Benign peripheral nerve tumors: Analysis of 89 FNA cases emphasizing diagnostic accuracy and their morphologic spectrum

Abstract

AbstractIntroductionBenign peripheral nerve tumors (BPNTs) are a heterogenous group of soft tissue tumors that include a variety of nerve sheath tumors, granular cell tumor (GCT), and ganglioneuroma. Only a few large studies exist on cytopathology and diagnostic accuracy using fine‐needle aspiration (FNA) biopsy for this set of neoplasms.Materials and methodsBoth surgical and cytopathology files were searched for cases of BPNT. FNA biopsy was performed using standard techniques.ResultsEighty‐nine cases from 88 patients (male:female = 1:1; age range: 16–85 years, mean age, 51 years) met inclusion criteria. FNA sites included extremities (58, 65%), head/neck (14, 16%), deep (9, 10%), and trunk (8, 10%). Aspirates were from primary neoplasms in all but one instance. There were 65 schwannomas, seven neurofibromas, seven perineuriomas, seven GCTs, and three ganglioneuromas/neuromas. Aspirates of schwannoma, GCT, neurofibroma (NF), and perineurioma (PN) were correctly diagnosed in 86%, 100%, 29%, and 0% of cases, respectively. Five tumors (6%) were interpreted as either a specific sarcoma or suspicious for sarcoma. Remaining aspirates were classified as spindle cell neoplasm, salivary gland neoplasm, and nondiagnostic. Cytologic features for schwannoma, NF, PN, and ganglioneuroma showed spindle cell–dominant smears arranged mainly in syncytial clusters. GCT aspirates contained a population of epithelioid cells harboring coarsely granular cytoplasm and bare nuclei. Immunohistochemical (IHC) staining in 55 (62%) cases showed S‐100 expression in 95%.ConclusionFNA biopsy coupled with IHC is reliable in correctly classifying schwannoma and GCT, but less so for NF. Perineurioma can be mistaken for sarcoma.