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Brain tumour mimics and chameleons
  1. David Bradley,
  2. Jeremy Rees
  1. National Hospital for Neurology and Neurosurgery, London, UK
  1. Correspondence to Dr Jeremy Rees, The National Hospital for Neurology and Neurosurgery, Queen Square, Mailbox 99, London WC1N 3BG, UK; j.rees{at}ion.ucl.ac.uk

Abstract

The timely diagnosis of a brain tumour is crucial to optimising outcome in a group of patients with limited survival. Several common neurological conditions mimic brain tumours, causing concern to patient and physician until the correct diagnosis becomes clear. In addition, atypical presentations of brain tumours may cause diagnostic confusion, acting as chameleons and delaying correct workup and treatment. This review focuses on the important mimics and chameleons encountered in clinical practice, aiming to illustrate the wide range of clinical neurology encountered in this specialty and to provide guidance on reaching the correct diagnosis.

  • NEUROONCOLOGY
  • MRI

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Introduction

Primary brain tumours account for approximately 2% of adult cancers, with an incidence of around 10 to 20 per 100 000 per annum, and overall carry a 25% mortality rate.1 ,2 They are classified according to their histological phenotype into four grades, I—IV, and may be subdivided into low grade (I and II) and high grade (III and IV) tumours. These gradings correlate with prognosis and guide management—as a general rule, surgery or surveillance is recommended for low-grade gliomas, while surgery and a combination of chemotherapy and radiotherapy for high-grade gliomas. Different considerations apply in children.

The mode of presentation of brain tumours often indicates tumour grade. Low-grade tumours typically present several years into their natural history, with seizures, evolving personality change or minor neurological deficits. They may occasionally be found incidentally on imaging. In contrast, high-grade tumours present subacutely with rapidly evolving neurological deficits, symptoms of raised intracranial pressure, rapid cognitive decline or seizures. The ‘2-week wait’ criteria outline the common red flags suggested to general practitioners that should prompt referral to the cancer network (table 1).3 However, due to the non-specific nature of early brain tumour symptoms, the conversion rate from ‘suspected’ to ‘confirmed’ brain cancer was less than 1% in one 3-year prospective audit of 1,000 new referrals on the 2-week wait criteria in the UK.4 In our service, a recent study of 139 new patients with glioma showed that the common acute presentations were focal neurological signs (32%), seizures (23%), cognitive symptoms (8%), headache (6%), falls (5%), sensory disturbance (2%) and multiple symptoms (24%) (unpublished data). None of these is specific to brain tumours but warrant imaging, which leads to a diagnosis of tumour. In practice, tumour mimics (non-neoplastic disorders presenting with features suggestive of brain tumours) and chameleons (unusual presentations of brain tumours mistaken for other diagnoses) are common diagnostic problems requiring a high level of clinical awareness to avoid inappropriate workup and treatment. Assessment depends very much on context and can be divided into clinical and radiological mimics/chameleons.

Table 1

The ‘2-week wait’ criteria for brain tumour pathway referral

Brain tumour mimics: mistaking other diseases for brain tumours

Neurologists encounter a wide range of brain tumour mimics in clinical practice, including vascular, infective, inflammatory, toxic and metabolic lesions. Furthermore, in cases where there is cancer, they must decide its origin in order to manage the patient appropriately. Table 2 summarises some common mimics and helpful clues to their diagnosis.

Table 2

Disorders that can mimic brain tumours, along with diagnostic clues

Mimics: different tumour types

An important decision when faced with a scan consistent with a brain tumour is whether the patient has a primary tumour (glioma, lymphoma or meningioma being the main differential) or brain metastases. All cases of possible central nervous system (CNS) malignancy should be reviewed at a multidisciplinary team meeting before deciding on any definitive workup and intervention.

