Toxoplasmosis vs lymphoma
Updates to Article Attributes
Toxoplasmosis and lymphoma are frequently differential diagnoses in patients with HIV/AIDS and as treatment is substantially different distinguishing the two is important.
In many instances, the imaging appearance is classic and differentiation is not problematic; however, in 50-80% of cases, the appearances can be very similar 1. Below are helpful distinguishing features.
For a general discussion on each diagnosis, please refer to the individual articles: cerebral toxoplasmosis and primary CNS lymphoma.
Radiographic features
Distribution
Primary CNS lymphoma typically demonstrates subependymal spread, whereas toxoplasmosis tends to be scattered through the basal ganglia and at the corticomedullary junction 1.
HIV lymphoma also is far more frequently a solitary lesion, whereas toxoplasmosis is usually multifocal (86%) 2,3.
Enhancement
On CT and MRI, both entities enhance following administration of contrast. Lymphoma may solidly enhance, whereas toxoplasmosis usually demonstrates ring or nodular enhancement 1,2.
However, in the setting of HIV/AIDS, primary CNS lymphoma may also demonstrate peripheral enhancement. Thus, the pattern of enhancement may not be helpful.
Haemorrhage
Haemorrhage is uncommon in lymphoma, especially prior to treatment, but may be seen occasionally in toxoplasmosis.
MR spectroscopy
- both entities demonstrate increased lactate and lipids, although this tends to be less marked in lymphoma
- lymphoma typically demonstrates marked increase in choline, whereas it is reduced in toxoplasmosis 1,2
- both lesions demonstrate decreased creatine and NAA; however, this finding is variable
Ideally, MR spectroscopy (MRS) should be performed with both long and short TE sequences 1.
MRI perfusion
A decrease in cerebral blood volume (rCBV) centrally within lesions suggests toxoplasmosis, whereas it is increased in lymphoma 1. However, rCBV is reduced in the perilesional oedema of both lesions.
SPECT
Thallium 201 chloride SPECT demonstrates increased uptake in lymphoma because thallium serves as a potassium analogue and is avidly taken up by hypermetabolic tumour cells 6. By contrast, thallium activity is decreased in toxoplasmosis because there is no cellular correlate 2.
Practical points
Features that favour primary CNS lymphoma include:
- single lesion
- subependymal spread
- solid enhancement
- no haemorrhage before treatment
-
Thalliumthallium SPECT positive - MRS: increased choline
- MR perfusion: increased rCBV
Features that favour cerebral toxoplasmosis include:
- multiple lesions
- scattered throughout the basal ganglia and corticomedullary junction
- ring or nodular enhancement
- haemorrhage occasionally occurs mostly in the periphery of the lesion
-
Thalliumthallium SPECT negative - MRS: decreased choline (Cho)
- MR perfusion: decreased rCBV
-<p><strong>Toxoplasmosis and lymphoma</strong> are frequently differential diagnoses in patients with HIV/AIDS and as treatment is substantially different distinguishing the two is important. </p><p>In many instances, the imaging appearance is classic and differentiation is not problematic; however, in 50-80% of cases, the appearances can be very similar <sup>1</sup>. Below are helpful distinguishing features.</p><p>For a general discussion on each diagnosis, please refer to the individual articles: <a title="Cerebral toxoplasmosis" href="/articles/neurotoxoplasmosis">cerebral toxoplasmosis</a> and <a title="Primary CNS lymphoma" href="/articles/primary-cns-lymphoma">primary CNS lymphoma</a>.</p><h4>Radiographic features</h4><h5>Distribution</h5><p>Primary CNS lymphoma typically demonstrates subependymal spread, whereas toxoplasmosis tends to be scattered through the <a href="/articles/basal-ganglia">basal ganglia</a> and at the corticomedullary junction <sup>1</sup>. </p><p>HIV lymphoma also is far more frequently a solitary lesion, whereas toxoplasmosis is usually multifocal (86%) <sup>2,3</sup>.</p><h5>Enhancement</h5><p>On CT and MRI, both entities enhance following administration of contrast. Lymphoma may solidly enhance, whereas toxoplasmosis usually demonstrates <a href="/articles/cerebral-ring-enhancing-lesions">ring</a> or nodular enhancement <sup>1,2</sup>.