Lipoma vs. Liposarcoma: How to Tell the Difference

I get asked this question a lot. 

How does fat from a lipoma look different than a liposarcoma?

Well, wonder no more, because I have a handy little graphic I whipped up to share with you!

In a lipoma, the adipocytes look...happy.

They are big cells with a single, clear cytoplasmic vacuole. Their nucleus is itty bitty and off to the side. There is no criteria of malignancy to speak of.

Now, compare that to its evil, malignant twin, the liposarcoma.

Liposarcomas are u-g-l-y.

In fact, they don't really resemble adipocytes at all anymore.

Rather, they have wispy to ovoid borders and a moderate to large amount of cytoplasm that contains many small, discrete vacuoles. Their nuclei are large, and they often have prominent nucleoli. Criteria of malignancy is often plentiful.

Important cytologic things to remember:

- Liposarcomas don't always exfoliate well, so you can't rule this out even if you don't see the ugly cells on FNA.

- Normal, subcutaneous fat will look just like fat from a lipoma.

-Infiltrative lipomas will look just like "happy" fat, but have a different clinical course.

Hopefully now you can see just how different these two neoplasms look cytologically!