Mapping of the translocation breakpoints of primary pleomorphic adenomas and lipomas within a common region of chromosome 12.

Recent molecular cytogenetic analysis of uterine leiomyoma cell lines with chromosomal aberrations of 12q14-q15 have indicated that the chromosome 12 breakpoints cluster in a 445-kb region designated ULCR12 (uterine leiomyoma cluster region of the chromosome 12 breakpoints). Here we report the results of FISH studies of five primary pleomorphic adenomas and six primary lipomas and established cell lines of these tumor types characterized by translocations involving the chromosomal segment 12q13-q15. The results reveal that for nearly all tumors and cell lines analyzed, the chromosome 12 breakpoints map within a 350-kb region included in ULCR12, despite the previous cytogenetic assignment of the breakpoints to different bands of that region. In some cases the primary material and additionally analyzed cell lines allowed an even more precise localization of the breakpoints to less than 100 kb. Furthermore, a previously hidden translocation of ULCR12 in one primary tumor could be detected by FISH.