Tissue cells that are never seen in peripheral blood but are often seen in spinal fluid samples are presented in the table below:
| Cells | Causes |
| macrophages | - RBC's in CSF
- viral meningitis
- tubercular meningitis
|
| ependymal | normal - due to shedding of cells that line the ventricles |
| pia arachnoid mesothelial cells (PAM) | normal - due to shedding of cells lining the arachnoid space |
These cells are important because they must be differentiated from tumor cells and blast cells.
