New PLAG1-fusion transcripts in the spectrum of pediatric fibrotic, lipofibrotic, and mature lipomatous tumors

The histomorphology of liboblastoma is highly variable and comprises different patterns that are found admixed or in pure form within a tumor. The most important features - mature lipomatous, fibrotic, lipofibrous, and myxoid - overlap with the histomorphology of several other pediatric tumor entities. Regarding the morphologic overlaps, molecular diagnostics with identification of fusion transcripts involving PLAG1 or HMGA2 is essential to identify lipoblastomas. This paper describes the diagnostic procedure in general and two new fusion transcripts of lipoblastoma, MEG3-PLAG1 and COL1A1-PLAG1. In conclusion, the algorithm to diagnose lipoblastomas among this group of pediatric fibrotic, lipofibrous and mature lipomatous tumors essentially includes histomorphology, immunohistochemistry, and molecular diagnostics.