Right off the top of my head, I can't think of anyone who has dealt with Lymphangioma in that location. I can think of two parents who had children with lymphangioma in the neck.
I'll ask around, though.
Also, hi and welcome!
If sclerotherapy is the suggested treatment and might lead to another surgery anyway, will you push for surgery rather than sclerotherapy? I'm curious to know why you didn't return to the orthopeidc surgeon this time as well (just curious, not questioning your decision!!).