Metastases

While multiple lesions clearly favour metastatic disease, it can prove difficult to distinguish from multifocal glioma on radiological grounds alone. Multifocal gliomas account for about 5% of gliomas and occasionally one of the phacomatoses underlie multifocal tumours (neurofibromatosis types 1 and 2, von Hippel–Lindau syndrome, or tuberous sclerosis). In suspicious cases, it is essential to request body imaging (eg, computerised tomography (CT) chest/abdomen/pelvis +/− mammography/testicular ultrasound). Solitary mass lesions with more vasogenic oedema than would be expected should also be screened for cancer (figure 1). Clearly, it is better to obtain a histological diagnosis from a non-CNS site in cases of suspected brain metastases.

Figure 1

A 57-year-old woman presented with left leg weakness and headache. There was a heterogenous hyperintense lesion in the left parafalcine region with vasogenic oedema on T2-weighted MRI and fluid attenuated inversion recovery (A and B), that enhanced on postgadolinium T1 imaging (C and D). There were no systemic symptoms, initial chest X-ray was normal (E) and she was referred to the neuro-oncology multidisciplinary team for discussion. A primary lung cancer was shown on subsequent CT scan of the chest (F).

Lymphoma

Primary CNS lymphoma must be considered in patients with imaging compatible with malignancy. This may also present with multifocal lesions and spread intracranially at progression. In these patients, prior treatment with corticosteroids may lead to rapid tumour regression, leaving diagnostic uncertainty—as inflammatory lesions may also regress—and the absence of a biopsy target. For this reason, we would recommend withholding coritcosteroids if the scan suggests primary CNS lymphoma, unless there is evidence of raised intracranial pressure or severe neurological deficit (figure 2).

Figure 2

An 81-year-old man was admitted to the acute stroke unit with evolving left-sided weakness. His imaging was felt to represent high-grade glioma, with a rim-enhancing lesion, oedema and mass effect in the right centrum semiovale on plain CT scan of head (A) and subsequent postcontract CT the next day (B). He was started on dexamethasone 8 mg twice daily pending multidisciplinary team review and a decision on surgical management. A follow-up CT showed marked resolution at 3 weeks on precontract and postcontract CT (C and D), consistent with lymphoma. He deteriorated before a biopsy was obtained, and was treated with best supportive care.

Low-grade mimics of malignant brain tumours

Occasionally, high-grade tumours present with features of benign or low-grade lesions (eg, meningioma, cavernoma). High-grade transformation of a low-grade lesion is usually an imaging diagnosis and patients starting imaging surveillance for low-grade tumours should be reimaged if they present with rapidly evolving clinical signs, to avoid missing a high-grade diagnosis (figure 3).

Figure 3

A 46-year-old woman was evaluated for headache and seizures. Initial imaging was felt to be compatible with a left insular cavernoma on T2 and T2*-weighted images (A and B). However, follow-up imaging after 3 months showed a complex lesion with rapid growth and central haemorrhage and necrosis on T2-weighted and susceptibility-weighted sequences (C and D); there was avid heterogenous enhancement (E) and a new rim-enhancing lesion in the temporal pole. A diagnosis of glioblastoma multiforme was made on biopsy.

Mimics of high grade tumours

Infection

Numerous infective processes mimic high-grade brain tumours, and most (particularly tuberculosis) carry the inherent danger of exacerbation if the clinician assumes it is tumour and administers corticosteroids. Fever, risk factors (eg, known immunosuppression, recent travel, invasive procedures) and an acute time course may help, as may laboratory measures (serum C-reactive protein, white cell count). However, abscesses, toxoplasmosis and tuberculomas may be indistinguishable from high-grade gliomas, and may feature rim enhancement, necrosis, haemorrhage and perilesional oedema with mass effect. Lumbar puncture may be unsafe due to supratentorial mass effect (figure 4). Herpes simplex viral encephalitis may be associated with haemorrhage, raising the possibility of a high-grade tumour on imaging. Radiologically, the presence of highly restricted diffusion within the lesion suggests abscess more than tumour.

