Case Number : Case 2226 - 20 December 2018 Posted By: Raul Perret

I see a lobulated adipocyte proliferation with many spindle cells, myxoid areas and entrapped skeletal muscle fibers. Rare mitotic figures are seen, Although I did not appreciate clear cut lipoblasts, my favored spot is lipoblastoma. 

Yes. Lipoblastoma.

Agree with lipoblastoma. I miss some more myxoid matrix, but I can´t see any other diagnosis.

Fully agree with my Colleagues (some myxoid Matrix in fig7 and lipoblast in the last one ). 

Dear colleagues, yes this was a case of lipoblastoma/lipoblastomatosis. Probably in the spectrum of the latter due to the irregular infiltration of skeletal muscle. The main point here is that almost any adipose tumor presenting in infants is a lipoblastoma, even without lipoblasts aka "maturing" or" mature" Lipomas do exist but they are extremely rare (septation goes against a dx of lipoma in this age group). Malignant adipocytic tumours are exceptional in infants and are mainly repredented by myxoid liposarcomas.  Lipoblastoma has a recurring molecular anomaly consisting of a plag1 rearrangement, usually with HAS2 or COL1A2, that can be reliably demonstrated by FISH analysis. Lipoblastoma is a completely benign neoplasm, recurrences may be seen, mainly in the cases of lipoblastomatosis. Good job everyone for spot on diagnosis, wish you a merry Christmas and a happy new year

Another great case Raul.