Aggressive NK-cell leukaemia and extranodal NK/T-cell lymphoma are two distinct diseases that differ in their clinical presentation and cytogenetic findings

Abstract

Aims

Distinguishing between aggressive NK-cell leukaemia (ANKCL) and extranodal NK/T-cell lymphoma (ENKTCL) with secondary bone marrow involvement is challenging, as they are rare bone marrow NK/T-cell neoplasms and share similar features.

Methods and results

We studied bone marrow NK/T-cell neoplasms by classifying them into those with no extramedullary mass (group 1, 8 cases) and those with extramedullary mass (group 2, 13 cases). Both groups showed similar clinical presentations and pathological features. Fever and cytopenia were the most common clinical presentations in both groups. The neoplastic cells varied from small and relatively monotonous cells to large pleomorphic cells. In six cases (2 in group 1 and 4 in group 2), the neoplastic infiltrate was inconspicuous, consisting of ≤10% of marrow cells in the interstitium, which were hardly identified by H&E stain alone. Nearly all patients were rapidly fatal no matter the neoplastic infiltrate volume. All the patients in group 1 fulfilled the WHO 2017 diagnostic criteria of ANKCL and their survivals were significantly worse than those of the group 2 patients (P = 0.035). In addition, group 1 patients were significantly associated with chromosome 7 abnormalities. Chromosome 6q deletion, commonly reported in ENKTCL, was seen in two of our group 2 patients, and was not observed in any of our group 1 patients.

Conclusion

ANKCL with no extramedullary mass should be distinguished from ENKTCL with bone marrow involvement as the former showed distinct outcome and genetic features.

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