Phenotypic and ultrastructural characterization of a medullary thymocyte acute lymphoblastic leukemia with cellular procoagulant activity

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Abstract
The phenotypic and ultrastructural characterization of the blast cells from a T‐cell acute lymphoblastic leukemia (T‐ALL) that was associated with disseminated intravascular coagulation (DIC) is described. The bone marrow blasts were considered to represent neoplastic medullary thymocytes and were acid phosphatase (+), terminal deoxynucleotidyl transferase (‐), acid alpha‐naphthyl acetate esterase (‐), E‐rosette (+) at 4°C and 37°C, Fc‐ and C3‐receptor (‐), and cALLA‐, la‐, 9.6+, OKT3+, OKT4+, OKT6+/‐, OKT8+, OKT10+. On transmission electron miscroscopic study, the predominant cell was 6 μm in diameter and possessed an irregular nucleus, moderate‐sized nucleolus, marginated heterochromatin, abundant Golgi elements and granules, and prominent intermediate filaments. The cells were analyzed with normal and factor‐deficient human plasmas and contained significant amounts of tissue factor‐like procoagulant activity. This is the first report of a well‐characterized medullary thymocyte T‐ALL in which DIC was an accompanying feature, and the first demonstration of tissue factor‐like procoagulant activity in acute lymphoblastic leukemia. In view of thrombohemorrhagic phenomena observed in association with other medullary thymocyte leukemias, these findings suggest that tissue factor‐like procoagulant activity may be a characteristic of medullary thymocyte‐derived lymphoid leukemias.