Primary Vitreoretinal Lymphoma

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Chapter 156 Primary Vitreoretinal Lymphoma

Introduction

Primary vitreoretinal lymphoma is a rare intraocular malignancy with typical clinical features that help to distinguish it from other forms of ocular lymphoma. In order to review clinical and management aspects of vitreoretinal lymphoma, it is important first to clarify the terms primary central nervous system lymphoma (PCNSL) and primary intraocular lymphoma.

PCNSL is a variant of extranodal non-Hodgkin lymphoma (NHL) that is predominantly a high-grade B-cell malignancy associated with a median survival ranging from 1–8 years depending on factors such as age and Karnofsky performance status.1 It originates in the brain parenchyma, spinal cord, leptomeninges, and eyes.24 Formerly used descriptors such as “reticulum cell sarcoma” and “microgliomatosis” are no longer preferred as both misleadingly imply that the lymphoma arises from transformed reticulum or microglial cells.5,6

Primary intraocular lymphoma (PCNSL-O or PIOL) is a variant of PCNSL with predominantly ophthalmic involvement. In contrast to other ocular lymphomas that affect the orbit, conjunctiva, and uveal tract, PCNSL-O is characterized by vitreoretinal involvement and is therefore referred to as primary vitreoretinal lymphoma (PVRL). It is important to distinguish PVRL from other forms of primary intraocular lymphoma, particularly the primary uveal lymphomas. Primary choroidal lymphoma is generally a low-grade B-cell lymphoma that behaves similarly to extranodal marginal zone (EMZL) lymphomas found elsewhere in the body, while primary iridal lymphoma can be either of B-cell or T-cell origin.

Epidemiology

PCNSL accounts for 1–2% of all cases of lymphoma and approximately 3–5% of primary tumors of the central nervous system.79 From 1973–1997, the incidence of PCNSL increased threefold, partially owing to the corresponding rise in individuals with human immunodeficiency virus (HIV) infection and possibly due to improved diagnosis and/or detection leading to more cases being ascertained.7 Rates have since stabilized with an age-adjusted incidence of PCNSL in the USA of 4.8 per million population reported in 2002.7 PCNSL is therefore a rare disease affecting fewer than 2000 individuals annually in the USA.4

While PVRL is frequently seen in the setting of PCNSL, the exact incidence is unknown. Between 1999 and 2002, approximately 100 new cases of PVRL were reported in the USA.10 The association between PVRL and PCNSL is variable, with CNS disease manifesting prior to, following, or occurring simultaneously with ocular presentation. Approximately 25% of patients with PCNSL will have concomitant PVRL.3 In contrast, 56–85% of individuals with PVRL will ultimately develop central nervous system involvement.1114 Among immunocompetent individuals, the peak incidence of PVRL occurs between ages 50 and 70 years. In the immunocompromised population, PVRL occurs in younger individuals.1517 There are no known racial or ethnic associations. In a large, multicenter retrospective review of 221 patients with PCNSL with intraocular involvement, a slight female predominance (57%) was observed.18

Etiology and pathogenesis

PCNSL is believed to originate from late-germinal center or post-germinal center lymphoid cells, however the neurotropic mechanism by which these cells localize to the CNS remains uncertain.19 It has been hypothesized that the trafficking of lymphoma cells from the brain to the eye and vice versa involves either invasion of the optic nerve, seeding through shared venous drainage of the brain and eye, or common integrin expression of both organs.4 While there are no known risk factors for the development of PCNSL in immunocompetent individuals, immunosuppression secondary to HIV, congenital immunodeficiency, and iatrogenic immunosuppression are risk factors.20 PCNSL develops in as many as 6% of patients with acquired immune deficiency syndrome (AIDS).21,22 Epstein–Barr virus infection of B-lymphocytes in the absence of T-suppressor lymphocytes results in uncontrolled lymphocytic proliferation. Rare cases of PVRL may be secondary to human T-cell lymphotropic virus type 1 (HTLV-1) infection.23

Clinical findings

Ophthalmic findings

While individuals may be asymptomatic, more than half present with painless, decreased visual acuity or floaters.13,24,25 Of those who are asymptomatic, many are diagnosed when ophthalmic screening examination is performed for individuals with known PCNSL. The clinical findings are bilateral in 80% of cases, but are frequently asymmetric.11

The hallmark of PVRL is the presence of fine vitreous cells or clumps of cells and sub-retinal pigment epithelium (RPE) deposits comprised of aggregated lymphoma cells (Fig. 156.1).2628 When present, these lesions are considered pathognomonic.28 Anterior segment findings including keratic precipitates, iris nodules, aqueous cells, and flare are frequently encountered but are nonspecific.17,25 On fundus examination, focal, multifocal, or diffuse choroidal, retinal, or chorioretinal infiltrates can be seen in the presence or absence of vitreous cells (Fig. 156.2).26,29 Other less commonly reported findings include: perivasculitis (Fig. 156.3),13 retinal artery occlusion,30 exudative retinal detachment,31 multifocal “punched-out” lesions at the level of the RPE,32 and optic atrophy.33

Diagnosis

Diagnostic evaluation should begin with a thorough history that explores questions related not only to ocular symptoms, but also to changes in cognitive functioning, neurological deficits, and risk factors for immunocompromise. A detailed ophthalmic examination of both the anterior and posterior segment is required to assess the extent of disease and to establish laterality. In the setting of existing PCNSL, the diagnosis is straightforward and biopsy of an ophthalmic site is not necessary if the clinical findings are compatible with the diagnosis.

In the absence of prior CNS disease, the diagnosis of PVRL is based upon histopathological and cytological features. Several techniques exist for biopsy to establish the diagnosis including vitreous biopsy, retinal biopsy, and subretinal biopsy. Most commonly, diagnostic 23-gauge pars plana vitrectomy is performed. Proper surgical techniques and handling are critical as aspirates are generally of low cellularity and fragile lymphoma cells are prone to lysis during sample collection. Techniques vary by center and expertise; however, it is generally recommended that an undiluted vitreous sample of approximately 1–2 mL be collected prior to the start of the saline infusion during vitrectomy.20,36 Following collection of the first sample, the infusion fluid is started, and a second diluted vitreous specimen using gentle vitreous cutting can be collected in a separate syringe.37 Some centers also submit the vitreous cassette as a third sample.38 It is recommended that samples be delivered to the laboratory, without fixative, within one hour of surgery.36,39 Repeated vitreous biopsies are commonly performed in order to establish the diagnosis. In a study of 20 patients with PVRL, three eyes required more than one vitreous biopsy before the diagnosis was confirmed.40 More recently, there has been an interest in using 25-gauge sutureless vitrectomy for diagnostic purposes and for improved patient comfort and decreased operative times. This technique has been used with success in some centers.38

When chorioretinal or subretinal lesions are present, a retinal or subretinal biopsy may be performed. A subretinal biopsy technique using a standard three-port pars plana vitrectomy approach has been described.41 An initial core vitrectomy is performed allowing access to the subretinal infiltrate. Vitreous separation is then induced and thorough vitrectomy is performed over the biopsy site. An incision in the overlying retina just large enough to allow entrance of the vitreous cutter is then made. Suction tubing is then inserted through the retinectomy incision and with gentle cutting action, several samples are obtained. Subretinal aspirates should be placed in a mild cytofixative, such as herpes-glutamic acid buffer mediated organic solvent protection effect (HOPE) fixation or CytoLyt® (Cytyc Corporation).36

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