Ccghc

1. Journal:Typical and Atypical CT
and MRI appearances of Primary
CNS lymphomas

2. Primary central nervous system (CNS)
lymphoma
• refers to isolated involvement of the craniospinal axis in the
absence of primary tumor elsewhere in the body.
• Once considered a rare occurrence, primary lymphomatous disease
of the CNS is now encountered frequently, in both
immunocompetent and immunocompromised patients.
• HIV infection and AIDS are the leading risk factors and diagnosis of
primary CNS lymphoma in a patient with HIV is an independent
criterion for AIDS.
• Congenital causes of immunodeficiency (e.g., Wiskott-Aldrich
syndrome, IgA deficiency, and X-linked lymphoproliferative
syndrome) and acquired causes, including an immunosuppressive
regimen after organ transplantation, are also associated with
greater risk for primary lymphoma of the CNS

3. • Primary CNS lymphoma may arise from different
parts of the brain, with deep hemispheric
periventricular white matter being the most
common; corpus callosum, cerebellum, orbits,
and cranial nerves may also harbor the tumor
• After the diagnosis is made, an examination is
done that includes MR imaging of the
craniospinal tract; cerebrospinal fluid and bone
marrow examinations; and screening for primary
tumor in the eye, chest, and abdomen

4. • The presenting symptoms in primary CNS
lymphoma vary depending on the location of the
masses and the immune status of the patient.
• Primary CNS lymphoma in immunocompetent
patients tends to present with a large solitary
hemispheric mass.
• HIV-positive patients often present with an acute
change in mental status and an encephalopathy-
like picture, likely related to combined effects
from other concomitant infections and the side
effects of antiretroviral drugs

5. • The traditional method of administering 2 weeks of
empiric antitoxoplasmosis treatment to distinguish
between primary CNS lymphoma and toxoplasmosis,
the most common cause of solitary or multiple brain
masses in an HIV patient, is not warranted in patients
with negative serology findings
for Toxoplasma organisms.
• Because of the rapid course of primary lymphoma, a
delay in whole brain irradiation and chemotherapy
markedly decreases the effectiveness of the treatment
and survival. Therefore, early diagnosis is critical.

6. • Systemic lymphoma, on the other hand, may also present
with neurologic symptoms in one third of patients
sometime during the course of the disease.
• Imaging studies are often helpful to distinguish primary
CNS lymphoma from systemic lymphoma; the latter
typically invades dural and leptomeningeal coverings of the
brain. A high-attenuation lesion on CT and a periventricular
T2 low-signal-intensity mass with ependymal seeding on
MR imaging favor the diagnosis of primary lymphoma.
• CT, MR imaging, and 201Tl scintigraphy remain the mainstay
in diagnostic imaging workup of primary CNS lymphoma

7. • Typical Appearance in Immunocompetent PatientsIn patients with
normal immunity, lymphoma classically presents as a solitary
homogeneously enhancing mass [5,6,7] (Fig. 1A,1B,1C,1D). Internal
calcification is unusual in CNS lymphomas unless the patient has
undergone prior chemotherapy or radiation treatment. In most
patients, MR imaging reveals intermediate- to low-signal-intensity
tumor on T1-weighted images and either isointense or hypointense
signal relative to the gray matter on T2-weighted images (Fig. 1C).
Classic findings of a space-occupying lesion, including mass effect
and surrounding vasogenic edema, are seen on imaging studies [3].
After the infusion of paramagnetic contrast material, intense
homogeneous enhancement (74%) of a solitary mass is the
hallmark of primary CNS lymphoma in immunocompetent patients
(Fig. 1D).

11. • Unenhanced CT typically shows a high-density
(70%) lesion in a central hemispheric location,
which often reaches or crosses the midline.
• Highly packed abnormal cells are thought to
be responsible for the increased attenuation.
Hemorrhage within the tumor is rarely seen,
although it is more common in lymphoma
associated with AIDS.

14. • ypical Appearance in HIV PatientsIn more
than half (55%) the patients, a cerebral mass
is detected in a supratentorial parenchymal
location with frequent involvement of the
corpus callosum, basal ganglia, and other
deep cerebral nuclei

16. • Contrast enhancement is variable, commonly
of an inhomogeneous or bizarre pattern.
Solitary ringlike enhancement is more likely
seen in this group

18. • When necrosis develops in the tumor (64%),
the periphery still maintains an isointense
signal and the center becomes hyperintense.
Multiple lesions may be seen in as many as
50% of patients

20. • Extension along the Virchow-Robin spaces is a
well-known feature of primary lymphoma.
Periventricular lesions frequently invade the
ventricular surface, causing ependymal
seeding (38%)
• However, meningeal enhancement is
surprisingly not frequent.

22. • Atypical CNS LymphomasAlthough
lymphomas are usually hyperdense, they may
also show isodensity or even hypodensity on
CT. In the setting of a periventricular low-
density lesion, lymphoma may easily be
misdiagnosed as chronic small vessel ischemia
or encephalomalacia

24. • Diffusely infiltrative lymphomas may not
exhibit parenchymal enhancement at all
(Fig. 8A,8B,8C).

26. • The tumor sometimes may show mild
hyperintensity on T1-weighted images. Dense
cellularity and high nucleus-to-cytoplasm ratio
of the tumor accounts for the isointense or
slightly hypointense signal seen on T2-
weighted sequences. Hemorrhage in the
tumor also results in low signal intensity on
gradient-echo images because of magnetic
susceptibility.

28. • Atypical LocationsA rare primary lymphoma
of the pineal gland appears similar to a
primary neoplasm of pineal origin

30. • Cranial nerves, brainstem, cavernous sinus, or
tuber cinereum may have lymphomatous
involvement.
• In general, primary CNS lymphoma in unusual
locations is more common in patients with
AIDS.

34. Conclusion
• In contrast to the large high-attenuation mass in a hemispheric or
central location that is seen in immunocompetent patients, primary
CNS lymphoma in HIV patients may present as a single lesion or as
multiple lesions in deep portions of the brain. A necrotic core within
the tumor and peculiar enhancement in an unusual location are
also more likely because of HIV-associated lymphoma.
Subependymal enhancement should be actively sought on imaging
studies as a potential clue to lymphomatous involvement. Presence
of a T2-hypointense component resulting from increased cellularity
should also be noted. These imaging features may allow earlier
detection of primary CNS lymphoma and facilitate optimal
treatment.