This was an 18-year-old female who was found to have mass in foramen magnum, impinging on the cervicomedullary junction. Neurosurgical intervention followed shortly.
It's not a difficult diagnosis to make. The diagnosis hinges upon recognizing a focal yet interesting feature of the neoplastic cells, and remembering why the "mystery immunostain"would use a red chromogen.
|Sagittal T1, post-gadolinium|
|H&E, intermediate magnification|
|H&E, high magnification|