Hi and welcome to the community, though sorry to hear about how you came here.
As you probably know already sarcomas are a fairly rare form of cancer and it would appear hystiocytic sarcoma is rare even among these, I did not find any other references in the community area and even general web searches do not seem to provide much in the way of data.
I wish I had a better answer for you because I know when my wife was diagnosed with Leiomyosarcoma I felt quite grateful to find the handful of other patients with the same diagnosis but even then our path through cancer can be quite different.
<<hugs>>
Steve
