Expression patterns of the LPP–HMGA2 fusion transcript 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 HMGA2–LPP fusion gene the most frequent fusion gene in human tumors. We analyzed 11 PCHs with a t(3;12)(q27∼28;q14∼15) for the expression of the LPP–HMGA2 fusion transcript. In a previous study, all of these tumors were shown to express the HMGA2–LPP fusion transcript, composed of exons 1–3 of HMGA2 and exons 9–11 of LPP. In the present study, reverse transcriptase-polymerase chain reaction revealed the expression of the reciprocal fusion transcript in 8 of 11 cases. In all positive tumors, the reciprocal fusion transcripts had the same structure, namely, exons 1–8 of LPP and exons 4–5 of HMGA2 encoding a protein composed of the proline-rich region and the first LIM-domain of LPP and the acidic tail of HMGA2. To our knowledge, this is the first report of the expression of the LPP–HMGA2 fusion transcript in a series of PCHs. Its frequent occurrence in PCHs indicates the absence of a larger deletion of the LPP locus accompanying the translocation, such as has been described in a lipoma. Thus, based on this one finding, a role of LPP–HMGA2 in PCH should be considered.