</p><p>However, in the setting of HIV/AIDS, primary CNS lymphoma may also demonstrate peripheral enhancement. Thus, the pattern of enhancement may not be helpful.</p><h5>Haemorrhage</h5><p>Haemorrhage is uncommon in lymphoma, especially prior to treatment, but may be seen occasionally in toxoplasmosis.</p><h5>MR spectroscopy</h5><ul>- +<p><strong>Toxoplasmosis and lymphoma</strong> are frequently differential diagnoses in patients with HIV/AIDS and as treatment is substantially different distinguishing the two is important. </p><p>In many instances, the imaging appearance is classic and differentiation is not problematic; however, in 50-80% of cases, the appearances can be very similar <sup>1</sup>. Below are helpful distinguishing features.</p><p>For a general discussion on each diagnosis, please refer to the individual articles: <a href="/articles/neurotoxoplasmosis">cerebral toxoplasmosis</a> and <a href="/articles/primary-cns-lymphoma">primary CNS lymphoma</a>.</p><h4>Radiographic features</h4><h5>Distribution</h5><p>Primary CNS lymphoma typically demonstrates subependymal spread, whereas toxoplasmosis tends to be scattered through the <a href="/articles/basal-ganglia">basal ganglia</a> and at the corticomedullary junction <sup>1</sup>. </p><p>HIV lymphoma also is far more frequently a solitary lesion, whereas toxoplasmosis is usually multifocal (86%) <sup>2,3</sup>.</p><h5>Enhancement</h5><p>On CT and MRI, both entities enhance following administration of contrast. Lymphoma may solidly enhance, whereas toxoplasmosis usually demonstrates <a href="/articles/cerebral-ring-enhancing-lesions">ring</a> or nodular enhancement <sup>1,2</sup>.</p><p>However, in the setting of HIV/AIDS, primary CNS lymphoma may also demonstrate peripheral enhancement. Thus, the pattern of enhancement may not be helpful.</p><h5>Haemorrhage</h5><p>Haemorrhage is uncommon in lymphoma, especially prior to treatment, but may be seen occasionally in toxoplasmosis.</p><h5>MR spectroscopy</h5><ul>
-</ul><p>Ideally, <a href="/articles/mr-spectroscopy-1">MR spectroscopy (MRS)</a> should be performed with both long and short TE sequences <sup>1</sup>.</p><h5>MRI perfusion</h5><p>A decrease in <a title="relative cerebral blood volume (rCBV)" href="/articles/cerebral-blood-volume-cbv">cerebral blood volume (rCBV)</a> centrally within lesions suggests toxoplasmosis, whereas it is increased in lymphoma <sup>1</sup>. However, rCBV is reduced in the perilesional oedema of both lesions.</p><h5>SPECT</h5><p><a href="/articles/thallium-201-chloride-1">Thallium 201 chloride</a> SPECT demonstrates increased uptake in lymphoma because thallium serves as a potassium analogue and is avidly taken up by hypermetabolic tumour cells <sup>6</sup>. By contrast, thallium activity is decreased in toxoplasmosis because there is no cellular correlate <sup>2</sup>.</p><h4>Practical points</h4><p>Features that favour <a href="/articles/primary-cns-lymphoma">primary CNS lymphoma</a> include:</p><ul>- +</ul><p>Ideally, <a href="/articles/mr-spectroscopy-1">MR spectroscopy (MRS)</a> should be performed with both long and short TE sequences <sup>1</sup>.</p><h5>MRI perfusion</h5><p>A decrease in <a href="/articles/cerebral-blood-volume-cbv">cerebral blood volume (rCBV)</a> centrally within lesions suggests toxoplasmosis, whereas it is increased in lymphoma <sup>1</sup>. However, rCBV is reduced in the perilesional oedema of both lesions.</p><h5>SPECT</h5><p><a href="/articles/thallium-201-chloride-1">Thallium 201 chloride</a> SPECT demonstrates increased uptake in lymphoma because thallium serves as a potassium analogue and is avidly taken up by hypermetabolic tumour cells <sup>6</sup>. By contrast, thallium activity is decreased in toxoplasmosis because there is no cellular correlate <sup>2</sup>.</p><h4>Practical points</h4><p>Features that favour <a href="/articles/primary-cns-lymphoma">primary CNS lymphoma</a> include:</p><ul>
-<li>Thallium SPECT positive</li>- +<li>thallium SPECT positive</li>
-<li>Thallium SPECT negative</li>- +<li>thallium SPECT negative</li>