Asymptomatic T-cell large granular lymphocyte leukemia with an unusual immunophenotype

Hemophagocytic syndrome associated with large granular lymphoma in an adult dog

Hemophagocytic syndrome (HPS) is a rare disorder characterized by dysregulation of the immune response resulting in uncontrolled activation of macrophages with exacerbated phagocytosis of host cells. In dogs, the criteria for diagnosis include the presence of pancytopenia or bicytopenia in the peripheral blood and >2% hemophagocytic macrophages in bone marrow aspirates. When HPS is associated with lymphoma, it is called lymphoma-associated hemophagocytic syndrome (LAHS). Here, we present a case of a 4 ½-year-old female spayed Old English Mastiff that presented with severe thrombocytopenia, mild anemia, mild to moderate leukopenia, and large granular lymphocytes (LGLs) in the peripheral blood. The patient had enlarged lymph nodes with many LGLs seen cytologically, leading to the interpretation of LGL lymphoma. Bone marrow displayed numerous LGLs that stained strongly for CD3 but did not show immunoreactivity to CD4 or CD8, and PCR for antigen receptor rearrangement analysis confirmed a clonal T-cell receptor gamma gene rearrangement. The presence of ~3.5% hemophagocytes present on the bone marrow evaluation raised concern for HPS and, more specifically, LAHS. HPS and LAHS are challenging to diagnose and require many criteria to be fulfilled before a definitive diagnosis can be made; the low number of cases in the literature makes this even more challenging in dogs. This case represents secondary LAHS due to LGL lymphoma in a dog.

Atypical Presentation of T-Cell Large Granular Lymphocytic Leukemia Mimicking Pleural Malignancy on 18F-FDG PET/CT

T-cell large granular lymphocytic leukemia is a rare form of leukemia, caused by clonal proliferation of cytotoxic T-cells, characterized by modest lymphocytosis and cytopenias of other lineage with hepatosplenomegaly and relatively rare lymph nodal involvement. Involvement of other organs is extremely rare. It is predominantly an indolent disease and most of patients remain asymptomatic for a long period. We present a rare case of aggressive form (CD56 positive) of large granular lymphocytic leukemia with atypical presentations mimicking pleural malignancy on F-FDG PET/CT.