Primary Vitreoretinal Lymphoma Workup

Overview

Primary vitreoretinal lymphoma (PVRL), a variant of primary CNS lymphoma, classically presents as chronic, steroid-resistant vitritis in elderly patients and is the prototypical malignant masquerade syndrome. In a patient in their late 60s or older with vitritis and no infectious cause found on standard workup — especially if the inflammation only partially responds to corticosteroids before recurring — PVRL should move to the top of the differential rather than being treated as one more round of idiopathic uveitis.

PVRL sits within the broader masquerade syndrome differential covered on the Masquerade Syndromes page, but because its workup is distinctive and time-sensitive — a delayed diagnosis has direct CNS implications — it gets its own dedicated page here.

Fundus and Histologic Findings

On fundus exam, PVRL infiltrating the subretinal space produces multifocal, creamy yellow-white subretinal infiltrates beneath the retinal pigment epithelium in a mottled "leopard-spot" pattern — a distinctive appearance that, combined with vitreous cells, should raise suspicion even before biopsy confirmation.

The vast majority of primary vitreoretinal (intraocular) lymphomas are diffuse large B-cell lymphoma (DLBCL) of the non-Hodgkin type, closely linked biologically to primary CNS lymphoma — which is why the two are worked up together (see below).

Diagnostic Workup

Because lymphoma cells are fragile and degrade quickly once removed from the eye, initial vitreous samples are often nondiagnostic. When cytology is inconclusive on the first attempt, a repeat diagnostic pars plana vitrectomy with prompt cytopathology processing is frequently needed to establish the diagnosis — this is the definitive diagnostic procedure for confirming suspected PVRL. Vitreous biopsy with cytologic and flow cytometry analysis remains the most useful confirmatory test overall, since it directly identifies malignant lymphocytes within the specimen and distinguishes lymphoma from an infectious or inflammatory process.

Two adjunctive tests support the diagnosis when cytology alone is equivocal:

• Vitreous interleukin ratio — IL-10 is elevated in B-cell lymphoma while IL-6 predominates in inflammatory conditions, so a vitreous IL-10:IL-6 ratio greater than 1.0 supports a diagnosis of intraocular lymphoma over uveitis.
• Molecular genetics — the MYD88 L265P mutation is found in a high proportion of primary vitreoretinal and CNS lymphomas and can be detected in vitreous samples to support diagnosis when cytology is equivocal.

Systemic and CNS Workup

Because PVRL is closely linked to primary CNS lymphoma, a patient newly diagnosed with PVRL should undergo contrast-enhanced MRI of the brain, often paired with a lumbar puncture for CSF cytology, to assess for concurrent CNS disease. This isn't an optional add-on — a meaningful proportion of patients with PVRL either already have or will go on to develop CNS lymphoma, so neurologic imaging is considered essential once the ocular diagnosis is made, not a follow-up step to consider later.

Clonality: Malignant vs. Reactive

Not every uveal lymphoid infiltrate is lymphoma — benign reactive lymphoid hyperplasia of the uvea can look similar clinically. The key histopathologic distinguishing feature is clonality: demonstration of monoclonality by immunohistochemistry (light-chain restriction) or molecular clonality studies indicates a malignant lymphoid process, whereas benign reactive hyperplasia shows a polyclonal population of lymphocytes. This distinction matters because it separates a watch-and-wait benign process from one requiring oncologic treatment and CNS surveillance.

High-Yield Pearls

If a first vitrectomy comes back nondiagnostic in a patient whose clinical picture still fits PVRL, don't let a negative cytology close the door — repeating the vitrectomy with prompt processing is standard, precisely because the malignant cells are so fragile in the first sample.

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