Lipomas have characteristic structural chromosomal rearrangements of 12q13-q14.

Cytogenetic analysis was performed in 10 consecutive lipomas; 6 had typical benign histology whereas four had foci of atypia. Three tumors had supernumerary ring chromosomes, 6 had different balanced rearrangements, and one had a normal karyotype. Chromosome 12 was involved in 5 of the balanced rearrangements and, although less certainly, in all the ring chromosomes, with breakpoints localized to 12q13 or q14. The other rearranged chromosomes were numbers 2, 3, 7, 8, 11, 17 and 22. These results demonstrate the non-random involvement of chromosomal region 12q13-q14 in benign lipogenic tumors. The combined data from this and previous studies on benign and malignant lipogenic tumors indicate that different levels of cytogenetic specificity exist within this group of neoplasms. We suggest that myxoid liposarcoma development requires the recombination of 2 specific chromosomal bands (12q13 and 16pII), whereas for some types of benign lipogenic tumors structural changes in 12q13-q14 may be sufficient for neoplastic growth.