Forehead soft tissue nodule not lipoma? (Photo)

In this case, I would get an MRI to confirm the presence or not of a lipoma. Their signature on MRI is pretty diagnostic.  Once confirmed, re-operation would be reasonable.  You might then have your original or another board-certified plastic surgeon re-operate. For reasons other surgeons have listed, the lipoma might have been missed during the first operation.

Sorry you are having this problem. Quite correctly, your physician sent you for a CT evaluation prior to any surgical intervention. CTs and ultrasounds are typically pretty good in making sure that the lump does not relate to underlying bone or nerve problems. If scar tissue is playing a role in the bump, the injection of an anti-inflammatory agent may help to shrink it and make it much less visible, used either alone or in combination with a small amount of hyaluronidase. If a deeply located lipoma is the culprit, Kybella, rather than repeat surgery, may be considered to inject it and shrink it (although this is a completely off-label use of this product, which is approved for treating submental--double chin--fat deposits). At this point, you might consider seeking a second opinion. Best of luck. 

Thank you for sharing your question and photograph and I am sorry to hear of your soft tissue mass that has persisted for 10 years.  In most instances a CT scan or ultrasound should provide the appropriate diagnosis as the tissues are thin enough to allow excellent resolution. Though nothing replaces an in-person examination I would seek a second opinion as a lipoma looks likely.  Hope this helps.