Non-Hodgkin lymphomas are malignant neoplasms of lymphoid tissue, and a subset present with extranodal involvement. The head and neck region represents one of the clinically relevant localizations. Sinonasal B-cell lymphomas are a rare subtype, most often manifesting as diffuse large B-cell lymphoma (DLBCL), and typically show aggressive clinical behavior. Relapses most frequently involve cervical lymph nodes, the orbit, and the central nervous system.

Ocular involvement is rare, usually presenting as orbital masses or ocular adnexal lymphoma. Vitreoretinal infiltration is even more unusual and has been described only infrequently.

In this case report, we present an elderly male patient with nasal cavity B-cell lymphoma who developed relapse with vitreoretinal involvement, aiming to emphasize the diagnostic and therapeutic aspects of this rare condition.

A 71-year-old male was diagnosed three years earlier with nasal cavity B-cell lymphoma. Bone marrow biopsy at diagnosis showed no systemic involvement. He received four cycles of R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone) and achieved complete remission.

Three years later, he presented with decreased vision in the left eye. Orbital MRI showed tortuosity of the optic nerve and slight widening of the perioptic space (Figure 1). Cranial MRI revealed only age-related changes. Cytology and flow cytometry of vitreous fluid demonstrated CD20 and CD79a positivity with high proliferative activity, consistent with B-cell neoplasia.

PET-CT revealed limited FDG uptake (SUVmax 5.02) in the anterior aspect of the left orbit (Figure 2), with no additional systemic involvement. Based on his disease history, systemic high-dose methotrexate combined with cytarabine and intrathecal therapy was initiated. Radiotherapy was also considered.

He was referred to another specialized center for possible intravitreal chemotherapy. Despite systemic treatment, follow-up revealed that the patient had died.

Sinonasal B-cell lymphomas are uncommon, most often exhibiting DLBCL histology with aggressive clinical features. Relapses most frequently involve cervical nodes, orbital structures, or the central nervous system. Although orbital disease is recognized, vitreoretinal infiltration is exceedingly rare and has been reported in less than 5% of cases in large series.

Diagnosis is challenging, as ocular involvement may present with non-specific symptoms such as visual impairment or vitreous opacities, requiring cytology, immunophenotyping, and immunohistochemistry of vitreous samples for confirmation.

Therapeutic options include systemic high-dose methotrexate and cytarabine, with intrathecal therapy commonly added for central nervous system prophylaxis. Radiotherapy may contribute to local control in orbital disease. Intravitreal chemotherapy has also been described, most often with methotrexate, and rituximab has been used in selected cases.

The prognosis of ocular involvement is poor, with median survival reported between 12 and 36 months and a high risk of central nervous system relapse. This case illustrates that vitreous infiltration may represent a relapse manifestation of sinonasal B-cell lymphoma and highlights the importance of careful evaluation of ocular symptoms in such patients.