Ab130405

Paraffin-embedded section (3 µm thick) were dewaxed in xylene and heated in 0.01 M sodium citrate buffer (pH = 6.0) in a microwave at 60 °C for 20 min for antigen retrieval. Tissue sections were then blocked in 0.3% H₂O₂ for 10 min to remove endogenous peroxidase activity, followed by incubation with primary antibody against CD4 (1:1000; ab288724, abcam, Cambridge, MA, USA), CD20 (1:50; ab78237, abcam), or CD138 (1:100; ab130405, abcam). The target was visualized with a DAB staining kit (GK600710, Gene Tech, Shanghai, China).

The tumor tissue specimens were fixed in a 10% formalin solution, followed by embedding in paraffin and staining with hematoxylin–eosin. The diagnosis of solitary plasmacytoma and MM was determined based on the established International Myeloma Working Group (IMWG) criteria.
² (link) For immunohistochemistry, a representative tissue block was selected and subjected to the avidin‐biotin complex horseradish‐peroxidase method. Primary antibodies against CD138 (Abcam, ab130405), kappa light chain (Abcam, ab227654), lambda light chain (Abcam, ab195573), and Ki‐67 (Abcam, ab15580) were applied according to the manufacturer's instructions. Two pathologists independently evaluated all stained sections without any knowledge of the corresponding clinical data. In cases of discordance, the staining results were reviewed by the observers until a consensus was reached.