thank you for this difficult case.
the feature of rhabdoid like cells make me to thick about malignant extrarenal rhabdoid tumor, so if the intracytoplasmic globules is present in some of tumoral cells and positivity for CK and EMA , I think we must think of this tumor also

Proximal epithelioid sarcoma?

It would be nice to know the immunopanel employed and which of them were positive.

What type of RMS do you suggest here?
i think pleomorphic is more "aggressive" than this case, alveolar and embryonal have more "embryonal" "small blue round cells" than here, no alveolar pattern, and not sclerosing type also, in addition to desmin negativity.
When you review the list of spindle cell soft tissue tumours (may be accompanied by rhabdoid features) and correlate with age and site, together with that defective pannel performed, synovial sarcoma is the most suitable diagnosis!!

I strongly suggest the possibility of Rhabdomyosarcoma

S100 negativity excludes melanoma. I don't understand why this case was diagnosed as synovial sarcom ?. Please give me an explanation.

Cytology wise, this case showed highly cellular smear featuring single cells with cytoplasmic tailing, eccentric nuclei, and prominent nucleoli. Some cells showed glassy red cytoplasm and binucleation in tissue sections. These features are in favour of melanoma. The history mentioned and presence of neutrophils are against nodular faciitis. I have no experience with synovial sarcoma with eccentric nuclei and glassy cytoplasm. The characteristic geographic necrosis which favours epithelioid sarcoma is not appreciated in images. I suggest melanoma as a strong possiblity.

calponin and CD56 in 26.6%; CD99, CK AE1-AE3, CK19, CK7, and EMA in 80%; and S100 negative in all.

Thanks for the good case!

Excellent, it was diagnosed as monophasic synovial sarcoma: slightly pleomorphic but malignant cells (unlike nodular fasciitis) clearly observed in touch preparation, high nuclear to cytoplasmic ratio, with scant, delicate, tapering cytoplasm, rhabdoid features are accepted in synovial sarcoma, The nuclei of a leiomyosarcoma have blunted or truncated
(rather than rounded) ends, and cytoplasm is
denser. Some nuclei of an MPNST are more curved and pointed, and there is greater nuclear pleomorphism. A solitary fibrous tumor has fewer dispersed cells and more complex cellular clusters, with ropy collagen fibers and blood in the background.
EMA and CK were a must.
Please Dr. Qiao, why do you recommend bcl2 and calponin??

Additional IHC stains will be: EMA, bcl-2, and calponin .

No, it isn't PNET at all, revise what soft tissue tumour is CD99 +ve in about 70% of cases and consider age and site!!
and what immune stain do you recommend for further confirmation?? (Unfortunately it wasn't done)

but the cells are larger with abundant cytoplasm.

Thank you all for your precious comments.
SMA, S100 and desmin were all negative, and guess what was positive ??
CD99 was focally positive.
what do you think??

Vimentin,, EMA,smooth muscle actin and CD34are recommended to confirm epithelioid sarcoma although nod.fasciitis could be positive for actin

the long duration, recurrency and location in addition to the histologic picture give rise to the diagnosis of nodular fasciitis....awaiting for immuno!

?? Proliferative Fascitis

It is really a difficult case my ddx is broad in this case including solatory fibroma, although can not rule out fibrosarcoma (mitosis) is not frequent. is it?, PNET although ressettes are not present : ) Ganglioma..........
looking forward for the final answer

Low power view of the smears looks like tissue-culture appearance...

Excellent point, it is indeed the first possibility, but epithelioid sarcomas typically grow as nodular, vaguely circumscribed, infiltrative masses, often with central necrosis with bland nuclear features. Let us postpone IHC results and discuss more differential diagnoses.

Epithelioid sarcoma most frequently affects hands and forearms followed by distal lower extremities and proximal upper extremities.

Epithelioid sarcoma is the most common soft-tissue sarcoma in the hand and most commonly occurs in young adults.

Nice case and nice photos ! Any IHC stains?