ML-4 A case of primary CNS lymphoma diagnosed 5 years after stereotactic radiosurgery

Central nervous system primary malignant lymphoma (PCNSL) is rarely diagnosed as multiple metastatic brain tumors. Almost tumors recure early after receiving stereotactic radiosurgery (SRS). Regardless of the fact, the following case report displays PCNSL, diagnosed five years after the initial treatment with SRS as brain metastases of unknown primary origin. This extraordinal case suggests long-term follow-up regarding PCNCL. The case was a 55-year-old woman with a history of a total hysterectomy for cervical cancer. She developed left paralysis. Brain MRI confirmed a 27 mm contrast-enhanced lesion in the right frontal lobe and three other lesions. SRS was performed as a diagnosis of multiple brain metastases for urgent symptom relief. No extra-cranial cancerous lesions were found. Unknown primary cancer was a probable diagnosis at that time. Two years after SRS, local regrowth of tumor of the right frontal primary motor area was discovered. Re-irradiation was performed. Cerebral edema, contrast enhancement, and left paralysis progressed following five months, taking an oral corticosteroid. Craniotomy and debulk. The pathological diagnosis was brain radiation necrosis due to no viable tumor cells. New lesions in the left temporal lobe and basal ganglia appeared three years after surgery. Awake craniotomy was performed for the left temporal lobe lesion. Histopathology showed diffuse growth of tumor cells with a high nucleo-cytoplasmic ratio and irregular nuclear shape. Immunohistochemistry revealed positive CD10, CD20, CD45 (LCA), MUM1, and negative CD3, CD5. The Ki- 67 labeling rate was as high as almost 100% to diagnose diffuse large B-cell lymphoma, PCNSL. Multidrug chemotherapy consisting of rituximab, high-dose methotrexate, procarbazine, and vincristine were performed. Complete remission was obtained without any serious adverse events. Considering the residual radiation necrosis, whole-brain irradiation was avoided. Moreover, consolidation therapy was performed only with high-dose cytarabine therapy.