LAUSR

A 16-year-old female presented with fatigue, easy-bruising and unintentional weight loss and was found to have lymphadenopathy and hepatosplenomegaly. On further investigation, she had leucocytosis, anaemia, thrombocytopenia and a mediastinal mass. Bone marrow clot sections and an aspirate showed predominance of blast cells. Scattered rosettes and gland-like structures lined by blast cells were present in the clot sections (upper left; haematoxylin and eosin stain; upper right; Periodic acid-Schiff stain, 940 objective) and films (lower left; Wright–Giemsa stain, 9100). By immunohistochemistry, the blasts, including those lining the gland-like structures, were positive for cytoplasmic (c) CD3 (lower right, 940) and terminal deoxynucleotidyl transferase (TdT). There was no positivity for neuroendocrine markers or cytokeratin. Flow cytometry showed T lymphoblasts (96.6%) positive for CD1a, cCD3, CD4 (weak), CD5, CD7, CD45 (weak) and TdT, and negative for CD2, membrane CD3, CD8, CD19, CD33, CD34, cCD79a and myeloperoxidase, indicating T-lymphoblastic leukaemia/lymphoma (T-ALL). Molecular studies showed clonal T-cell receptor gene rearrangement. The karyotype was normal. Rosettes and gland-like structures formed by lymphoblasts are highly unusual features of unknown significance in acute lymphoblastic leukaemia although they are commonly seen in solid malignancies including neuroblastoma, retinoblastoma and Ewing’s sarcoma. This case illustrates the importance of ancillary studies including immunophenotyping in addition to morphology for accurate diagnosis.