Case Number : Case 2088 - 7 June 2018 Posted By: Raul Perret

If the lesion is negative for keratin, desmin and the GMS stain does not show organisms in the areas shown in the last photo, I intend to classify as pleomorphic undifferentiated sarcoma.

There is definitively cytologic atypia in the lesion, maybe even severe. But i do not see any mitoses or necrosis (at least in the figures). So there is a discrepancy between the degree of cytologic atypia and the mitotic activity. Can the cytologic atypia a degenerative phenomenom in nature? I also see foamy histiocytes and I usually back off a little bit from malignancy when I see that. There are also dilated blood vessels. If the lesion is positive for S_100 protein and SOX-10, I would consider anscient schwannoma.

Anh has a good point. I would run S100, too.

Which feature does win here?

the curvilinear vessels of Myxofibrosarcoma or the ganglion-like cells of myxoinflammatory fibroblastic sarcoma or the Angietactic sand pleomorphic but without hyalinization features of Pleomorphic hyalinizing angiectatic tumor?  The age and the site but also th microscopy make me favor PHAT. 

I answered too soon. Here Anh wins. 

Actually if S-100 is negative, I would start considering PHAT or maybe lipidized fibrous histiocytoma (because of the location) or atypical fibrous histiocytoma. So we definitely need immunos. That's the fun part of this activity. We all learn something new every day.

S100, desmin, h-caldesmon, mdm2, negatives. CK focally positive, CD34 diffusely positive. What do you guys think?

EMA? loss of INI?The immunohistochemistry leans towards epithelioid sarcoma but there are many histyocytes

2 minutes ago, msofopoulos said:

EMA? loss of INI?The immunohistochemistry leans towards epithelioid sarcoma but there are many histyocytes

INI1 positive (retained). EMA negative

Cd31?

So why not a PHAT? Or the equivalent Hemosiderotic fibrohistiocytic lipomatous tumor?

29 minutes ago, vincenzo polizzi said:

 

This was a case of Superficial CD34+ fibroblastic tumor. This entity was reported initially by Carter et al. in 2014 (https://www.nature.com/articles/modpathol2013139). It is characterized by a superficial location, diffuse expression of CD34, frequent focal co-expression of CK, presence of spindle cells with ample glassy eosinophilic cytoplasm (which can be quite focal), atypical bizarre nuclei, areas of inflammation, xanthomization and minimal mitotic activity.

Differential diagnosis to consider are (as Vincenzo initially suggested) PHAT and myxoinflammatory fibroblastic sarcoma which can share many morphological and immunophenotypic features (they are probable entities related with superficial CD34+ fibroblastic tumor). In order to rule out the latter differentials we performed a CGH to evaluate if there were amplifications of VGLL3 (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3361892/), the test demonstrated a flat profile.

This tumor seems to be of intermediate malignancy and will be probably better characterized in the future by performing NGS based techniques like RNAseq and whole exome sequencing. I also think they are probably underrecognized due to recent description and the presence of less than 50 cases reported in the literature. I am lucky enough to have already diagnosed 2 cases in resection specimens and will probably receive a third one soon (suspected on biopsy). Thanks for the great comments.

Great case. Thanks for sharing.

Very great case Raul. Thanks. 

Great case! Thanks