Large Granular Lymphocyte (LGL) disorders: A comparative study of T vs Natural Killer (NK) variants

MA Neben, BS,a WG Morice, MD,PhD,b PJ Kurtin, MD,b CA Hanson, MD,b RL Phyliky, MD,c A Tefferi, MDc

a Mayo Medical School, Rochester, MN United States b Division of Hematopathology, Mayo Clinic, Rochester, MN c Division of Hematology and Internal Medicine, Mayo Clinic, Rochester, MN

Aim To compare the clinical manifestations, laboratory features, bone marrow immunohistochemistry, and killer inhibitory receptor (KIR) expression patterns of T and NK- LGL. Methods We retrospectively identified 60 patients with either NK (11 patients) or T (49 patients) LGL disorders seen at the Mayo Clinic between 1984 and 1992. Bone marrow specimens from 32 T- and 9 NK-LGL patients were immuno-stained for CD8, granzyme B, and TIA-1. KIR expression pattern of 13 T- and 7 NK-LGL patients was determined by flow cytometry. Results T-LGL patients presented with a lower hemoglobin value (median 10.4 g/dL) and a higher incidence of both symptoms (74%) and palpable splenomegaly (35%) compared to patients with NK-LGL (median 12.4 g/dL, 44%, and 6%, respectively). Bone marrow examinations showed a higher incidence of CD8-positive lymphocyte clusters (84% vs 44%) and CD161 expression (83% vs 29%) in T vs NK LGL. Clonally restricted KIR expression patterns were seen in 1 of the 7 NK cases (14%) and 3 of the 13 T cases (23%). All the remaining T and NK cases showed a complete loss of KIR expression. Conclusions The current study suggests that T- and NK-LGL disorders are similar in most aspects including KIR expression patterns. A larger number of patients is needed to validate the apparent clinical differences observed in the current study. On the other hand, bone marrow immunohistochemistry reveals distinct histological features that distinguish the two disorders.

KEY WORDS: killer Inhibitory Receptor, Bone Marrow Immunohistochemistry.

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Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Paris, France; February 9 - 12, 2002; in the section on Molecular Pathology.