EXPRESSION OF RECIPROCAL FUSION TRANSCRIPTS OF THE HMGIC AND LPP GENES IN PAROSTEAL LIPOMA

Parosteal lipomas are rare benign neoplasms of adipose tissue that exh ibit a contiguous relationship with the periosteum. These lipomas of t he bone share some histopathologic features with their commonly occurr ing soft tissue counterparts. The latter are well-characterized cytoge netically, primarily by rearrangements involving chromosome region 12q 13-q15. In particular, translocations involving 12q13-q15 are prominen t, with chromosomal region 3q27-q28 as the most frequent translocation partner. Recently, we established that the genes HMGIC at 12q15 and L PP at 3q27-28 are affected by the 3;12-translocation and demonstrated that, as a direct result, HMGIC/LPP and LPP/HMGIC fusion transcripts a re expressed in soft tissue lipomas. In this study, cytogenetic and mo lecular analyses revealed similar findings in a parosteal lipoma. Spec ifically, a t(3;12)(q28;q14) was detected cytogenetically in a paroste al lipoma from a 51-year-old female and subsequently confirmed by FISH utilizing a chromosome 3 breakpoint spanning YAC probe and chromosome 12 breakpoint flanking cosmid probes. RT-PCR analysis showed expressi on of HMGIC/LPP and LPP/HMGIC fusion transcripts in this parosteal lip oma; nucleotide sequence analysis revealed that these transcripts are identical to those expressed in soft tissue lipomas characterized by a 3;la-translocation. These findings lend further support to a common h istopathogenesis between lipomas of soft tissue and parosteal origin. (C) Elsevier Science Inc., 1998.