I too had a fibromyxoid sarcoma removed 12 years ago. It was also in my leg behind my left knee. I also had it resected, and received very aggressive chemo, and radiation therapy. My oncologist told me if there is metastasis, it will go to the lung. He never mentioned the thyroid to me. He also said if metastasis were to occur it would be within 5 years. After the 5 year mark you have a 95 % chance of beating it. Hope this helps and good luck.
I have a rather chequered history in respect of my fibromyoxid sarcomas. My first tumour was in my right shoulder and was excised in 1979 aged 19. It took nearly 20 years to reoccur (1998) in exactly the same place despite wide margins, this too was excised without chemo or radiotherapy. However during my regular 6 monthly f/ups they discovered that it had metastasized into my lungs. I had the lung met (1) surgically removed in 2006. Only to find that a month later they found another two small mets in my lungs. 'Wait and watch' was the preferred approach. F/up revealled no growth until recently when St James Oncology centre ( reputed to be the best in Europe) contacted me stating that they had detected suspected changes. This is 5 years post op. Suppose I am just under the 95% odds. That said I have read that radiotherapy is now being used in Japan to erradicate LGFS lung mets with good results. I suppose we are lucky that these 'little or big blighters' grow slowly and are not that aggressive. I am interested to understand why Darlacan's Mum's lung mets are inoperable? Additionally I wonder why so many people are not treated with adjuntive therapy thereafter?
I dont wish to distress or upset anyone else with my tale or for them to lose hope. Everyone is different. Good luck to you both.