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Abstract
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Purpose
We present a case of an intra-articular nodular fasciitis (NF) of the hip, which is a rare benign lesion usually arising from subcutaneous, fascial or subfascial sites of the upper extremities, followed by the head and neck, trunk and lower extremities. To our knowledge, there is only one other report in the literature of an intra-articular occurrence in the hip.
Case
A 50-year-old man complained of groin pain on the right side for 3 months. The clinical examination of the hip revealed a positive anterior impingement sign and a moderate tenderness on palpation in the groin. The MRI of the hip showed an extensive synovialitis and joint effusion and an increased alpha angle 64° (norm < 50°) as a correlate for a Cam impingement. A diagnostic and therapeutic arthroscopy was performed for biopsy, complete synovectomy and offset correction. The histological result revealed an unspecific aspect with mucoid changes comparable to ganglion cysts, no sign of malignancy. 4 month after the arthroscopy the symptoms still remained. The new MRI showed a significant growth of the intra-articular tumor around the neck of the hip. To obtain a new histology, a CT aided biopsy was performed. As a NF kept in mind, molecular-genetic next generation sequencing detected a MYH9-USP6-gen-fusion.
Discussion
Most cases in the literature describe a joint involvement of the knee. The symptoms vary from pain in the affected joint to joint effusion, painful mass, catching sensation and limited range of motion. The MRI usually identifies a lesion with an iso- to hypointense signal in T1- and a hyperintense signal in T2-weighted sequences. Histologically, it is defined as a benign proliferation of fibroblasts and myofibroblasts, abundant spindle-shaped cells, which are arranged within a variably loose myxoid to collagenous stroma. Immunohistochemically, the spindle cells are positive for alpha-smooth muscle actin (SMA). The identification of a MYH9-USP6 gene fusion by RT-PCR is de-scribed as a useful tool to corroborate the diagnosis. The therapy consists of arthroscopic resection with good result. The published case reports showed no recurrence after resection, in our case we observed a re-growing mass after about 4 months. After 1 year we haven’t performed a reoperation with a sub symptomatic patient.
Conclusion
We describe a rare intra-articular NF of the hip, which, in contrast to the published cases, presented with a recurrence after arthroscopical resection.
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