Penetration failure and misdiagnosis of stereotactic biopsy caused by the uncommonly firm tissue of a gliomyosarcoma.

Objective and Importance: We report the very rare case of a gliomyosarcoma that caused penetration failure in stereotactic biopsy and therefore led to misdiagnosis. This complication should be considered as a potential reason for diagnostic failure with uncommonly firm tumors in frame-based stereotactic biopsy. Clinical Presentation: An 83-year-old women presented with a 4-week history of right hemiparesis. Computed tomography (CT) demonstrated a left precentral lesion of 1 cm in diameter with moderate contrast uptake and perifocal edema. Intervention: Stereotactic biopsy was performed using the Cosman-Robert-Wells (CRW) system and a side-aspirating biopsy needle. Six tissue samples were taken;, however, histopathologic examination remained non-diagnostic. Because the hemiparesis had worsened, a magnetic resonance tomography (MRT) was taken four weeks later and clearly demonstrated an increase in size of the lesion. Neuronavigation-guided open surgery revealed a very firm, well-delimited tumor that was classified in the pathologic examination as a gliomyosarcoma. Repeated recalculations of the target coordinates, analysis of the CT scan that was taken 4 days after the stereotaxy, and finally, recognition of the extraordinary firmness of this gliomyosarcoma allowed us to presume with certainty that we had not penetrated the lesion with the biopsy cannula, but rather had merely pushed it ahead of the instrument while the tissue samples were taken. Conclusion: The reported case is both unique for its histopathologic diagnosis and for the complication it caused in stereotactic biopsy. The case also supports the implementation of image-guided interventions for diagnostic biopsy, rather than frame-based stereotaxy in the future.