signs associated with benign peripheral nerve sheath tumors.
• This study provides the first analysis of MRI features for histologically proven HPNST.