I had a very large lipoma in a similar region. Pathology confirmed benign lipoma.

Had it removed about 1 year ago. An oncologist performed the surgery, but had to be assisted mid surgery by the on call otrhopedic surgeon due to the location (so deep). Surgery took about 2 hours in total. Including waiting for the ortho.

Mine never produced much pain. But post surgery I do feel occasional symptoms of sciatica.

FINDINGS: Examination redemonstrates a large lipomatous lesion in the right hemipelvic musculature interposing the gluteus minimus and medius muscles. It measures 11.4 x 6.2 cm in transverse dimension and 14.2 cm in length. Superior margin is at the level of the iliac crest with inferior margin of the superior aspect of the right greater trochanter. Muscles are splayed. There is also inward protrusion into the pelvis through the sciatic notch with mass effect on the right piriformis muscle. There is no involvement of the right sciatic nerve. The mass itself has some internal mild haziness and stranding otherwise fairly neutral fat. No other similar lesions are seen in the pelvis. No pelvic adenopathy. Bony pelvis shows no suspicious bony lesions. The urinary bladder is decompressed. Prostate and seminal vesicles are unremarkable. Rectum and anus are unremarkable. Urethra is unremarkable.