Occult tumors presenting with negative imaging: analysis of the literature

A review

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Some patients presenting with neurological symptoms and normal findings on imaging studies may harbor occult brain tumors that are undetectable on initial imaging. The purpose of this study was to analyze the cases of occult brain tumors reported in the literature and to determine their modes of presentation and time to diagnosis on imaging studies.


A review of the literature was performed using PubMed. The authors found 15 articles reporting on a total of 60 patients with occult tumors (including the authors' illustrative case).


Seizures were the mode of initial presentation in a majority (61.7%) of patients. The initial imaging was CT scanning in 55% and MRI in 45%. The mean time to diagnosis for occult brain tumors was 10.3 months (median 4 months). The time to diagnosis (mean 7.5 months, median 3.2 months) was shorter (p = 0.046) among patients with seizures. Glioblastoma multiforme (GBM) was found more frequently among patients with seizures (67.6% vs 34.8%, p = 0.013). The average time to diagnosis of GBM was shorter than the time to diagnosis of other tumors; the median time to diagnosis was 3.2 months for GBM and 6 months for other tumors (p = 0.04). There was no predilection for side or location of occult tumors. In adult patients, seizures may be predictive of left-sided tumors (p = 0.04).


Based on the results of this study, the authors found that in patients with occult brain tumors, the time to diagnosis is shorter among patients with seizures and also among those with GBM.

Abbreviation used in this paper:GBM = glioblastoma multiforme.

Article Information

Address correspondence to: Anil Nanda, M.D., Department of Neurosurgery, Louisiana State University Health Sciences Center, 1501 Kings Highway, Shreveport, Louisiana 71130-3932. email: ananda@lsuhsc.edu.

Please include this information when citing this paper: published online April 13, 2012; DOI: 10.3171/2012.3.JNS112098.

© AANS, except where prohibited by US copyright law.



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    Axial CT head scan obtained without contrast revealing a hyperdensity in the left frontal region. There were no abnormalities noted in the images.

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    Axial MRI studies of the brain with and without Gd contrast agent revealing the presence of a nonenhancing left frontal lesion. The lesion appeared hypointense on T1-weighted images obtained with Gd contrast (left), and it appeared hypointense on T2-weighted images as well (right). A diagnosis of unruptured cavernous malformation was made based on the typical MRI findings.

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    The patient presented next with altered mental status and headaches. At this time, a head CT scan performed without contrast agents in the emergency department revealed a hyperdense lesion (left) and a large amount of edema (right) in the left frontal region.

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    Axial MRI studies of the brain revealing a large border-enhancing lesion in the left frontal region (left), with evidence of severe edema in the left frontal region (right).

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    An MRI study of the brain obtained at the time of diagnosis revealed that the originally discovered left frontal cavernous malformation had been displaced posteriorly due to neoplastic expansion. Axial Gd-enhanced T1- (A) and T2-weighted (B) images reveal the cavernous malformation. A sagittal Gd-enhanced T1-weighted image (C) reveals the new location of the displaced incidental cavernous malformation.

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    Low-power photomicrograph demonstrating the presence of a markedly cellular glial neoplasm with microvascular proliferation and pseudopalisading necrosis. H & E, original magnification × 200.

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    High-power photomicrograph showing the astrocytic character of mildly to moderately pleomorphic neoplastic glial cells. Abundant typical and atypical mitotic figures are present. H & E, original magnification × 400.

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    A graphic representation of the growth rate of occult tumors. The x axis represents days, with initial clinical presentation at Day 0. The imaging characteristics (median duration) identified in this study are represented above the x axis. Below the x axis are the potential investigative and therapeutic intervention points along the timeline. Above the x axis, the potential change in size of these tumors is depicted. A deeper understanding of growth rates of occult tumors from large studies will assist in making these points clear and based on evidence.



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