The patient went on to have a biopsy.

Histology

Sections show fragments of a highly cellular tumor. The tumor is composed of diffuse sheets of markedly atypical cells.  The cells have large, irregularly shaped nuclei with vesicular chromatin and a small nucleolus.  There is some crush-artifact within the specimen.  

Immunohistochemistry

Positive for CD45, CD20 and Pax5.  More than 90% of cells are positive for Bcl-2, and approximately 60% of cells are positive for Bcl-6.  MUM1 is positive in almost all cells.  cMyc stains ~20% of cells.  

The tumor cells are negative for CD10, Cyclin D1, CD30, CD15, EBER-ISH, AE1/AE3, Cam5.2, GFAP, OLIG2, SOX10 and S100.

Ki67 labels approximately 80% of cells.   

Final diagnosis

Intradural intramedullary conus lesion consistent with diffuse large B-cell lymphoma, non-germinal center type (LBCL of immune-privileged site, WHO 2022).

Discussion

Primary CSN lymphoma restricted to the spinal cord is uncommon.