Cytologic Findings of Fine Needle Aspiration Biopsy of 23 Schwannomas

Abstract

In an attempt to better define the cytologic characteristics of schwannomas, we have reviewed aspirates and corresponding histologic sections from 23 schwannomas. Of this number, the original cytologic diagnoses were: schwannoma in 14 cases (61%), benign soft tissue tumor in 2 cases (9%), and insufficient specimen in 7 cases (30%). The cytologic findings common to all cases of schwannoma included fragments of tightly cohesive fascicles with variable cellularity and corresponding Antoni type A area. The Antoni type B area, consisting of scattered spindle cells and some histiocytes and lymphocytes against a myxoid background, was seen in 14 cases. Fibrillary stroma was seen in 12 cases. The tumor cells had spindle- or ovalshaped nuclei, with pointed ends and indistinct cell borders. Nuclear palisading was seen in 10 cases, and distinctive Verocay bodies were seen in 5 cases. In ancient schwannomas, there were no Verocay bodies. Most schwannomas have distinct cytomorphologic features that allow correct diagnosis. The major problem with fine needle aspiration cytology of these tumors is the high frequency of poor cellularity, particularly in lesions with cystic degeneration. Of 7 cases with insufficient specimen, 4 showed marked cystic changes and 1 showed marked hyaline changes on histologic sections. In conclusion, we believe that if cytopathologist reminds the situation such as cystic degeneration or hyaline degeneration, the correct diagnosis of the schwannoma will be easily made.