Cervical schwannoma with intranuclear vacuoles by fine-needle sampling without aspiration

Cytohistologic correlations in schwannomas (neurilemmomas), including "ancient," cellular, and epithelioid variants

Schwannoma accounts for one of the most common benign mesenchymal neoplasms of soft tissues. Although it is well defined in the cytology literature, particular histologic subtypes such as "ancient," cellular and epithelioid variants could be a source of diagnostic difficulties. We have reviewed cytology aspirates and corresponding histologic sections from 34 schwannomas diagnosed at Institut Curie. Histologically, 24 cases were classic, 5 were "ancient," 4 were cellular, and 1 was epithelioid schwannomas. No example of melanotic schwannoma was recorded. Original cytologic diagnosis was schwannoma in 13 (38.2%) cases, benign soft tissue tumor in 11 (32.4%), pleomorphic adenoma in 2 (6%) cases, angioma in 1 (2.9%) case, nodular fasciitis in 1 (2.9%) case, suspicious in 3 (8.8%) cases, and not satisfactory in 3 (8.8%) cases. There were no major differences between classical, "ancient," cellular, and epithelioid variants on cytology smears. Myxoid stroma, mast cells, and intranuclear inclusions were limited to classical subtype. Similarly, cyto-nuclear atypia was more frequent in classical subtype than in other subtypes. Schwannoma should be differentiated from well-differentiated malignant peripheral nerve sheath tumor, neurofibroma, and pleomorphic adenoma, in the last instance particularly for head and neck lesions.

Difficulties in the fine needle aspiration (FNA) diagnosis of schwannoma

The results of nine FNAs of eight histologically proven schwannomas are presented. In only one of the aspirates was a diagnosis of schwannoma made; three additional cases were diagnosed as 'spindle cell neoplasm'. Two of the cases were considered to be non-diagnostic due to hypocellularity, while two cases containing cellular material raised the differential diagnosis of granulation tissue and granulomatous inflammation due to the presence of epithelioid cells and an inflammatory infiltrate, and are illustrated here. The remaining FNA was felt suggestive of branchial cleft cyst due to the presence of only cystic fluid in a neck mass. We observe that: (i) the acquisition of an adequate, representative specimen via FNA is often difficult in schwannoma, and (ii) diagnostic difficulties may be encountered in cases in which cellular material is obtained.

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.

Fine-needle aspiration cytology of malignant nerve sheath tumors

Precise preoperative diagnosis of three malignant nerve sheath tumors (MNST) was based on their remarkably uniform and highly characteristic cytologic appearance. The differential diagnosis with benign nerve sheath tumors and other spindle cell sarcomas is addressed, and the possibility of achieving confident diagnosis on cytologic material from at least some soft-tissue sarcomas is confirmed.