Figure 4

A 49-year-old man, originally from Ethiopia and resident in the UK for 15 years, presented with acute headache and a seizure. On examination, he had a dense left homonymous hemianopia. His history included cerebral venous sinus thrombosis 2 years previously. Imaging showed a multilobulated mass in the right occipital lobe associated with significant oedema and mass effect on fluid attenuated inversion recovery and T2 MRI (A and B); the lesions were rim enhancing on T1 postgadolinium sequences (C and D). There were dilated cortical veins secondary to prior venous sinus thrombosis. A biopsy showed a lymphocytic and plasma cell chronic inflammatory infiltrate with prominent macrophages and granulomas. He was treated empirically with standard antituberculous therapy and maintained on long-term antiepileptic medication. Ten years later, he remained seizure-free with a residual hemianopia.

Tumefactive multiple sclerosis

This condition may be associated with evolving neurological deficits or personality change and is characterised by T2-hyperintense MRI lesions greater than 2 cm diameter, with surrounding oedema, enhancement and mass effect, that may mimic high-grade tumour. A reactive cerebrospinal fluid (CSF) with oligoclonal bands may help, although tumefactive lesions as the presenting episode of multiple sclerosis are associated with a reduced likelihood of positive bands, in the region of 50%.5 Other clues include evidence of prior optic neuritis, other white matter lesions in the appropriate distribution (ie, bilateral periventricular, or in the corpus callosum). It should be noted, however, that gliomas commonly infiltrate the corpus callosum and this should be differentiated from the punctate lesions typical of demyelination in that region. Further helpful MRI features include hypodensity on plain CT scanning in regions that enhance on MRI6 and, when present, an ‘open-ring’ pattern of enhancement within the defect at the grey-white interface7 (although most tumefactive lesions are full-ring enhancing6) (figures 5 and 6).

Figure 5

A 17-year-old girl presented to the eye casualty with headache and double vision. On examination, there was a right sixth nerve palsy and a left homonymous quadrantanopia. MRI showed a solitary large enhancing mass lesion on T1 postcontrast (MR image) in the right parieto-occipital lobe, thought to represent a high-grade primary tumour. There were no other lesions. Biopsy showed a sharply demarcated lesion to the right on H&E staining (A) with significant macrophage infiltration (B) and loss of myelin (C) with relative preservation of axons (D). A diagnosis of demyelination was made.

Figure 6

A 53-year-old man with a background of a germ cell tumour presented with rapid loss of vision in his right eye. Imaging showed a large cystic lesion in the left frontal region on T2 (A) and a further smaller hyperintense lesion in the right parafalcine region on T2 (B). There was no enhancement. Body imaging showed new retroperitoneal disease on positron-emission tomography. He was referred for management of brain metastases and received chemoradiotherapy for his systemic disease. One year before, he had experienced an episode of unsteadiness and double vision, responsive to corticosteroids; this history prompted a diagnosis of tumefactive multiple sclerosis, consistent with the rim of restricted diffusion seen on diffusion-weighted and apparent diffusion coefficient imaging (C and D). Further T2 imaging following corticosteroid treatment showed significant regression after several weeks (E and F).

Mimics of low-grade tumours

Stroke

Sudden onset of focal negative neurological deficits usually represents stroke in clinical practice. While the symptom time course should easily differentiate this from tumour, patients may present to stroke units because they have had a seizure and are found to have persisting lateralised signs. In the acute setting, this may raise the possibility of seizure at stroke onset if the patient has been unaware of symptoms evolving or is in a postictal state and cannot provide history. Patients may have truly hyperacute neurological signs due to tumour-associated haemorrhage. Hypodensity outside of a vascular territory aids the differentiation between tumour and stroke, as may the pattern of enhancement on postcontrast CT scan.

