Characteristic appearances of the bone marrow in T-cell large granular lymphocyte leukaemia

To augment the limited literature on bone marrow (BM) appearances in T-cell large granular lymphocyte (LGL) leukaemia and to identify a histological signature to aid in diagnosis of this condition.

A descriptive analysis of the histology of the BM in T-cell LGL leukaemia was performed (n = 38). Antibodies against CD3, CD4, CD5, CD8, CD16, CD56, CD57 and CD20 or CD79a were employed. Antibodies against CD68 (macrophages) and CD34 (sinusoids) were also included. BM was normocellular or hypercellular in the majority of cases, with interstitial lymphoid infiltration in 97%. Lymphoid nodules were present in 55% and intrasinusoidal permeation in 58%. Apoptotic figures and haemosiderin deposition were common. All cases showed trilinear haematopoiesis with normal or increased megakaryopoiesis and erythropoiesis, but normal/reduced myelopoiesis. Reticulin was increased (Grade II-III). Immunohistochemistry revealed interstitial infiltration in all cases and helped to identify lymphoid nodules in two-thirds of cases. Preferential localization of CD8+ T lymphocytes to the interstitium and CD4+ T lymphocytes to the periphery of CD20+ B-cell nodules was seen in almost 90% of cases.

Nodules with non-clonal B-cell centres surrounded by CD4+ cells, with interstitial CD8+ cells, are a characteristic finding in T-cell LGL leukaemia and may represent a histological signature for this condition.