Plasma cell-type Castleman disease (PCD) is a rare idiopathic atypical lymphoproliferative disorder. It is difficult to differentiate between PCD and IgG4-related disease (IgG4-RD) based on histology alone. As PCD often presents with abundant hemosiderin deposition, lymph node lesions obtained from 22 PCD patients and 12 IgG4-RD patients were analyzed using Prussian blue staining to clarify whether hemosiderin deposition is effective in distinguishing between these two diseases. The analysis disclosed that hemosiderin was more densely deposited in PCD than in IgG4-RD. The median number of Prussian blue-positive cells ± standard deviation (SD) in PCD and IgG4-RD cases was 13 ± 36 cells/3HPFs and 4 ± 8 cells/3HPFs (P = 0.034), respectively. In addition, we analyzed the relationship between hemosiderin deposition and levels of serum interleukin (IL)-6, serum C-reactive protein (CRP), and anemia-related biomarkers. We found that hemosiderin deposition was significantly correlated with the level of serum CRP (P = 0.045); however, no significant correlation was observed between hemosiderin deposition and serum IL-6 levels (P = 0.204). A non-significant positive correlation was observed between hemosiderin deposition and serum hemoglobin levels (P=0.09). Furthermore, no significant correlation was observed between hemosiderin deposition and serum iron levels (P = 0.799). In conclusion, hemosiderin deposition characteristically observed in PCD may be related to the inflammatory aggressiveness of the disease and could be used for its differential diagnosis.

Successful treatment of indolent T-cell lymphoproliferative disorder of the gastrointestinal tract (ITLPDGI) by chemotherapy is rare and watchful waiting is often performed for asymptomatic patients. We report a case of ITLPDGI successfully treated by involved field radiotherapy (IFRT). The patient presented with slow ITLPDGI localised to the stomach with mild symptoms. IFRT (30 Gy/20f) was administered, after which endoscopy revealed resolution of lesions and blood vessel appearance, and absence of proliferating abnormal lymphocytes was confirmed by biopsy. The patient remains lymphoma-free 1 year post-treatment. Although long-term follow-up and additional cases are essential for the evaluation of IFRT as a treatment option for localised ITLPDGL, complete remission after relatively low-dose IFRT is promising, particularly as this has been rarely achieved by chemotherapy.

Other iatrogenic immunodeficiency-associated lymphoproliferative disorders induced by immunosuppressive drugs, such as methotrexate (MTX-LPD), exhibit numerous pathological findings. We report the case of an 81-year-old Japanese woman diagnosed with MTX-LPD exhibiting two distinct pathological features from two different sites. Excisional biopsy of the left cervical lymph node revealed EBV-negative diffuse large B-cell lymphoma and biopsy of a pharyngeal ulcer revealed EBV-positive mucocutaneous ulcer. She was treated using an R-CHOP regimen and maintained complete remission for years. This case demonstrates the heterogeneous pathology of MTX-LPD and suggests the necessity of multiple biopsy.