Convert a POI RichTextString to HTML or RTF

I have an application where I am reading in an Excel file using Apache POI. Some of the cells may have formatting (bullets, underline etc). What I want to do is then display the contents of the Cell in a HTML page - keeping the format.

I have seen answers that can convert RTF strings to HTML - so that I can do.

I can see a lot of answers going from RTF to POI RichTextString - but I want to go the other way - i.e., convert the value stored in the Cell represented by RichTextString into an actual RTF string (or HTML).

Has anyone done this?