Background: Ectopic thymomas often occur in the upper mediastinum; however, they rarely arise in the middle mediastinum, especially on the dorsal side of the innominate vein and superior vena cava in the peribronchial region. Case presentation: Six years prior, a 27-year-old female presented to our department and was diagnosed with locally advanced left breast cancer. First, we administered chemotherapy including an anti-human epidermal growth factor receptor 2 antibody. The size of the tumor was markedly reduced, and a radical operation involving mastectomy and axillary lymph node dissection was then performed. The patient underwent radiotherapy after the mastectomy, followed by trastuzumab therapy; she continued to receive endocrine therapy thereafter. She underwent computed tomography once a year after the surgery, and a nodule in the middle mediastinum on the dorsal side of the innominate vein and superior vena cava in the parabronchial region was detected at 4 years. We speculated that the nodule was a solitary mediastinal lymph node metastasis from her breast cancer; therefore, we performed thoracoscopic resection of the tumor. We diagnosed the tumor as a thymoma. Currently, the patient visits our hospital to receive continuous hormone therapy for her breast cancer, and the latest computed tomography scan demonstrated no metastases from or recurrence of her breast cancer or thymoma. Conclusions: We report a case of ectopic thymoma in the middle mediastinum. The tumor, which was detected during systemic therapy for locally advanced breast cancer, was located on the dorsal side of the innominate vein and superior vena cava in the parabronchial region and was indistinguishable from a lymph node metastasis from breast cancer.

Background: Monoclonal gammopathy of renal significance (MGRS) is characterized as renal impairment caused by monoclonal protein but does not fulfill the criteria for specific hematologic malignancies. Most MGRS cases involve IgG, IgA, or light chains, but IgM‐MGRS remains poorly understood.Case: We present a 74‐year‐old woman with IgM‐κ monoclonal proteinuria who initially declined further evaluation. Later, anemia was identified, and a systemic work‐up revealed monoclonal immunoglobulin deposition disease in the kidney and symptomatic Waldenström macroglobulinemia. Treatment with a Bruton's tyrosine kinase inhibitor, namely tirabrutinib, rapidly resolved both proteinuria and anemia.Conclusion: This case highlights the importance of early renal biopsy and prompt intervention in suspected IgM‐MGRS.

Background: Cold agglutinin-associated hemolysis (CAH) occurs in diverse clinical con-texts, including primary cold agglutinin disease (pCAD) and Waldenström macroglobu-linemia-associated cold agglutinin syndrome (WM-CAS). The differentiation of these enti-ties is often challenging, particularly in MYD88 L265P-negative cases. Since studies that examined the effects of chemoimmunotherapy (CIT) frequently predated routine molecular testing, it remains unclear whether the disease classification has an impact on treatment responses and durability. Methods: We retrospectively analyzed patients with pCAD, WM-CAS, and WM without CAS (WM-only) treated at a single center between April 2010 and November 2025. Diagnoses followed the revised fifth edition of the WHO Classifica-tion of Haematolymphoid Tumours. Clinicopathological features and outcomes were compared. Treatment responses were assessed using CAD-specific criteria based on he-moglobin and hemolysis markers. Time to next treatment (TTNT) and overall survival (OS) were analyzed using Kaplan-Meier methods. Results: Ten patients had CAH (5 pCAD, 5 WM-CAS) and 29 had WM-only. CAH cases showed higher lactate dehydrogenase and total bilirubin levels, whereas WM-only cases had higher serum IgM levels and greater bone marrow involvement. Rituximab-based CIT predominated as the first-line therapy for both pCAD and WM-CAS. Overall response rates were 100% in pCAD and 80% in WM-CAS, with similar kinetics. TTNT did not significantly differ between pCAD and WM-CAS. Elevated FDP was more frequent in CAH, while no overt thrombotic events or grade ≥3 infections were observed. Conclusions: Rituximab-based CIT effectively con-trolled CAH in both pCAD and WM-CAS, with similar durability. When hemolysis is the dominant clinical issue and the disease classification is unclear, tumor-directed therapy represents a treatment strategy.