Infection

Viral encephalitis may present with confluent hyperintensity in the frontotemporal region on MRI, associated with cognitive symptoms, headache and confusion. The time course usually helps, along with raised inflammatory markers and positive PCR on CSF analysis. Empirical antiviral treatment should be given where viral encephalitis is suspected. Hyperintensity on MRI following resolution of herpes simplex viral encephalitis may persist but does not expand, and mass effect, perfusion abnormalities or enhancement should generally have resolved 6–10 weeks after successfully treated disease. Therefore, a MR brain scan at 3 months will usually identify other pathology, if not clinically apparent before this.

Inflammation

Occasionally, an atypical or unilateral distribution of multiple sclerosis lesions, or rarely other inflammatory disorders, may mimic a low-grade brain tumour. Steroid-responsiveness is typical but may also be associated with lymphoma and it is important to be cautious in reaching an inflammatory diagnosis. MR spectroscopy may allow differentiation of inflammatory lesions from neoplasia (a typical inflammatory spectroscopy pattern being elevated choline/creatine ratio with a normal N-acetylaspartate/creatine ratio and elevated lactate). Some cases may require a biopsy. Rarely, true demyelinating lesions (‘sentinel lesions’) may herald the onset of primary CNS lymphoma.8

Autoimmune encephalitis

Patients with a variety of antibody-mediated encephalitides may present with seizures, psychiatric symptoms and cognitive/personality change and may have asymmetric (even unilateral) medial temporal or more widespread MRI change, consistent with low-grade glioma. In these cases, CSF pleocytosis often helps while awaiting serology. The aggressive acute progression of these conditions typically leads to the correct clinical diagnosis but there is occasionally uncertainty. It is important to note that this condition may be paraneoplastic depending on the antibody found (the most commonly associated being antibodies to Hu, CRMP5, Ma2 and amphiphysin) and patients should undergo the appropriate workup for an underlying tumour.9 ,10

Longstanding/congenital lesions

Longstanding or congenital lesions may be confused with low-grade glioma. Examples include cortical dysplasia, cortical migration defects, complex cysts and sequelae of congenital or early infection, for example, malaria, cycticercosis or sequelae of ‘TORCH’ infections (toxoplasmosis, rubella, cytomegalovirus and herpes simplex). Calcification is common in congenital/childhood infection but also occurs in some tumour subtypes, for example, oligodendrogliomas. Rarely, the MRI appearances of other benign lesions, for example giant Virchow–Robin spaces, may raise the possibility of CNS malignancy, especially if associated with adjacent white matter change.11 While such benign lesions are readily identified as incidental if there is no history suggesting evolving malignancy, it may be less straightforward if patients have undergone imaging for symptoms of headache or cognitive decline. Aneurysm should be included in the differential of parasellar lesions in particular, and occasionally dural arteriovenous fistulas may mimic a tumour—these lesions are easily seen on dedicated vascular imaging.

Mimics of recurrence in patients with treated brain tumour

Radionecrosis/pseudoprogression

Differentiating tumour progression from radionecrosis is critical to managing patients with treated malignant brain tumours. Radiotherapy can result in oedema, mass effect and breakdown of the blood–brain barrier that can be difficult to distinguish from tumour progression (figure 7). The underlying pathology is vascular fibrosis/thrombosis with inflammation. These effects are commonly seen years after initial treatment. ‘Pseudoprogression’, which is more frequent, is an earlier (first 3 months) phenomenon seen after chemoradiation of glioblastoma multiforme, comprising new enhancing lesions that are generally asymptomatic and regress spontaneously, but may be mistaken for early progression.12 Several imaging-based criteria using structural, functional and metabolic imaging have proven to be generally unreliable. More recently proposed methods that may provide greater sensitivity and specificity include the use of indices from dynamic contrast-enhanced MRI13 and the use of layering pattern on the apparent diffusion coefficient map.14 Given the frequency of ‘pseudoprogression’, many oncology units no longer perform early post-treatment MRI studies in order to avoid unnecessary anxiety and inappropriate interruption of important adjuvant chemotherapy.

