A 42-year-old man with a past medical history significant for neurofibromatosis type 2 (NF2) with multiple resections of meningiomas, perineuriomas, schwannomas, and a spinal ependymoma. Spine MRI now shows an expansile intramedullary mass (1.5 x 1.2 x 1.2 cm) centered at C4 with surrounding edema. The lesion has steadily increased in size. Upon resection, the histologic findings are seen in the images.
The correct answer is ...
Mixed schwannoma and spinal ependymoma.
The tumor showed two distinct components. The first component is consistent with a low-grade ependymoma and is highlighted by GFAP. The tumor shows inconspicuous mitotic activity and no microvascular proliferation or necrosis, supporting a CNS grade 2 designation.
The second component is consistent with a schwannoma, which is highlighted by SOX-10. This component was also positive for S100 with Collagen IV highlighting continuous basement membrane.
Overall, the findings are in keeping with a collision tumor representing two distinct neoplasms, both frequently seen in patients with NF 2.
Spinal ependymomas are frequently seen in patients with NF2. A component of this tumor is consistent with an ependymoma. This is supported by histology showing perivascular pseudorosettes, uniform ovoid nuclei, positive GFAP, and negative OLIG2 immunohistochemistry. The second component of this tumor does not fit this morphology or staining pattern, leaving the possibility of a mixed tumor representing an ependymoma and an additional distinct neoplasm.
Schwannomas are associated with NF2. A component of the tumor is consistent with a schwannoma. This is supported by histology showing alternating hypercellular (Antoni A) and hypocellular (Antoni B) areas, palisading nuclei (Verocay bodies), and highlighted by a positive S-100, SOX-10, and Collagen IV immunohistochemistry stain. The other component of this tumor does not fit this morphology or staining pattern, leaving the possibility of a mixed tumor representing an ependymoma and an additional distinct neoplasm.
Although meningiomas can be located throughout the CNS and are associated with NF2, the histology and immunohistochemical staining pattern of this case does not fit that of a meningioma. Meningiomas are negative for both GFAP and SOX-10 and typically express progesterone receptor, SSTR2, and EMA.
Rachel Horton, D.O.
Resident, Anatomic and Clinical Pathology
Rachael Vaubel, M.D, Ph.D.
Senior Associate Consultant, Anatomic Pathology
Assistant Professor of Laboratory Medicine and Pathology
Mayo Clinic College of Medicine and Science