The 2;5 chromosomal translocation occurs in most anaplastic large-cell non-Hodgkin's lymphomas arising from activated T lymphocytes. This rearrangement was shown to fuse the NPM nucleolar phosphoprotein gene on chromosome 5q35 to a previously unidentified protein tyrosine kinase gene, ALK, on chromosome 2p23. In the predicted hybrid protein, the amino terminus of nucleophosmin (NPM) is linked to the catalytic domain of anaplastic lymphoma kinase (ALK). Expressed in the small intestine, testis, and brain but not in normal lymphoid cells, ALK shows greatest sequence similarity to the insulin receptor subfamily of kinases. Unscheduled expression of the truncated ALK may contribute to malignant transformation in these lymphomas.

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We describe here the clinical and pathologic features associated with a specific translocation, t(2;13), in alveolar rhabdomyosarcoma. Tumor specimens from 14 patients with a t(2;13)-positive alveolar rhabdomyosarcoma were studied for cytogenetic-clinicopathologic correlations. Three patients had occult primary tumors; nine patients had primary tumors of the trunk (mediastinal, pelvic, or rectal). The presence of the t(2;13) was ascertained from examination of tumor involved bone marrow in ten patients who had widespread metastatic disease at the time of diagnosis. Marrow involvement was so extensive in three cases that they were initially diagnosed as acute leukemia. Response to therapy was poor, with only five patients achieving a complete response. Twelve patients have died of their disease at a median survival time of 6 months from diagnosis and one is living with recurrent disease; only one patient survives free of disease.