Figure 7

A 50-year-old man with a biopsy-proven astrocytoma, treated with radiotherapy, presented with headache and confusion 6 months after completing treatment. His imaging showed a right hemisphere lesion with marked oedema on T2 and fluid attenuated inversion recovery (A and B) with avid ring enhancement (C and D). He underwent urgent debulking, and histology showed radionecrosis with no evidence of high-grade tumour.

Stroke

Patients with brain tumours may develop stroke for a variety of reasons many years after treatment, including radiotherapy-induced vasculopathy. Sudden onset non-evolving neurological deficit should allow differentiation from a tumour, but outside of the acute phase, worsened neurological function along with new T2-hyperintensity on imaging may be interpreted as tumour progression. Even in the acute phase, restricted diffusion associated with enhancement may mimic tumour extension (figure 8).

Figure 8

A 54-year-old woman presented with acute left-sided weakness and facial numbness. She had a background of grade II astrocytoma treated with surgery and radiotherapy 16 years before and breast cancer operated upon 2 years before. Biopsy was undertaken to assess for probable malignant transformation, seen as hyperintensity on T2 and fluid attenuated inversion recovery (A and B) that enhanced post gadolinium on T1 sequences (C and D) in the right striatum. Histopathology was consistent with infarction associated with radionecrosis, in keeping with the diffusion-weighted imaging (E and F).

Chameleons: unusual/atypical presentations of CNS malignancy

Tumour chameleons imitate other diseases, when they have a tempo of onset or symptoms that do not immediately suggest a tumour.

Infection

Occasionally, brain metastases and even high-grade tumours can present with clinical features and imaging characteristics compatible with an infective process (figures 9 and 10). The differential diagnosis of multiple ring-enhancing lesions includes pyogenic abscesses or tuberculosis. Another scenario is of an encephalitic presentation with headache, confusion and low-grade fever associated with unilateral temporal lobe hyperintensity on T2-weighted MRI. The symptom time course usually helps and patients should receive acyclovir cover in equivocal cases. Lack of resolution months after clinical recovery should prompt a tissue biopsy.15

Figure 9

A 79-year-old man presented with subacute confusion and word-finding difficulty on a background of mild headache. Cerebrospinal fluid (CSF) examination showed two white cells and negative PCR. Imaging showed unilateral temporal lobe hyperintensity on T2 and fluid attenuated inversion recovery (FLAIR) (A and B respectively) and he was treated empirically with intravenous acyclovir for presumed CSF-negative herpes simplex viral encephalitis with an appropriate clinical presentation. There was partial resolution of dysphasia during admission. Follow-up imaging at 12 months (C and D) showed progression, leading to a diagnosis of low-grade glioma. Three months later, his imaging was consistent with malignant transformation, with rapid superior expansion on T2 and FLAIR (E and F) that now enhanced (G).

Figure 10

A 30-year-old man presented with a generalised seizure along with acute onset low-grade fever, chills, headache, left-sided weakness and visual disturbance. His imaging showed extensive T2-hyperintensity in the left frontal, parietal and occipital regions (A and B) with areas of enhancement (C and D) felt to be suspicious for infection or an inflammatory process. Blood and cerebrospinal fluid workup was normal. Subsequent biopsy revealed anaplastic oligodendroglioma.

Normal or non-specific scan

Occasionally, patients present with focal seizures and the initial MRI shows only a non-specific abnormality. In these cases, where there is a high index of clinical suspicion, patients should be rescanned within 6 weeks (figure 11).

Figure 11

A 50-year-old man presented with partial-onset seizures. His imaging showed cortical and subcortical hyperintensity on T2 and fluid attenuated inversion recovery (FLAIR) at the left parietotemporal junction (A and B) with further abnormality towards the temporal pole on the left (C). The findings were felt to be compatible with cortical dysplasia. Seizures proved difficult to control and the patient developed right-sided sensory and motor symptoms along with headache. Further imaging showed evolution of a large heterogenous mass with vasogenic oedema on T2 and FLAIR (D and E) that had rim enhancement on the T1 post gadolinium sequence (F). A diagnosis of glioblastoma multiforme was made.

