Primary central nervous system lymphoma (PCNSL) refers to lymphoma isolated to the brain and spinal cord. Imaging plays an important role in diagnosis. On CT, PCNSL typically appears as a hyperdense, solitary mass without necrosis or hemorrhage. On MRI, it has intermediate-low T1 signal, iso-hypointense T2 signal, and homogeneous enhancement. Location is commonly the supratentorial white matter. In immunocompromised patients, PCNSL can appear atypical with multiple lesions, necrosis, and heterogeneous enhancement. Advanced techniques like perfusion MRI and PET can aid in differentiating PCNSL from other tumors like glioblastoma and metastasis.

1. Radiological imaging of
Primary CNS Lymphoma.
Dr/ ABD ALLAH NAZEER. MD.

2. Primary CNS Lymphoma (PCNSL) refers to
the isolated involvement of the craniospinal axis in the
absence of primary tumor elsewhere in the body.
Facts about Primary CNS lymphoma.
1)1%-5% of all brain tumors.
2)1% of all Non Hodgkin's Lymphoma (NHLs).
3)Incidence increasing in immunocompetent patients.
4)Most are Diffuse Large B-cell Lymphoma (DLBCLs)
5)Hodgkin's - 0.5%.
6)Metastatic CNS lymphoma, B-cell type - 5-9%.
7)Primary T-cell lymphoma of the CNS- CSF usually negative.
Etiology: Precise etiology not known as CNS devoid of
lymphatics, lymphocytes

3. Risk increases in patients with.
1)Autoimmune diseases like Sjögren
syndrome, and systemic lupus erythematosus.
2)Viruses: Epstein-Barr virus (10-15%) and
HIV/AIDS (Patients on HAART in later stage of
disease).
3)Congenital immunodeficiency syndromes.
4)Severe immunosuppression (chemotherapy,
long-term steroids).

4. Imaging findings OR Procedure details.
Typical Appearance in Immunocompetent Patients:
Imaging Characteristics:
1)Usually solitary mass( 40-60%) hyperdense on CT with no
hemorrhage, necrosis or calcification.
2)Intermediate to low signal intensity on T1W images.
3)Isointense or hypointense signal relative to the gray matter on
T2W images.
4)Restricted Diffusion with intense homogeneous post-contrast
enhancement .
Location:
Supratentorial frontoparietal white matter, Periventricular regions ,
Deep gray nuclei and Corpus callosum (Common)
Posterior fossa, Hypothalamus, Infundibulum and Pituitary gland
(Uncommon).
Primary dura-based lymphomas (Rare).

5. Unsual Findings, especially in Immuno-compromised Patients:
Multiplicity .
Hemorrhage.
Lack of enhancement.
Necrosis.
Calcification.
Atypical location.
Age Group.
IMMUNOCOMPETENT IMMUNOCOMPROMISED
Age (Mean) 60 yrs. 30 yrs.
Multiple lesions 30-50%. 63-81%.
Necrotic change Rare. Common.
CT
Density. Hyperdense. Hyperdense.
Enhancement . Homogenous Heterogeneous.
MR Imaging.
T1 signal . Iso-Hypo. Iso-Hypo.
T2 signal . Iso- Hypo. Iso-Hypo.
Enhancement. Homogenous. Heterogeneous.

6. PCNSL - Advanced techniques.
Perfusion: Low relative Cerebral Blood Volume (rCBV).
MR Spectroscopy (MRS) : High Cho/Cr ratio, low NAA, high
lipid pea.
PET: Increased uptake of DG/methionine.
Primary CNS lymphoma subtypes.
1) Intravascular(Angiocentric)lymphoma .
Small/medium-sized vessels filled with tumor. Multiple
T2/FLAIR hyperintensities with linear/punctate enhancement
oriented along perivascular spaces.
2) Lymphomatosis cerebri .
Middle-aged or elderly with rapidly progressive dementia and
ataxia.
Patchy and confluent T2/FLAIR hyperintensities with no
enhancement.

7. Typical Appearance in Immunocompetent Patients(B-Cell Type).
Imaging Characteristics:
1)Usually solitary mass( 40-60%) hyperdense on CT with no
hemorrhage, necrosis or calcification.
2)Intermediate to low signal intensity on T1W images.
3)Isointense or hypointense signal relative to the gray matter on
T2W images.
4)Restricted Diffusion with intense homogeneous post-contrast
enhancement.
Location:
Supratentorial frontoparietal white matter, Periventricular regions ,
Deep gray nuclei and Corpus callosum (Common).
Posterior fossa, Hypothalamus , Infundibulum and Pituitary gland
(Uncommon)
Primary dura-based lymphomas(Rare).
Imaging findings.

20. Multiplicity of Primary CNS Lymphoma(immunocompromized)

24. Atypical Appearance and Location of Lymphoma(Follow-up Study)

40. Differential Diagnosis:
1)Glioblastoma multiforme (GBM):Relatively homogeneous and
strong enhancement in immunocompetent patients with PCNSL
while peripheral irregular ring with central nonenhancing necrosis
is more typical of GBM. Hemorrhage and necrosis are rare in PCNSL.
2)Metastasis: Second most common differential diagnosis of PCNSL
especially hyperdense metastasis from Renal Cell Carcinoma or
Mucinous primary. Metastasis are hyperperfused with high rCBV
3)High Grade Glioma: Hyperperfused with heterogeneous
enhancement.
4)Progressive multifocal leukoencephalopathy (PML):
a) Large multifocal asymmetric predominantly white matter non-
enhancing lesions extending to involve the subcortical U-fibers
b) Absent mass effect with restricted diffusion along the advancing
edge of demyelination.
c) Increase Cho levels with increase in mI suggestive of PML.

41. 5)Toxoplasmosis: especially in Immumocompromised patients.
a)Solitary ring-enhancing lesion in an HIV/AIDS patient, most
often lymphoma.
b)Multiple lesions are characteristic of toxoplasmosis.
c)Toxoplasmosis is hypometabolic on PET.
d)MRS: Important lipid peak. NAA. Cho, Cr & mI nearly absent.
6) Immune reconstitution inflammatory syndrome( IRIS):
Immune reconstitution inflammatory syndrome (IRIS) occur
days to weeks after commencing patient on highly active
anti-retroviral therapy (HAART) Bizarre-looking parenchymal
masses and progressively enlarging enhancing lesions are
typical of IRIS.
7)Lymphomatoid granulomatosis and PTLD in transplant
patients.

44. Conclusion.
1)Once a rare neoplasm; PCNSL is now amongst
the common CNS tumors.
2) Increasing incidence in immunocompetent
individuals noted.
3) Contrast enhanced MR with diffusion weighted
is modality of choice.
4) Advanced imaging techniques have a definite
role as problem solving tool in PCNLS,
especially in cases with unusual imaging
characteristics and location.

45. Thank You.