Hello
thanks for your query.
The condition you have is called endometrial hyperplasia.
There are different types of endometrial hyperplasia , and they are sorted out on the basis of the biopsy results.
The risk of progression to uterine cancer depends on the type found on biopsy.
ANd even then, the risk in certain types of hyperplasia is also less than 5 %.
For the remaining types, the risk is next to nil.
So please dont worry, and yes, with the thickening of the lining to 21 mm, it is better to go for biopsy straightaway.
Take care.

Thank you for your question. Your doctor is giving you sage advice. The missing piece of the history in this case is your age and whether or not abnormal bleeding is occurring. Fibroids are present in up to 70% of women. Given that statistic, it is probably normal to have fibroids. Problems arise when fibroids cause symptoms such as abnormal bleeding, pain, cramps or trouble conceiving. It is rare for a fibroid to become cancerous but that can also occur.
Ultrasound has given you and your doctor the size of the fibroids and the measurement of the lining of the uterus, which is thickened. A biopsy of that lining is indicated to make sure there is nothing worse (like cancer) that is making the lining thicker than it should be. A saline infusion ultrasound is done to introduce fluid into the uterine cavity. This can help determine the presence of polyps and can help decide if one of the fibroids is protruding into the cavity, both of which can show thickened lining on a regular ultrasound.
Both of these procedures can be done in the office and involve traversing the cervix which may cause cramping. Premedication is often helpful to reduce anxiety and decrease discomfort. Both procedures will help you and your doctor decide if any further treatment for the fibroids is warranted.
I hope this answers your questions. I am available for further consultation or questions.