[Clinicopathological features and prognosis of aggressive natural killer-cell leukemia: an analysis of 27 cases]

Objective: To investigate the clinicopathological features, diagnosis, and prognosis of aggressive natural killer-cell leukemia (ANKL). Methods: A retrospective analysis was conducted on 27 ANKL patients treated at the First Affiliated Hospital of Nanjing Medical University from 2014 to 2024. Their clinical data, histomorphology, and immunophenotype were reviewed. Kaplan-Meier analysis was used to evaluate the overall survival (OS), and COX regression analysis was performed to identify prognostic factors affecting OS. Results: Among the 27 patients, 18 were male and 9 were female, with a male-to-female ratio of 2∶1. The age ranged from 15-75 years, with a median age of 42.0 (28.5, 54.5) years. Fever and splenomegaly were the most common signs and symptoms. Most patients presented with pancytopenia, coagulation abnormalities, and liver dysfunction; and all patients had elevated EBV loads. Microscopically, 16 cases showed marked to hypercellular bone marrow proliferation, with predominant interstitial infiltration (15 cases, 55.6%), followed by sinusoidal infiltration (3 cases), diffuse infiltration (6 cases, 22.2%), mixed infiltration (interstitial and focal, 3 cases, 11.1%), focal infiltration (2 cases, 7.4%), and nodular infiltration (1 case, 3.7%). The proportion of tumor cells among nucleated cells ranged from 2% to 80%, with a median of 30%. The tumor cells displayed variable morphology. Hemophagocytosis was observed in 23 cases. Immunohistochemistry revealed that all cases expressed CD56, with mostly expressing cytotoxic molecules (granzyme B, TIA-1). The Ki-67 proliferative index ranged from 50% to 90%. CD56-EBER dual staining showed that NK cells were the primary targets of the virus. Reticulin staining showed increased fibrosis. By flow cytometry, all cases were positive for CD2 but negative for surface CD3 (sCD3), CD4, CD5 and CD57. Among them, 21 cases (95.5%) exhibited a typical phenotype of strong CD56 expression (CD56str+) with CD16 negativity (CD16-), while only one case (4.5%) showed CD16 positivity (CD16+) with dim CD56 expression (CD56dim). In killer-cell immunoglobulin-like receptor (KIR) analysis, 6 out of 17 patients (6/17) demonstrated monoclonal expression, including CD158a (4/6), CD158i (1/6), and CD158e (1/6); the remaining 11 cases (11/17) showed complete absence of KIR expression. All tested cases (17/17) were negative for T-cell receptor (TCR) protein expression. Follow-up period was from 257 days, 1 patient was lost to follow-up, and the remaining 26 patients died. Kaplan-Meier analysis revealed that OS was significantly longer in patients who received chemotherapy compared to those who did not (P<0.05). Univariate Cox proportional hazards model analysis indicated that age, bone marrow proliferation, proportion of tumor cells among nucleated cells, absolute neutrophil count, platelet count, and triglycerides and bilirubin levels significantly affected OS (P<0.05). Multivariate COX regression analysis identified triglycerides and bilirubin levels as independent prognostic factors for OS. Conclusion: Aggressive natural killer-cell leukemia is a rare lymphoid malignancy with very poor prognosis. Tumor cells exhibit significant morphological variation, and bone marrow infiltration patterns are diverse. Accurate recognition, early diagnosis, and timely chemotherapy are critical to improving the prognosis of patients with ANKL.