Stroke

CNS malignancy may be mistaken for stroke in cases where there are unilateral neurological deficits, particularly in cases presenting acutely and undergoing rapid assessment for possible thrombolytic therapy (figure 12). The typical CT findings in evolving stroke (eg, oedema, sulcal effacement or hypodensity) may also occur with low-grade gliomas. Gliomatosis cerebri (infiltrative low-grade glial tumour affecting three or more lobes) may also present through an acute stroke pathway with unilateral neurological deficits and CT imaging findings compatible with stroke (including the ‘dot’ sign).16

Figure 12

A 50-year-old man presented to the stroke unit with sudden onset of right leg heaviness and numbness. The symptoms improved by 90% over the next 12 h, and stroke workup was started. His CT stroke protocol was reviewed and showed subtle hyperdensity in the left parafalcine region (A) with a blush of contract on the CT angiogram in the same region (B) that is easier to see when rewindowed (C). A MRI showed hyperintensity and swelling on T2-weighted images (D) with avid ring enhancement on T1 postgadolinium sequences (E). There was a further area of hyperintensity in the right thalamic region on fluid attenuated inversion recovery (F) that did not enhance. Biopsy of the enhancing lesion confirmed high-grade glioma.

Optic neuritis

Patients presenting with symptoms compatible with optic neuritis occasionally have an infiltrative glioma of the chiasm or anterior visual pathways (figure 13). MRI will show a swollen chiasm or optic nerve. In addition, these patients either fail to improve or progress through corticosteroid therapy.

Figure 13

A 45-year-old man presented with rapidly progressive visual loss. MRI demonstrated multifocal hyperintensity of the optic chiasm on T2 and fluid attenuated inversion recovery (FLAIR) (A and B) that enhanced post gadolinium (C and D), along with a lesion in the left pontomedullary region on FLAIR (E and F), which also enhanced (G and H). A diagnosis of optic neuritis was made based on clinical presentation and a cerebrospinal fluid examination showing 65 leukocytes, and a trial of intravenous methylprednislolone was given. The lesions progressed through serial imaging and a diagnosis of high-grade glioma was made following biopsy.

Meningeal carcinomatosis

Patients with spread from primary cancer elsewhere may present with cranial neuropathies and symptoms of meningeal irritation where the meninges are involved. In patients known to have cancer the possibility of meningeal carcinomatosis should be aggressively pursued with gadolinium-enhanced MRI and high-volume CSF studies (three samples of at least 10 mL each)—compatible findings include raised protein, low glucose, pleocytosis and tumour cells on cytology (figure 14). Lymphocytes should be subtyped. A differential here includes paraneoplastic meningoencephalitis (eg, anti-Hu).

Figure 14

A 68-year-old woman with a background of breast cancer presented with acute loss of vision in the right eye. She was noted to have a swollen optic disc and a diagnosis of ischaemic optic neuropathy was initially made. Subsequent MRI showed periventricular high signal lesions on T2-weighted (A) and fluid attenuated inversion recovery (B) sequences, compatible with vascular disease or demyelination. Vascular workup was completed and was unremarkable. Cerebrospinal fluid (CSF) was normal. She then developed increasing unsteadiness and headaches. CT chest, abdomen and pelvis showed evidence of metastatic spread from her breast carcinoma. Repeat imaging showed evidence of leptomeningeal carcinomatosis on T1 post-GAD imaging with a right-sided prechiasmatic lesion (C) and infiltration of the right optic nerve with enhancement relative to the left (D). Repeat CSF showed malignant cells.

