Ig-gene and T-cell receptor gene rearrangements in a secondary, mono-histiocytic malignancy.

In 1984, a 21-year-old male was diagnosed with an acute lymphoblastic leukemia of pre-B cell type. Treatment with chemotherapy, including alkylating agents and prophylactic radiotherapy to the central nervous system, induced a complete remission. In June 1990, a biopsy from a supraclavicular node revealed a malignancy of mono-histiocytic type with erythrophagocytosis. Soon thereafter bone marrow involvement was found. No remission was achieved and the patient died in December 1990. DNA from bone marrow and lymph node obtained 1990 showed clonal rearrangements of both the immunoglobulin heavy-chain gene and the T-cell receptor gamma chain gene. This unusual case illustrates a typical secondary malignancy proven to be separate from the primary neoplasm judged by morphological appearance, immunophenotype and cytogenetic constitution. Coexistent clonal rearrangements of immunoglobulin and T-cell receptor genes have been reported in acute non-lymphoblastic leukemias and notably in cases expressing TdT, interpreted as a predominant lymphoid commitment of the tumor cells. In the present case, however, the malignant cells had a differentiated phenotype and showed erythrophagocytosis, indicating a more mature mono-histiocytic cell type. However, also CD3 expression was found by immunohistochemistry of frozen sections which might indicate a biphenotypic malignancy.