Case Number : Case 2043 - 05 April 2018 Posted By: Raul Perret

Tough without immunos. My first thought is solitary fibrous tumor but I do not see the hemangiopericytoma-like vessels.  Still I would do STAT6. Also MUC 4 to rule out Evans tumor.

Deep fibrous histiocytoma

it is a bit difficult to be sure of the lineage of the cells without immunos but looking at the loubular appearance in pic 2 , I would also like to see a MUC4. 

Wow. This is a really interesting case. My spot: LGFMS. Muc4 could be useful. 

Thanks Raul for this nice case. 

Nodular fasciitis?

I thought of nodular fasciitis 

Thank you very much for the comments on this case. This is indeed a case of low grade fibromyxoid sarcoma, an entity first recognized by Dr. Evans and colleagues in 1987, initially considered benign until its metastatic potential was documented (this is one of the many tumors that tends to give late metastases).

This sarcoma usually develops in young patients and presents as a deep seated mass. The main histological features that suggest the diagnosis in this case are: alternating cellular density, slightly nodular and fascicular architecture, fibrous and slightly myxoid stroma (in this case pale/amphophilic areas),  spindle cells with low grade atypia and monomorphous hyperchromatic nuclei (typical of translocation-related sarcomas).

The diagnosis was confirmed by staining with MUC4 which is a highly sensitive and specific marker for this tumor. In France where I work presently, the demonstration of FUS/CREB3L1/2 fusion transcripts by RT-PCR or FUS rearrangements by FISH are not performed systematically for this type tumor if the clinical setting, morphology and phenotype are typical.  

The differential diagnosis includes desmoid tumors, intramuscular myxoma (cellular variant), myxoid neurofibroma, among others. When there is any doubt MUC4 should be performed. 

Concerning the differential of nodular fasciitis, it is important to mention that a deep location and a size of more than 3 cm are rarely/never seen in this entity. We really think twice before making a diagnosis of NF in our department if any of this 2 features are present  (and we will sometimes search for USP6 rearrangements to be sure).

Thank you once again for your great comments and the team of Dermpathpro for kindly inviting me to share some cases.

Here is the MUC4 stain that was performed in this case, remarking the nodularity that was mentioned by some of the colleagues. Have a great weekend. And if there are any questions or remarks please let me know. 

Congrats Vincenzo. Thanks Raul for your elaborate explanation.

Thanks Anil

Great case Raul!

Well done Vincenzo!

Congratulations to Raul as a case presenter of Dermpathpro.com

i really enjoy your cases.

i was busy for a while,now i try to be more present!