An identical HMGIC-LPP fusion transcript is consistently expressed in pulmonary chondroid hamartomas with t(3;12)(q27-28;q14-15).

The high frequency of the t(3;12)(q27-28;q14-15) in lipomas and pulmonary chondroid hamartomas (PCHs) makes the HMGIC-LPP fusion gene the most common fusion gene in a human tumor known so far. Nevertheless, there is no in-depth molecular analysis of the HMGIC-LPP fusion transcripts in PCHs. Certainly, a possible molecular variability of the HMGIC-LPP fusion may contribute to a better understanding of the histologic differences between lipomas and PCHs and the intratumoral histologic heterogeneity of PCHs. By RT-PCR and restriction analysis, we have investigated the HMGIC-LPP fusion transcripts in a series of 13 PCHs with t(3;12)(q27-28;q14-q15). HMGIC-LPP fusion transcripts of identical size were found in all PCHs tested. In all tumors investigated, the fusion transcripts had the same structure, i.e., exons 1 to 3 of HMGIC and exons 9 to 11 of LPP encoding a protein composed of three AT-hooks and two LIM-domains. Our results clearly show that neither the histologic differences between lipomas and PCHs nor the histologic heterogeneity of PCHs can be explained by a molecular diversity of the HMGIC-LPP fusion transcript. Copyright 2000 Wiley-Liss, Inc.