Adult T-cell leukemia/lymphoma with an unusual CD1a positive phenotype

Acute T-cell leukemia lymphoma (ATLL) tumor cells generally express CD2/CD3/CD5, but lack CD7. These T cells are usually CD4+CD8- and strongly express CD25, although some variability in this basic pattern may be found. Here we report a case with a very unusual CD1a positive phenotype.

Samples from peripheral blood, bone marrow aspirate, lymph node, and cerebrospinal fluid obtained from a 45-year-old male patient with a T-cell lymphoproliferative disorder were immunophenotyped by multiparametric flow cytometry. Analysis of HTLV-I genome integration in tumoral cells was performed by PCR.

Neoplastic T cells were cCD3, CD2/CD5/CD30/CD25, and CD1a positive, but CD3/CD7/CD4/CD8/CD34/CD10/TdT negative. Serology and integration of HTLV-I were positive.

To the best of our knowledge, CD1a expression has not been previously described in this entity. Its detection raised the differential diagnosis with acute T lymphoblastic leukemia. The rest of the phenotypic markers, the morphology of the neoplastic cells, and the demonstration of HTLV-I genome integration provided the final diagnosis.