1. The Multifaceted Imaging Appearance of Primary CNS Lymphoma1
The Multifaceted Imaging Appearance of Primary CNS Lymphoma
Christopher Starr, Ashesh Thaker, Soonmee Cha
UCSF Dept. of Radiology & Biomedical Imaging
Control #1173
eEdE#: eEdE - 89

2. 2
Disclosures
The authors have no disclosure or conflict of interest to disclose.

3. 3
Main message
Primary CNS lymphoma can have a range of imaging appearances that mimick benign and malignant brain lesions. It is essential to differentiate this rare entity from other brain lesions for appropriate clinical prognostication and treatment.

4. Main messages of this presentation4
1. Primary CNS lymphoma is rare and can occur in immunocompetent patients
2. High index of suspicion is a must
3. This entity can take on a range of imaging appearances

5. Cases 5

6. A B Which is primary CNS lymphoma? 6 Axial T1 post-gad+
Axial T1 post-gad +

7. A B Which is primary CNS lymphoma? 7 Axial T1 post-gad+
Axial T1 post-gad +

8. A B Which is primary CNS lymphoma? 8 Axial T1 post-gad+
Axial T1 post-gad +

9. 2. Homogeneous enhancement
Typical features of CNS Lymphoma 9
1. Hypointense on T2
2. Homogeneous enhancement
3. Hyperdense on CT
4. Hypointense on ADC
5. Intra-axial location

10. Hypointense on T2 10 - CNS lymphomas are small round blue cell tumors.
- This feature makes the tumor highly cellular.
- Dark T2 signal is thought to be due to high cellularity.
Very hypointense on T2
Axial T2 +

11. Homogeneous enhancement11
CNS lymphoma enhances homogeneously and avidly.
However, enhancement can be heterogeneous in immunocompromised patients.
Some lymphomas do not enhance much at all, making the diagnosis a difficult one to make.
Homogeneous enhancement
Axial T1 post gad +

12. Hyperdense on CT 12
Hyperdensity on CT is due to dense celluarity of CNS lymphomas.
This feature is unique to CNS lymphomas. Other brain tumors are generally not this hyperdense.
Beware, don’t confuse hyperdensity with hemorrhage!
Hyperdense
Axial noncon CT +

13. Reduced on ADC 13
Because of their high cellularity, CNS lymphomas have restricted diffusion and are hypointense on ADC.
This feature can be very helpful when trying to distinguish lymphomas from other brain tumors which are generally not as profoundly reduced on ADC.
Very hypointense on ADC
Axial ADC +

14. Intra-axial in location(often periventricular)14
Axial T1post-gad +
Axial T1 post gad +
Primary CNS lymphomas are generally intra-axial and often periventricular. This is in contrast to metastatic lymphomas which are often leptomeningeal or dural based. However, primary CNS lymphomas can occur anywhere in the brain.

15. CNS lymphomas like periventricular location15
CNS lymphomas like periventricular location
Axial T1 post con +
Coronal T1 post con +
Axial T2 FLAIR +
Axial ADC +
- CNS lymphomas are one of the brain lesions that like to involve the corpus callosum. This case demonstrate involvement of the splenium of the corpus callosum. Other entities that likes corpus callosum are GBM and demyelinating lesions. This splenial mass demonstrates characteristic homogenous enhancement, T2 hypointensity, and reduced ADC.

16. 16
However, CNS lymphomas can take on a variety of imaging appearances and occur in many atypical locations.

17. Some look like glioblastoma multiforme17
Some look like glioblastoma multiforme
At first glance, this avidly enhancing and centrally necrotic mass may make one suspect high grade glioma.
Axial T1 post-gad +
Axial T1 pre-gad +

18. 18
Look at all sequences!
Highly compacted and cellular CNS lymphomas demonstrate very reduced ADC and hypointensity on T2 FLAIR.
These features are not usually seen in other brain tumors.
Axial ADC +
Axial T2 FLAIR +

19. Remember to also look at your CT!19
Remember to also look at your CT!
Axial ADC +
Axial T2 FLAIR +
Axial noncon CT +
Hyperdensity best appreciated on CT is characteristics of CNS lymphomas.
This feature is usually not seen in other gliomas.

20. 20
Another GBM mimic
Remember CNS lymphomas in immunocompromised patients can be very heterogeneous and necrotic, mimicking GBM on post-contrast images.
Axial T1 post-gad +
Axial T2 +
Axial ADC +
BUT… Look at how dark it is on T2 and ADC. This should make you suspect CNS lymphoma.

