• Clinical History
• Light Microscopy
• Electron Microscopy
• Diagnosis and Comments
• Readers Feedback

Diagnosis: Ependymoma – Thoracic spinal cord

Readers Feedback:

From: Joe Harb harbj@post.its.mcw.edu

To: "Dardick and Hewan-Lowe" <khewanl@zappa.ultrakohl.com>

Subject: Ependymoma - Thoracic Spinal Cord

------------------------------------------

I think that whenever you encounter a moderately cellular neural neoplasm, you need to consider EM in the workup. If the ependymal features are as prominent as they were in this case, particularly the presence of microlumina with associated microvilli and cilia, the distinction from astrocytoma is convincing.

However, all cases are not the same, and there can be less distinctive features present in this type of tumor, and this can make the distinction difficult. For example, sometimes there are not clearly developed microlumina, but cilia can be seen within the cells. These are usually within invaginations of the cell and cut so they appear to be within the cytoplasm. Careful study, however, will usually show a double membrane, with the clear space between the membranes representing the extracellular space. Also, if the cilia or microvilli are not numerous, you may only see a small part of either structure in the section plane, so you have to be able to recognize the features even if the section reveals a very small part of the structure.

Another feature to look for is the basement membrane, but I consider it the fourth item on the list of four features I want to find after elongate junctional complexes, microlumina with associated microvilli, and cilia. I would not consider the presence of the basement membrane alone as a feature indicating ependymal differentiation, or as a distinquishing feature from astrocytoma, because some rare astrocytomas do have basement membranes. They can have junctional complexes, too, and of course, can contain prominent glial filaments, and rarely, dense core granules.