A rare chimeric TLS/FUS-CHOP transcript in a patient with multiple liposarcomas: a case report.

Myxoid liposarcomas harbor a unique and specific t(12;16)(q13,p11) chromosomal translocation. The breakpoint has recently been identified, and involvement of the TLS/FUS gene on chromosome 16 and the CHOP gene on chromosome 12 was demonstrated. We report a case of a 45-year-old woman who developed multiple malignant lipomatous tumors of unknown origin and myxoid/round cell histology at different locations. To examine the diagnostic potential of this translocation and to develop a hypothesis on the origin of the tumors, we used cytogenetic and molecular cytogenetic methods (reverse transcription polymerase chain reaction, RT-PCR). We identified a chimeric RNA transcript in the second recurrence in the thigh/groin, as well as in another tumor in the mediastinum, which has an additional sequence of 33 bp, known as fusion transcript type III. Cytogenetic analysis of another tumor in retroperitoneal space revealed a rare type of unbalanced translocation der(16)t(12;16). We hypothesize that these tumors are metastases rather than multicentric tumors. The detection of the chimeric message in the present case is not only useful for differential diagnosis, but also for analyzing the origin of multiple neoplasms.