Large Bump After Lipoma Surgery- What Could This Be?

By your description, the bump may be a fluid collection of either blood(hematoma) or a seroma ( fluid created by the body in response to an injury). However, the person to best answer your question is the physician who performed the surgery. If you do not feel that you are receiving enough information from your surgeon, you could ask if a second opinion would help to alleviate concern.

My concern in the initial postop period would be formation of a seroma, or fluid collection, or a hematoma. Please return to your plastic surgeon for follow up and, if you are unhappy with the response, seek a second opinion. It is far too early to have regrowth of the lipoma.

A mass like after removal of lipoma, think seroma, hematoma, most logical if the lipoma was removed .

Lipoma is a clump of 'organized'  dividing adipocytes.

It is not unusual for Lipoma to return at the original site, but it has to take months in order to do so. 9 days post-operatively is too early for fat cells to re-group.

Rapid swelling at the surgical site if there is no infection might indicate development of seroma - inflammatory fluid collection between tissue planes. It is seen following surgery in response to injury of the operative intervention.

Ask your doctor to do an Ultrasound scan to establish the reason for that rapid swelling.

Simple aspiration and subsequent compression is all what is needed if this diagnosis is proven.