British Journal of Radiology (2003) 76, 145-146
© 2003 British Institute of Radiology
doi: 10.1259/bjr/32821410
A young man with a lump on the head
I T Moorthy, MBBS, MRCP, FRCR and
J B Bingham, MSc, FRCP, FRCR
Radiological Sciences, Guy's Hospital, 3rd Floor Guy's Tower, St Thomas Street, London SE1 9RT, UK
Correspondence: Dr Ima Moorthy, 47 Alwyne Road, Wimbledon SW19 7AE, UK
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Case history
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A 27-year-old Caucasian male patient presented with a 4 week history of unsteadiness of gait, bilateral leg weakness, gradual loss of bladder and rectal continence and decreased visual acuity. The patient had been treated for a presumed liver abscess 2 months previously. The patient had lost 15 kg in weight over 6 months.
A 6 6 cm2 lump was observed in the right occipitoparietal region on CT (Figure 1). Ophthalmoscopy revealed bilateral disc swelling.
What was the diagnosis?
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Answer
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The unenhanced axial CT image shows a dense lesion in the right occipitoparietal region (Figure 1a
). The lesion exhibits minimal enhancement and mass effect with effacement of sulci and slight contralateral shift of the midline (Figure 1b). There is an associated scalp mass. Coronal T1 weighted MRI images (Figure 2) demonstrate a hypointense lesion with patchy enhancement following intravenous gadolinium.
The history is very suggestive of immunosuppression, notably acquired immune deficiency syndrome (AIDS). A test for human immunodeficiency virus (HIV) was positive.
Contrast enhanced CT scan of the liver (Figure 3) demonstrates a non-enhancing lesion of heterogeneous density occupying most of the left lobe and extending into the caudate and right lobes. Drainage of the liver lesion under CT guidance revealed blast cells. Bone marrow aspiration showed large blasts of lymphoid lineage with Burkitt's features.
In view of the diagnosis of systemic lymphoma, the cranial CT and MRI findings are most likely to represent secondary lymphoma.
The differential diagnosis includes subdural haematoma, en-plaque meningioma and metastases. The site of the lesion makes toxoplasmosis, which occurs in the brain parenchyma, very unlikely. Subdural haematoma does not enhance with gadolinium. Extension of the disease process into extracranial soft tissues by permeation through the skull vault is unlikely in subdural haematoma or meningioma [1]. This appearance is much more typical of lymphoma and of aggressive metastases such as sarcoma metastases. Although the skull lesion was not actually biopsied in our patient, secondary lymphoma is more likely.
The immune system is integral to the prevention of carcinogenesis [2]. Up to 20% of patients with AIDS eventually develop lymphomas [2]. These are characteristically high grade and B-cell in type [2]. In patients infected with HIV, central nervous system (CNS) involvement by lymphoma is common; 9.4% of brains in a recent 10-year autopsy series of AIDS patients were affected [2].
Although primary CNS lymphoma (PCNSL) is more common in AIDS [1–4], the meningeal and extracranial involvement in our patient is more typical of secondary lymphoma [1, 3, 4]. PCNSL tends to involve the basal ganglia, the corpus callosum, the parenchyma and periventricular regions of the cerebral cortex, and the parenchyma of the pons and cerebellum [1–4].
The classical CT appearances of lymphoma are of an isodense to hyperdense lesion with minimal contrast enhancement [1]. However, low density lesions have also been described [1, 3, 4]. MRI is much more sensitive than CT [1, 3, 4]. MRI appearances on T1 weighted sequences are of a lesion hypointense to isointense to brain with variable enhancement following intravenous gadolinium adminstration [1, 3]. Enhancement may be irregular or show a peripheral ring pattern [1, 3]. Signal characteristics are variable on T2 weighting and high on fluid attenuated inversion recovery [3]. The variable signal on T2 weighting may be related to the amount of surrounding oedema [1]; in a section through the centre of the lesion, it may appear hypointense, whereas the partial voluming effect of the oedema may contribute to a higher signal in more peripheral sections.
Received for publication September 7, 2001.
Revision received October 16, 2001.
Accepted for publication October 25, 2001.
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References
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- Zimmerman RA. Central nervous system lymphoma. Radiol Clin North Am 1990;28:697–721.[Medline]
- Ciacci JD, Tellez C, VonRoenn J, Levy RM. Lymphoma of the central nervous system in AIDS. Semin Neurol 1999;19:213–21.[Medline]
- Thurnher MM, Rieger A, Kliebl-Popov C, Settinek U, Henk C, Haberler C, et al. Primary central nervous system lymphoma in AIDS: a wider spectrum of CT and MRI findings. Neuroradiology 2001;43:29–35.[CrossRef][Medline]
- Singh S, Cherian RS, George B, Nair S, Srivastava A. Unusual extra-axial central nervous system involvement of non-Hodgkins lymphoma: magnetic Resonance Imaging. Australas Radiol 2000;44:112–4.[CrossRef][Medline]
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