A 32-year-old white woman was admitted with a diagnosis of T lymphoblastic lymphoma and a bone marrow and peripheral blood cytology that was suggestive of a myeloproliferative syndrome (MPS). In addition, islets of myeloid precursors were found in the lymph node where the lymphoma had been diagnosed. Cytogenetic examination was negative for the Philadelphia chromosome (Ph) as well as the RT-PCR for bcr/abl rearrangement, but surprisingly a t(8;13)(q10;p10) was detected. To our knowledge, this translocation has not been reported in such a clinical setting. The patient was treated for the lymphoblastic lymphoma and underwent autologous bone marrow transplantation. She has been in complete remission since induction chemotherapy with a Karnofsky score of 100%. The difficulty of classifying this case is discussed.