Case Number : Case 2346 - 13 June 2019 Posted By: Raul Perret

2005 tumor=Pleomorphic liposarcoma

2019 tumor=High grade liposarcoma, NOS. Not a spindle cell well differentiated liposarcoma.

2019: dedifferentiated liposarc?

Dedifferentiated lipossrcoma

On 12/06/2019 at 14:45, vincenzo said:

2005 tumor=Pleomorphic liposarcoma

2019 tumor=High grade liposarcoma, NOS. Not a spindle cell well differentiated liposarcoma.

Yes, agree.

At least until IHC or Molecular proven otherwise.

2005: Looks like a pleomorphic liposarcoma.

2019: Some kind of high-grade sarcoma. But I do not see any evidence of adipocytic differentiation, at least in this core biopsy.

If the tumor was a pleomorphic sarcoma in 2005, then the new tumor in 2019  cannot be a dedifferentiated LS because per definition a dedifferentiated LS arises from an atypical lipomatous tumor / well-diff. LS (to wit, a LS with MDM-2 and CDK-4 abnormalities). But pleomorphic LS does not have MDM-2 or CDK-4 mutations or amplifications.

So agree with additional IHC and molecular studies.

A local recurrence from a high-grade pleomorphic LS 14 years later is definitely very unusual. Maybe a radiation-induced sarcoma, particularly that I do not see any definitive adipocytic differentiation in the new tumor.

Dear all, 2005 tumor was wrongly classified initially. It turned out to be a dedifferentiated liposarcoma with homologous "lipoblastic differentiation" (20588177). 2019 was a recurrence of the same tumor.
2 main lessons from this case:

1- If previous history of cancer always rule out a local recurrence before considering a second primary.
2- If morphologically malignant (atypical cells, necrosis, Mitosis) ➕ lipoblasts don't forget staining for MDM2

Take also into account that clinical discordance should draw our attention as Pleomorphic liposarcoma is a highly aggressive form of sarcoma and long-term survival is very rare. 
Thanks for participating 

Dear Raul,

2005 case is, morphologically, a pleomorphic liposarcoma, but with CPC and MDM2 we can better define it a dedifferentiated liposarcoma. 

2019 case is a liposarcoma, NOS, without other clinical or pathological informations. So we can't know if that one could be a recurrence or a second primary.

1 main lesson from this case:

Don't make a diagnosis without any CPC and I totally agree!!!

...BUT this a "spot diagnosis" web site!

Thanks for this interesting case.

26 minutes ago, vincenzo said:

Dear Raul,

2005 case is, morphologically, a pleomorphic liposarcoma, but with CPC and MDM2 we can better define it a dedifferentiated liposarcoma. 

2019 case is a liposarcoma, NOS, without other clinical or pathological informations. So we can't know if that one could be a recurrence or a second primary.

1 main lesson from this case:

Don't make a diagnosis without any CPC and I totally agree!!!

...BUT this a "spot diagnosis" web site!

Thanks for this interesting case.

Sorry Vincenzo. Did not get your point, I thought this was a good case for illustrating the difficulties of real life pathology. 2005 tumor is a dedifferentiated liposarcoma, 2019 tumor is recurence of the same lesion. Dont forget that dedifferentiated liposarcoma is extremely polymorphous morphologically. Furthermore, I would not recommend currently using the term liposarcoma NOS, in any case. That is an inaccurate term that does not provide information on the aggressiveness of the tumor. With current understanding and  the use of ancillary techniques we arrive at correctly classifying adipous sarcomas in 100% of cases

Maybe I did not explain correctly the sequence. When I received the 2019 biopsy, I did not know that the previous case was wrongly diagnosed initially. I subsequently checked the previous case, performed MDM2 IHC on both tumors and confirmed MDM2 amplification by FISH. The idea was not to "trick" people just sharing cases

Great discussion and very instructive points from all the comments. 

Most important lesson: always review the previous pathology material.