Immunohistochemistry (IHC) and prognostic analysis of PRDM1 in extranodal NK/T-cell lymphoma, nasal type (EN-NK/T-NT) cases. Examples of IHC analysis of PRDM1 in EN-NK/T-NT specimens and control samples. (A) PRDM1 staining in the nuclei of tumour cells was observed in approximately 50% of tumour cells in 1 case of EN-NK/T-NT; most cells had moderate to weak nuclear staining. (B) PRDM1 was expressed in approximately 10% of tumour cells in 1 case of EN-NK/T-NT. (C) No PRDM1 staining was detected in 1 case of EN-NK/T-NT. In the control cases, strong nuclear PRDM1 immunostaining was observed in plasma cell myeloma (D), the epithelium and germinal centre of the tonsil (E), and the squamous epithelium of the nasal mucosa (F) (all by IHC; A, B, C, and F are shown at 400× magnification; D and E are shown at 200× magnification). (G) and (H) Kaplan-Meier survival analysis demonstrated that PRDM1 expression predicted a favourable effect on overall survival (OS) and failure-free survival (FFS) of EN-NK/T-NT patients (P = 0.084 and P = 0.042, respectively).