Primary central nervous system lymphoma in an human immunodeficiency virus-infected patient mimicking bilateral eye sign in brain seen in fluorine-18 fluorodeoxyglucose-positron emission tomography/computed tomography.

Fluorodeoxyglucose-positron emission tomography/computed tomography (FDG PET/CT) has proven useful in the diagnosis, staging, and detection of metastasis and posttreatment monitoring of several malignancies in human immunodeficiency virus (HIV)-infected patients. It also has the ability to make the important distinction between malignancy and infection in the evaluation of central nervous system (CNS) lesions, leading to the initiation of the appropriate treatment and precluding the need for invasive biopsy. We report an interesting case of HIV positive 35-year-old woman presented with headache, disorientation, and decreased level of consciousness. She underwent whole body PET/CT which showed multiple lesions in the cerebrum which mimics bilateral eye in brain. A diagnosis of a primary CNS lymphoma was made and patient was started on chemotherapy.

INTRODUCTION

Three cancers are especially prevalent in human immunodeficiency virus (HIV)-positive individuals and are considered acquired immunodeficiency syndrome (AIDS) defining illnesses: Kaposi sarcoma, high-grade B-cell non-Hodgkin lymphoma, and invasive cervical carcinoma.[1] Several studies have evaluated the role of fluorodeoxyglucose positron emission tomography (FDG PET) in the diagnosis of central nervous system (CNS) complications in patients with AIDS, with particular attention paid to the differentiation between toxoplasmosis and lymphoma.[23] There are previous reports of F-18 FDG PET/computed tomography (CT) in HIV patients with cerebral lymphoma but the interesting mimicking bilateral eye sign in brain was not reported.

CASE REPORT

A 35-year-old female HIV patient presented with headache and altered mental status. She was referred for whole body PET/CT for detection of involvement of CNS and other sites. PET/CT showed an intense uptake in the multiple lesions noted in both the cerebrum [Figure 1], with a standardized uptake value (SUV max) of 30-35. A diagnosis of primary CNS lymphoma was made and she was started on chemotherapy.

Figure 1

Whole body fluorodeoxyglucose-positron emission tomography (PET)/ computed tomography (CT) Axial CT (a), PET (b), Fused PET/CT (c), maximum intensity projection image (d) showing intense uptake in the multiple lesions in cerebrum with an standardized uptake value max of 30-35

DISCUSSION

Neurologic complications occur frequently in HIV-positive patients because of opportunistic infection, malignancy, or the HIV itself.[3] As many as 10% of all AIDS patients will initially present with neurologic symptoms and between 40% and 60% of patients with AIDS will eventually develop CNS complications during the course of their disease.[4] The evaluation and management of HIV-positive patients presenting with neurologic findings is challenging because the symptoms at initial presentation, such as fever, headache, altered mental status, and focal neurologic signs or seizures, are not specific. In addition, conventional imaging techniques, such as CT or magnetic resonance imaging (MRI), are often not useful in determining the causes of mass lesions. For example, both primary CNS lymphoma and toxoplasmosis produce similar focal or multifocal ring-enhancing lesions on CT and MRI.[5]

Several studies have evaluated the role of FDG PET in the diagnosis of CNS complications in patients with AIDS, with particular attention paid to the differentiation between toxoplasmosis and lymphoma.[6] Hoffman et al.,[7] performed both a visual and semiquantitative evaluation of CNS lesions using FDG PET. In every case of lymphoma, FDG uptake was significantly higher than that of nonmalignant lesions. In a similar study, Villringer et al.,[8] assessed the ability of FDG PET to differentiate between toxoplasmosis and lymphoma. Eleven AIDS patients with CNS lesions were examined and the SUVs of the lesions were compared with that of a contralateral brain area to control for differential FDG uptake between lesions in white matter and those in gray matter. O'Doherty et al.,[9] measured SUVs ranging between 0.14 and 3.7 over cerebral lesions due to toxoplasmosis, significantly lower than the SUVs in lymphomas which had values between 3.9 and 8.7. FDG PET thus has promise as a reliable, noninvasive method of differentiating between primary CNS lymphoma infections. A low SUV of the lesion adds confidence to a working diagnosis of toxoplasmosis when treated empirically and may avoid a brain biopsy. However, definitive diagnosis can only be made by tissue diagnosis. Our case describes a classical finding in CNS lymphoma which mimics a bilateral eye sign in brain which has SUV max of 30-35.