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Introduction

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Large granular lymphocyte leukaemia (LGLL) may be of T lineage or natural killer (NK) lineage. NK-cell leukaemia may be indolent or aggressive [1-4]. Recognition of indolent NK-cell leukaemia is complicated by the fact that markers of clonality have not been readily available and have often not been employed, leading to uncertainty as to whether the condition is reactive or leukaemic in nature. Recognition of aggressive cases is more straightforward and it is this group that has been designated aggressive NK-cell lymphoma in the World Health Organization (WHO) classification. Aggressive NK-cell lymphoma is more common in Far East Asia than in the West and there is a strong association with the Epstein-Barr virus.

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Clinical features

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Some cases are indolent while others have aggressive disease with constitutional symptoms and often abnormal coagulation. There may be hepatosplenomegaly and lymphadenopathy.

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Haematological and pathological features

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The number of circulating neoplastic cells may be low or high. Indolent cases have cells resembling normal large granular lymphocytes and similar to the neoplastic cells of T-lineage LGLL. Patients with aggressive disease have neoplastic cells that are more atypical than those of T-lineage LGLL (Figures 19.1,19.2,19.3); they are granular lymphocytes that may be increased in size and have moderately basophilic cytoplasm or irregular or hyperchromatic nuclei. Anaemia, neutropenia and thrombocytopenia are common in patients with aggressive disease and in these patients the bone marrow shows not only infiltration but often also haemophagocytosis.

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Figure 19.1

Peripheral blood film from a patient with NK-lineage large granular lymphocyte leukaemia showing atypical large granular lymphocytes, many of which are larger than their normal equivalent and have lobulated nuclei. Romanowsky, x 100 objective.

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Figure 19.2

Ultrastructure of a neoplastic cell from a patient with NK-lineage large granular lymphocyte leukaemia showing cytoplasmic granules and a somewhat irregular nucleus with a nucleolus. Lead nitrate and uranyl acetate stain.

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Figure 19.3

Bone marrow film from a patient with NK-lineage large granular lymphocyte leukaemia showing pleomorphic large granular lymphocytes, with irregular nuclei and nucleoli. Romanowsky, x 100 objective.

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Immunophenotype

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The neoplastic cells are NK cells, not expressing CD3 but usually expressing CD2, CD56 and CD94 [5-7]. CD11c and CD16 may be expressed but CD57 is usually negative. CD158 may be expressed with a monoclonal pattern of expression - CD158a, CD158b or CD158e restricted or CD158 not expressed [6]. On immunohistochemistry, expression of cytoplasmic CD3ε chain may be detected; it should be noted that polyclonal antibodies used to detect CD3 in tissue sections cross-react with the zeta chain of the CD3 expressed in ...

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