Leiomyosarcomas are well known for local recurrence and metastatic spread.  The metastases are usually [95% or more] spread through the bloodstream, but there are cases of lymphatic spread.

Early surgical removal of the tumor, before it spreads elsewhere, and with wide clear margins, so it is less likely to recur in the same place, is the best thing to have done, and this MIGHT accomplish a cure.  

Tumor invasion of lymph channels or blood vessels, or of other organs, larger size of tumor, necrotic areas with hemorrhage, many mitoses...all are poorer outcome signs, because of the likelihood that the tumor is more aggressive and has already metastasized.

Because of the "returning" nature of the LMS, it is still necessary to have close supervision by a cancer doctor every three months. If metastasis or local recurrence occurs, it can be dealt with.  Surgical intervention is generally considered best if it is possible, unless the tumor is CD117 positive and the designer drug, the chemostasis agent STI-571 [Glivec] can be used.  Then you may have choices.