This morphologic evidence is further supported by molecular genetic data, showing recurrent TGFBR3 and/or MGEA5 rearrangements in both hemosiderotic fibrolipomatous tumor and pleomorphic hyalinizing angiectatic tumor.
Unlike t(1;10), BRAF rearrangements were only found in MIFS but not in 6 hemosiderotic fibrolipomatous tumor (HFLT) lacking TGFBR3-MGEA5 fusions (including 2 pure HFLT, 2 hybrid HFLT-MIFS, and 2 associated with pleomorphic hyalinizing angiectatic tumors).
TGFBR3 and MGEA5 rearrangements have also been reported in hemosiderotic fibrolipomatous tumor (HFLT), in pleomorphic hyalinizing angiectatic tumor (PHAT), and in rare tumors allegedly showing features of both HFLT and MIFS (hybrid HFLT-MIFS).
Cases of PHAT (all containing areas of HFLT) (N=10), HFLT (N=7), MIFS (N=6), hybrid HFLT/MIFS (N=3), and PHAT-like undifferentiated pleomorphic sarcomas (N=7) were retrieved from our institutional and consultation archives and analyzed for TGFBR3 and MGEA5 rearrangements using a break-apart probe strategy for FISH.
Although PHAT is still poorly characterized at the genetic level, there is a potential genetic overlap with two other soft tissue tumors: myxoinflammatory fibroblastic sarcoma (MIFS) and hemosiderotic fibrolipomatous tumor (HFLT); MIFS and HFLT share a characteristic t(1;10)(p22;q24) with breakpoints in the TGFBR3 locus on chromosome 1 and near the MGEA5 locus on chromosome 10.