Adult Primary Extramedullary Spindle Cell Neoplasms of the Spinal Cord: Algorithmic Approach to a Frozen Section Dilemma

Abstract Introduction/Objective Spinal cord lesions can be designated as either (1) intramedullary, located within the spinal cord, or (2) extramedullary, located outside of the spinal cord, with further craterization as intradural and extradural. Neoplasms with a spindle cell phenotype can be challenging to optimally classify at the time of frozen section with immunohistochemistry necessary for optimal classification. This study looks at a spectrum of spinal cord tumors with a significant spindle cell component and offers an algorithmic approach for intraoperative consultation. Methods/Case Report A series of extramedullary spindle cell cases was compiled for comparison and contrast. A PubMed and Google literature search was undertaken. Results (if a Case Study enter NA) A total of 10 cases, age range 33-67, were compiled including meningioma with predominantly spindle cell features (WHO grade 1 and grade 2), solitary fibrous tumor, schwannoma lacking nuclear palisades and Verocay bodies, neurofibroma; malignant peripheral nerve sheath tumor, perineurioma, and spindle cell (tanycytic) ependymoma. During intraoperative consultation, touch preparations and frozen section features often overlapped. Radiologic localization of the neoplasm was essential to effective frozen section diagnosis as some lesions had a distinctly astrocytic phenotype. A general diagnosis was often employed, specifically spindle cell neoplasm with or without high-grade features. A differential diagnosis was provided when characteristic features were identified, including whorls, psammoma bodies, and intranuclear cytoplasmic inclusions favoring meningioma; abundant collagen between cells; nuclear palisades and Verocay bodies suggestive of Schwannoma; abundant extracellular matrix suggestive of neurofibroma; and perivascular pseudorosettes suggestive of extramedullary ependymoma variant. Conclusion This study provides a summary of extramedullary spinal region lesions that overlap with respect to imaging and frozen section characteristics. It emphasizes the need for clinical-radiologic-pathologic correlation on such lesions, the challenges in generating the differential diagnosis prior to histologic evaluation, and the pragmatism to rendering a diagnosis of spindle cell neoplasm with a differential diagnosis at frozen section.