Multifocal myxoid liposarcoma--metastasis or second primary tumor?: a molecular biological analysis.

The classification of multifocal myxoid/round cell liposarcoma, which is defined as tumor presentation in at least two separate sites before manifestation in the lungs, as either metastasis or as a second primary tumor, has essential clinical consequences. Genetically, myxoid/round cell liposarcoma is characterized by t(12;16)(q13;p11) or t(12;22)(q13;q12), and various exon fusion transcripts are described with varying incidences, which permits their use as markers for clonality. Moreover, in solid tumors, analysis of loss of heterozygozity is valuable for clonality analysis.

Primary retroperitoneal myxoid/round cell liposarcoma is a nonexisting disease: an immunohistochemical and molecular biological analysis.

Almost all primary retroperitoneal liposarcomas can be classified as well-/dedifferentiated liposarcoma. Rarely, however, primary retroperitoneal liposarcoma is classified as myxoid/round cell liposarcoma, based on the presence of myxoid areas and vascular crow's feet pattern, which has resulted in a debate on the classification of liposarcoma in the retroperitoneum. Genetically, myxoid/round cell liposarcoma and well-/dedifferentiated liposarcoma are different diseases.