21. CNS lymphomas can also spread along the ependyma21
CNS lymphomas can also spread along the ependyma +
Axial T1 post con +
Axial ADC +
Axial noncon CT +
Look at how this periventricular CNS lymphomas can spread along the ependyma.
This mass demonstrates the characteristic appearance of reduced ADC and hyperdensity on CT.

22. Evolution of subependymal spread in a different patient22
Evolution of subependymal spread in a different patient
This mass mimicks a colloid cyst!
Axial T1 pre +
Axial T1 post con +
Axial DWI +
Axial ADC +
This patient presents with multiple periventricular masses with characteristic appearance of primary CNS lymphoma.
Watch as these periventricular masses start to spread along the ependyma on subsequent follow-up study.

23. Subependymal and periventricular spread of lymphoma23
Subependymal and periventricular spread of lymphoma
8 weeks later
Notice new enhancement along the left frontal horn with corresponding reduced ADC consistent with spread.
Axial post con +
Axial post con +
The masses along the midline and along the atria of left lateral ventricle have also increased in size.
Axial ADC +
Axial ADC +

24. Subependymal and periventricular spread of lymphoma24
Subependymal and periventricular spread of lymphoma
12 weeks later
Further progression of subependymal and periventricular spread by the lymphomas on the higher slices.
Axial post con +
Axial post con +
Axial ADC +
Axial ADC +
Higher slices

25. Not all lymphomas are in typical locations25
Not all lymphomas are in typical locations
At first glance, this enhancing lesion at gray-white junction could have easily been misinterpreted as a solitary brain metastasis.
Axial T1 post con +

26. Look at all of your sequences!26
Look at all of your sequences! +
Axial ADC
Axial T1 post con +
Axial T2 + +
Axial DWI +
This lesion is mildly hypointense on T2 but it is very reduced on ADC. This should make you include CNS lymphoma in your differential diagnoses.

27. CNS lymphoma can also be multifocal27
CNS lymphoma can also be multifocal
Patient 1
Axial T1 post con +
Axial T2 FLAIR +
Axial T1 post CON +
Axial T2 FLAIR +
This multifocal CNS lymphoma demonstrates characteristic hypointensity on T2 FLAIR. Several of these lesions are periventricular and homogeneously enhancing.

28. Another multifocal case mimicking brain metastases28
Another multifocal case mimicking brain metastases
Coronal post T1 +
Coronal post T1 +
Axial post T1 +
Axial post T1 +
These post contrast MRI images show what appears to be multiple brain metastases.

29. Look at all of your sequences!29
Look at all of your sequences!
Axial T2 FLAIR +
Axial T2 FLAIR +
Axial ADC +
Axial ADC +
However, these lesions are T2 FLAIR hypointense and reduced on ADC, again raising suspicion for CNS lymphomas.

30. 30
The following cases are for show-and-tell and meant to show various atypical appearances that CNS lymphomas can take.

31. Some mimick leptomeningeal inflammatory disease31
Some mimick leptomeningeal inflammatory disease
Sagittal post T1 +
Axial T1 post +
- Multiple areas of leptomeningeal enhancement suggesting possible neurosarcoidosis, tuberculosis, or leptomeningeal carcinomatosis.

32. Look carefully! Rare presentation and location32
Look carefully! Rare presentation and location
CNS lymphoma can rarely occur in the posterior fossa.
Sagittal post T1 +
Axial T1 post +
Sagittal T2 FLAIR +
Axial ADC +
VERY DARK ON ADC
- It can be very difficult to make the diagnosis. Careful examination shows that this mass is reduced on ADC. This should prompt you to include CNS lymphoma in your differentials.

33. How about this one that mimicks a sellar/suprasellar mass33
How about this one that mimicks a sellar/suprasellar mass
Coronal T1 post-gad +
Axial T1 post-gad +
Sagittal post-gad T1 +

34. How about this one that mimics sella/suprasellar mass34
How about this one that mimics sella/suprasellar mass
Coronal T1 post-gad +
Axial T1 post-gad +
Sagittal post-gad T1 +
Coronal T2 FLAIR +
Hypointense on T2 FLAIR
This mass mimicks a pituitary macroadenoma. Careful examination shows that the mass is actually T2 hypointense. Although it is difficult to make the diagnosis, CNS lymphoma should also be included in the differentials in the appropriate clinical setting.

