Bone marrow biopsy of a 42-year-old man presenting with hepatosplenomegaly, pancytopenia and anaemia (Hb 10·5 g/dl, white blood cells 1·1 × 109/l, platelet 60 × 109/l) revealed sinusoidal infiltration of medium-sized lymphoid cells with moderately clumped chromatin and a rim of pale cytoplasm (top); immunohistochemistry showed positivity for CD45RO (bottom) and CD3, and negativity for B-cell antibodies. On morphological and immunohistochemical grounds, a diagnosis of hepatosplenic T-cell lymphoma of possible γ/δ origin was made. Confirmation of T-cell receptor δ+ was made by flow cytometry study on circulating cells. Pentostatin treatment was followed by full haematological recovery. Six months after diagnosis, a second bone marrow biopsy displayed an almost complete disappearance of sinusoidal lymphomatous infiltration.