Percutaneous needle biopsy diagnosis of benign neurogenic neoplasms

Preoperative diagnosis of benign neurogenic neoplasms (BNNs) provides useful information in guiding management. To assess the effectiveness of fine-needle aspiration (FNA) and needle core biopsy (NCB) in diagnosing schwannomas and neurofibromas, 40 percutaneous biopsies interpreted as BNNs or obtained from lesions subsequently shown by excision to be BNNs were reviewed. The 13 aspirates diagnostic of BNN revealed spindle cells arranged haphazardly in irregular tissue fragments and in parallel as elongated ropy fascicles, with a myxoid to fibrillary background. The nuclei were buckled, often with intranuclear cytoplasmic inclusions. Four lesions showed nuclear pleomorphism without mitoses. Of 19 schwannomas evaluated by FNA, four (21%) were diagnosed as schwannomas and seven (37%) as BNNs. Ten neurofibromas were aspirated, revealing two (20%) BNNs. Of seven nondiagnostic FNAs accompanied by NCB, three (43%) indicated a BNN. The sensitivities of FNA, NCB, and both modalities in diagnosing BNNs were 43,60, and 71%, respectively. For the 16 FNAs showing features of BNNs, subsequent excisions revealed 11 schwannomas, two neurofibromas, one neurogenic sarcoma, one fibromyxoid neoplasm of uncertain malignant potential, and one unclassified low-grade myxoid sarcoma. FNA can be effective in diagnosing BNNs. If collagenous or myxoid lesions yield paucicellular nondiagnostic aspirates, NCB is helpful. Lowgrade sarcoma and neurofibromatous areas of neurogenic sarcoma may be misinterpreted as BNNs by percutaneous biopsy. BNNs may show nuclear pleomorphism without mitotic activity, and should not be mistaken for sarcoma.