Nodular fasciitis with intra-articular presentation within the knee

Area of Science:

• Orthopedic Surgery
• Pathology
• Oncology

Background:

• Intra-articular masses in the knee can present diagnostic challenges.
• Nodular fasciitis (NF) is a rare benign soft tissue tumor.
• Distinguishing NF from other intra-articular tumors is crucial for appropriate management.

Purpose of the Study:

• To report a rare case of intra-articular nodular fasciitis (NF) in the knee.
• To highlight the diagnostic challenges and importance of specific biomarkers.
• To emphasize the successful outcome following surgical excision.

Main Methods:

• Case presentation of a female patient with atraumatic knee pain.
• Imaging studies including MRI to characterize the retropatellar mass.
• Open surgical excision and histopathological analysis, including USP6 staining.

Main Results:

• Imaging revealed a heterogeneous, contrast-enhancing mass in the retropatellar fat pad.
• Histopathology confirmed intra-articular nodular fasciitis (NF).
• Detection of ubiquitin-specific protease 6 (USP6) was key to diagnosis.

Conclusions:

• Intra-articular NF is a rare entity that can mimic other intra-articular tumors.
• USP6 detection is crucial for accurate diagnosis of NF.
• Surgical excision resulted in improved knee function and return to work.