Background:

Pseudotumor of the tensor fascia lata (TFL) consists of a rare, benign soft tissue mass/hypertrophy of the TFL that appears on the anterolateral aspect of the proximal thigh. Notably, this condition often mimics a malignant tumor and may be misdiagnosed as a sarcoma.

Case description:

A 45-year-old male presented with left hip/groin pain, swelling, and a painful mass on the anterolateral aspect of the left hip/thigh. The symptoms had started 3 months ago following an L1-S1 lumbar laminectomy/fusion. The initial diagnosis was hip disease, and the patient underwent a left MR arthrogram. When this study demonstrated a tear of the left anterosuperior acetabular labrum plus an increased alpha angle causing femoroacetabular impingement, the patient then underwent a left hip arthroscopy. However, as he continued to complain of the hip mass, he was referred to an orthopedic oncologist whose presumptive diagnosis favored a sarcoma. Nevertheless, the pelvic MRI scan and ultrasound (US) confirmed the diagnosis of hypertrophy of the left TFL (US left 33.4 mm vs. right 14.4 mm). The patient was first treated with 50 units of locally injected botulinum. As there was no symptomatic relief, the plan was to repeat the injection within the next few months.

Conclusion:

Hypertrophy of TFL may mimic a neoplasm such as a sarcoma and contributes to what appears to be a lumbar radiculopathy. However, MR and US imaging should readily identify TFL and rule out malignant lesions such as sarcomas.