Primary natural killer cell lymphoma of the lacrimal sac

Primary lymphoid tumors of the lacrimal sac are quite rare, and all reported cases are of B-cell tumors with good prognosis. To our knowledge, this is the first case of primary natural killer (NK) cell lymphoma of the lacrimal sac. A 55-year-old woman presented with a lacrimal sac tumor, and histological diagnosis of NK cell lymphoma was made. Although disease was initially localized to the right lacrimal sac, it invaded into the adjacent ethmoidal sinus before chemotherapy was initiated (clinical stage IIE). Epstein-Barr virus (EBV)-encoded small RNA (EBER) was detected in lymphoma cells by in situ hybridization. Systemic chemotherapy combined with intrathecal chemotherapy followed by local radiotherapy was performed, and the patient achieved complete remission. However, shortly after completion of chemoradiotherapy, the lymphoma relapsed with rapid systemic dissemination. The disease was refractory to chemotherapy, and the patient eventually succumbed due to sepsis.