35. Some can mimick brainstem gliomas35
Some can mimick brainstem gliomas
Patient 1
Axial T2 FLAIR +
Axial T1 post con +
Axial T1 post con +
Patient 2
Axial T2 FLAIR +
Axial T1 post con +
Axial T1 post con +

36. Atypical appearances of CNS lymphoma36
Atypical appearances of CNS lymphoma
- This case mimicks bilateral basal ganglia hemorrhage, hemorrhagic venous infarcts, viral encephalitis, or toxic metabolic causes on CT.
Axial noncon CT +

37. Atypical appearances of CNS lymphoma37
Atypical appearances of CNS lymphoma
Notice that this hyperdensity is not as hyperdense as acute hemorrhage.
Enhancing
Dark on T2 FLAIR +
Axial noncon CT +
Axial T1 post con +
Coronal T1 post con +
Coronal T2 FLAIR +
- Careful observation of all of the imaging modalities and sequences demonstrate enhancement and T2 hypointensity of the masses. These features are not seen with hemorrhage or toxic/metabolic diseases. This should make you suspect primary CNS lymphoma.

38. CNS lymphoma mimicking an extra-axial mass38
CNS lymphoma mimicking an extra-axial mass
Coronal T1 post con +
Axial T1 post con +
This avidly enhancing mass mimicks a parafalcine meningioma.

39. CNS lymphoma mimicking a meningioma39
CNS lymphoma mimicking a meningioma
Dark on T2 FLAIR
Coronal T1 post con +
Axial T1 post con +
Coronal T2 FLAIR +
- This marked T2 hypointensity is not seen in meningioma but typical for CNS lymphoma.

40. Another CNS lymphoma mimicking an extra-axial mass40
Another CNS lymphoma mimicking an extra-axial mass
Axial T1 post con +
Coronal T1 post con +
Axial T2 +
Axial T2 FLAIR +
- This centrally necrotic and heterogeneously enhancing mass is CNS lymphoma but mimicks an aggressive extra-axial mass with extension beyond the calvarium.

41. Atypical location of primary CNS lymphoma41
Atypical location of primary CNS lymphoma
Axial T1 post con +
Coronal T1 post con +
Axial DWI +
Axial T2 FLAIR +
- CNS lymphoma is generally located in the supratentorial parenchyma. This enhancing posterior fossa CNS lymphoma is in an atypical location.

42. This one mimicks a pineal and suprasellar mass42
This one mimicks a pineal and suprasellar mass
Coronal T1 post +
Axial T1 post +
Axial T1 post +
Axial T1 post +

43. 2. Homogeneous enhancement
Summary of 5 key features 43
1. Hypointense on T2
2. Homogeneous enhancement
3. Hyperdense on CT
4. Hypointense on ADC
5. Intra-axial location

44. Cases 44

45. A B Which is primary CNS lymphoma? 45 Axial T1 post-gad+
Axial T1 post-gad +

46. A B Additional images 46 + + + + + + + Axial noncon CT Axial T2 FLAIR
Axial ADC +
Axial T2 + A
Axial noncon CT +
Coronal T2 +
Coronal T1 post con + B

47. Additional images 47
Axial noncon CT +
Axial T2 FLAIR +
Axial ADC +
Axial T2 + A
This mass is hyperdense on CT, hypointense on T2, and reduced on ADC. It is also periventricular in location. These findings are very suggestive of primary CNS lymphoma.

48. A B Which is primary CNS lymphoma? 48 Axial T1 post-gad+
Axial T1 post-gad +

49. A B Additional sequences 49 + + + + + + + + Coronal T2 FLAIR Axial ADC
Axial DWI +
Axial T1 post con + A
Axial T1 post-gad +
Axial ADC +
Axial DWI +
Axial T2 FLAIR + B

50. B Additional sequences 50
This lesion mimicks an active demyelinating lesion with a leading edge of enhancement and reduced diffusion. Careful examination shows that the apparent leading edge is actually markedly T2 hypointense. This lesion was a primary CNS lymphoma.
Axial T1 post-gad +
Axial ADC +
Axial DWI +
Axial T2 FLAIR + B

51. A B Which is primary CNS lymphoma? 51 Axial T1 post-gad+
Axial T1 post-gad +

52. A B Additional sequences 52 + + + + + + Axial T1 Post-gad Axial ADC
Axial T2 FLAIR + A
Coronal T1 post con +
Axial ADC +
Axial T1 post-gad + B

53. A Additional sequences 53
Axial T1 Post-gad +
Axial ADC +
Axial T2 FLAIR + A
Although this lesion mimicks brain metastasis, it is markedly reduced on ADC and T2 hypointense. Also, it has an additional site of involvement in the splenium of the corpus callosum. This makes CNS lymphoma a more likely diagnosis.

54. References 54
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