A 65-year-old man was urgently transported to a neurosurgical hospital on May 19, 2019 with a generalized seizure. A space-occupying lesion with midline deviation was found in the left frontal region of his brain (Fig. 1A), and a craniotomy tumor removal was performed on May 21. The tumor was distributed in layers in the subcranial subcutaneous tissue with a hematoma inside and outside the dura mater. Hematoxylin and eosin staining was was performed according to routine hospital procedures. The pathological diagnosis of the tumor was MALT lymphoma (Fig. 1B). Although flow cytometry was positive for CD20, CD19, cell surface kappa, and HLA-DR, and G-band pattern showed poor proliferation, fluorescence in situ hybridization (FISH) was negative for BIRC3-MALT1 translocation. Moreover, the patient was in the MALT Lymphoma Clinical Stage IVA IPI High-Intermediate risk group. Rituximab was used in combination for systemic therapy, and on July 17, 2019, treatment was started with rituximab 375 mg/m² (Day 1) and bendamustine 90 mg/m² (Days 2 and 3: R-Bendamustine). Methotrexate 12 mg and prednisolone 10 mg were only administered intrathecally the first time (because the cytodiagnosis was Class I). Six courses of the same regimen were administered thereafter. Symptoms such as headaches and seizures quickly improved with the first treatment, and by the time treatment was completed, his disability had also improved. The lesions shrunk (Fig. 1C) and are currently being monitored.

A 55-year-old man underwent a medical checkup in June 2010, and a computed tomography (CT) scan showed a parasternal tumor and axillary lymphadenopathy. In July of the same year, a sternum tumor and right axillary lymph node biopsy was performed, and marginal zone B-cell lymphoma was diagnosed. At the first visit, his immunoglobulin M (IgM) was 1,981 mg/dl (normal 400 mg/dl), and IgM-κ type M protein was detected by immunoelectrophoresis. Since Helicobacter pylori (H. pylori) was detected in his stomach in August 2010, H. pylori was eradicated with clarithromycin 400 mg, amoxicillin 1500 mg, and a proton pump inhibitor in anticipation of lymphoma reduction without any effect. Thus, on Day 1, rituximab 375 mg/m² was administered; on Day 2, cyclophosphamide 750 mg/m², doxorubicin 50 mg/m², and vincristine 1.4 mg/m² were administered; on Days 2-6, prednisolone 60 mg/day was administered. However, no symptoms such as fever or general fatigue were observed. IgM did not decrease at all and was determined to be unaffected. In September 2010, the symptoms improved from daily administration of thalidomide 100 mg and prednisolone 10 mg, but the sternum tumor did not shrink. In November, radiation therapy was performed at 40 Gy/20 Fr on the sternum tumor and bilateral axilla. The tumor shrunk, and the thalidomide was discontinued. In October 2014, a CT scan revealed a soft mass in the left heart diaphragm angle. In December 2014, a thoracoscopic longitudinal tumor resection was performed, and a recurrence of a marginal zone lymphoma was diagnosed. Flow cytometry was positive for CD20, CD19, cell surface kappa, and HLA-DR. G-band pattern showed no chromosomal abnormalities, and FISH was negative for BIRC3-MALT1 translocation. Since then, we have been following the patient after re-administration with prednisolone to maintain remission. In July 2016, interleukin-2 receptor (IL-2R) and IgM increased again, but the chest and abdominal CT scan showed no new lesions. However, an image with contrast enhancement showed thickening on the left parietal lobe in the head MRI performed in August 2016 (Fig. 1D). A dural biopsy was performed in September 2016. Hematoxylin and eosin staining was performed according to routine hospital procedures. Small- and medium-sized lymphocytes were diffused in the dura mater tissue (Fig. 1E), and it was determined that a marginal zone lymphoma had recurred. Since the patient did not desire a cerebrospinal fluid (CSF) injection, rituximab was used in combination for systemic therapy. Four courses of R-Bendamustine were administered, and the dural lesion disappeared (Fig. 1F). In February 2019, positron emission tomography was performed and detected multiple bone metastases. R-Bendamustine was used, but the patient stopped using it because he was allergic to it. After that, four courses of FCM therapy (Day 1: Mitoxantrone 8 mg/m²; Days 1-3: Fludarabine 25 mg/m² and Cyclophosphamide 200 mg/m²) were performed, and remission was achieved. The patient is currently undergoing follow-up, and the dural lesion has not recurred during the course.