Haemorrhage

Intracerebral haemorrhage accounts for approximately 10% of stroke, increasing significantly after the age of 55 years; the question of primary versus secondary bleed must always be addressed. In some cases, location (eg, basal ganglia or thalamus) coupled with a history of hypertension, may strongly support the diagnosis of a primary hypertensive bleed. In an older patient with a lobar haemorrhage and multiple old microbleeds on susceptibility-weighted imaging or gradient-echo sequences, it is reasonable to suspect amyloid angiopathy. Underlying tumour may account for up to 11% of intracerebral haemorrhage;17–21 common lesions are glioblastoma multiforme or metastases from melanoma, colon, renal, lung or breast carcinoma. Intratumoural bleeds may lead to disproportionate mass effect and oedema, as well as enhancing satellite lesions. Many patients require interval imaging to identify secondary causes, including vascular lesions (eg, cavernoma, arteriovenous malformation) and CNS malignancy. It is important to note that patients with cancer show a generally increased prevalence of intracranial haemorrhage.22

Inflammatory conditions

CNS malignancy, particularly primary CNS lymphoma, can present with the clinical and imaging characteristics of inflammatory/autoimmune conditions. Subacute evolution of fluctuating cognitive/psychiatric symptoms, focal neurological deficits and seizures in a young patient may all suggest autoimmune encephalitis or, depending on imaging characteristics, fulminant demyelination or a multitude of inflammatory conditions, including sarcoidosis and systemic lupus erythematosus. Some of these conditions are associated with lymphadenopathy, raising the possibility of systemic malignancy. Useful red flags include a lack of systemic inflammatory features (eg, arthralgia, fever, rash), lack of specific imaging findings (eg, basal meningitis in sarcoidosis) and lack of inflammatory CSF findings. Where autoimmune encephalitis is confirmed on serology, it is important to pursue underlying malignancy in most cases. While it is more common for tumefactive multiple sclerosis to mimic a high-grade tumour, occasionally the reverse may be true where a patient felt to represent acute multiple sclerosis with enhancing lesions turns out to have lymphoma or metastases. Low-grade lesions may certainly be mistaken for inflammatory diagnoses, including multiple sclerosis, but serial imaging in tandem with clinical progression usually leads to the diagnosis (figures 10 and 15). In the case of lymphoma, there may be asymptomatic demyelinating lesions with enhancement on MRI at the onset of disease (‘sentinel lesions’). In one series of four patients, CSF was normal, biopsy showed demyelination with axonal sparing or non-specific inflammation, and the diagnosis of symptomatic B cell primary CNS lymphoma was detected only after 7–11 months.8 One hypothesis is control of evolving lymphoma by host immunity. We recommend that a patient aged over 50 years presenting with new enhancing lesions that show demyelination on biopsy should be closely monitored for evidence of primary CNS lymphoma.

Figure 15

A 39-year-old man presented with stuttering onset of facial numbness that initially improved, followed by rapidly progressive diplopia and ataxia. A provisional diagnosis of demyelination was made based on T2 hyperintensity in the posterior fossa and periventricular region on fluid attenuated inversion recovery (FLAIR) (A to C). Oligoclonal bands were negative and follow-up imaging at 2 months revealed dramatic progression throughout the brain on FLAIR (D to F) with avid enhancement on T1 postgadolinium sequences (G). A diagnosis of B cell primary CNS lymphoma was made, which was rapidly fatal.

Conclusion

The diagnosis of CNS malignancy can prove challenging, with several common mimics and important chameleons. All cases of suspected brain tumour should be discussed at a multidisciplinary meeting before planning formal investigation and management. Corticosteroids should be avoided in cases where there is no evidence of raised intracranial pressure or of severe/evolving neurological deficit. Empirical antimicrobial cover for infectious disorders should be started if there is uncertainty. Clinical and radiological findings should usually differentiate between CNS malignancy and its mimics, but biopsy is sometimes required to ensure the correct diagnosis and management.

References

Footnotes

  • Contributors DB wrote the manuscript and reviewed cases. JR reviewed cases and edited the manuscript.

  • Competing interests None.

  • Provenance and peer review Commissioned; externally peer reviewed. This paper was reviewed by Brenan McLean, Truro, UK.

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