PMC6323454_01
Preoperative MRI. Axial T1 MRI (a), axial STIR MRI (b), and sagittal STIR MRI (c) revealed the prefemoral fat pad (white arrowhead). The fat pad was located superolaterally to the PF joint, and hyperplasia was confirmed. There were no fibrous septa or mild peripheral enhancement patterns that were suggestive of lipoma.
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Both T1- and T2-weighted images at high signal intensities revealed the soft tissue mass, while low signal intensity was noted under fat suppression and no contrast enhancement was noted under contrast imaging (Figure 1).
Intraoperative arthroscopic view. (a, b) Arthroscopic view of the anterolateral portal before excision of the prefemoral fat pad. The fat pad resembled normal adipose tissue, and there were no characteristics of lipoma such as round/oval masses, fibrous capsules, or vascular pedicles. Mild laxity was observed. (c) A piece-by-piece excision of the prefemoral fat pad was performed.
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There were no other intra-articular findings, and a piece-by-piece resection was eventually performed (Figure 2).
Histological findings consisted of connective tissues that were mainly composed of fat, and synovial covering was not inflamed. There were no fibrous capsules, vascular pedicles, or villous projections that were suggestive of lipoma, lipoma arborescens, or pigmented villonodular synovitis (hematoxylin and eosin (HE); magnification: (a) x40, (b) x100).
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Histologically, the mass consisted of connective tissue that was mainly composed of fatty tissue, and there were no findings that suggested the presence of lipoma, lipoma arborescens, or pigmented villonodular synovitis (Figure 3).
10-month postoperative axial STIR MRI. The fat pad was completely removed and no recurrences were found.
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There was no evidence of the preoperatively confirmed fatty mass in postoperative MRI imaging, and no recurring lesions were found (Figure 4).