Intrauterine Injection of Type III Collage in FST of EC/AEH

The goal of this clinical trial is to learn if intrauterine injection of "Recombinant Humanized Type III Collagen Lyophilized Fibers" works to treat endometrial cancer or atypical hyperplasia in patients seeking fertility-preserving treatment. It will also learn about the safety of this intervention.The main questions it aims to answer are:

1. Does the combination of recombinant humanized type III collagen and progestin significantly increase the tumor remission rate at 6 months compared to progestin alone? 2. What medical problems do participants have when receiving this treatment (e.g., allergic reactions, abnormal inflammatory markers, or histocompatibility issues)? Researchers will compare "recombinant humanized type III collagen plus progestin (experimental group)" to "high-dose progestin alone (control group)" to see if the combination therapy is more effective for fertility preservation.

Participants will:

1. Take high-dose progestin (such as Medroxyprogesterone Acetate or Megestrol Acetate) orally every day. 2. If assigned to the experimental group, receive one intrauterine submucosal injection of collagen via hysteroscopy at months 0, 1, and 2, for a total of 3 injections. 3. Visit the clinic once every 3 months for treatment evaluation and follow-up, which includes hysteroscopic endometrial biopsy, imaging (such as transvaginal ultrasound), and safety tests for relevant biochemical indicators.