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Gout is a disease where an abnormal collection of uric crystals (gouty tophi) can often be found in the foot and ankle. Occasionally such tophies are found at unusual sites and this can pose a challenge to the clinician where diagnosis and treatment is concerned. We describe a patient who presented to our oncology department with a swelling on his right thigh which was clinically diagnosed to be a soft tissue sarcoma, but after further investigations it turned out to be a gouty tophi. The purpose of this case report is to emphasise the variable presentation of gout and the challenges that can be faced by clinicians in diagnosing a soft tissue swelling.
Gout has been known as a “great mimicker” since ancient Greek times when Hippocrates attempted to differentiate it from rheumatoid arthritis.1 It has been reported to mimic joint2 and soft tissue infections,3 skin malignancies, nerve compression syndromes4 and soft tissue tumours. Gouty tophi are often found in the foot around the big toe as well as the ankle region. Although there have been reports in the literature on gouty tophi appearing in numerous other tendons in the body, a routine search found no report of tophi occurring in the quadriceps tendon alone, except in a report of an unusual cause of quadriceps atrophy.5
What made this case interesting was that it was initially referred to our oncology department as a soft tissue sarcoma, and all the initial imaging studies were suggestive of a malignant soft tissue tumour. This begs the question: can gout mimic a tumour?
A 50-year-old man was referred to our orthopaedic oncology department with pain and swelling over his right thigh for the duration of 4 months. The pain started insidiously 2 years previously. There was no history of preceding trauma. The pain progressively worsened over the last 4 months. It was aggravated when he tried to straighten his knee and when he walked. It became so severe that he could not straighten his knee when he presented to the clinic. He was only able to walk for more than 10 m due to the pain.
Associated with the pain, he noticed a swelling over the anterolateral aspect of his thigh just above the patella (fig 1), which was progressively getting larger over the last 4 months. There was no history of fever, loss of appetite, or loss of weight.
Physical examination revealed a firm swelling at the anterolateral aspect of his right thigh, above the patella, measuring 8 cm × 10 cm. The swelling was attached to the quadriceps tendon. There were no skin changes nor were there signs of inflammation. The range of movement of his right knee was 40–90°, limited mechanically by the swelling.
Laboratory findings showed a normal full blood picture. The patient’s erythrocyte sedimentation rate (ESR) was 1 mm/h, the total white count was 7900/mm3, but uric acid values were elevated (9.0 mg/dl). Plain radiograph of the right knee showed a soft tissue shadow over the right patella at the region of the quadriceps tendon (fig 2). T1 weighted magnetic resonance imaging showed a heterogenous mass arising from the quadriceps tendon with involvement of the periosteum of the femur (fig 3). An ultrasound guided biopsy was performed. It was noted that the biopsy yielded chalky white material. To our surprise the biopsy showed gouty tophi—needle shaped, doubly refractile crystals with negative birefringence and granulomatous response.
A wide excision was performed and a well encapsulated mass measuring 8 cm × 10 cm was seen arising within the tendon of the quadriceps muscle (fig 4). Dissection of the mass revealed white, chalky deposits within it (fig 5).
The histopathology report of the resected specimen showed collagenous tissue with a large area of light eosinophillic fibrillary deposits surrounded by foreign body-type giant cell reaction. The deposit were non-birefringent (fig 6). Postoperatively, the wound recovered well; the patient regained some of the knee motion and the mechanical pain reduced to a functional level. At 6 months follow-up, his range of motion improved (10° to 100°) and the patient is still under our follow-up.
Gout is a condition that results from an overload of uric acid crystals that deposit in tissues of the body and features recurring attacks of acute joint inflammation. Chronic gout can lead to deposits of hard lumps of uric acid in and around the joints and tendons. Gout has been known to mimic such diverse conditions as joint and soft tissue infections, nerve compression, and even soft tissue tumours.
Gouty tophi have been reported to mimic cancerous conditions in other part of the body such as the synovium,6 the hand,7 and the forearm and foot.8 Gouty tophi had even been reported to mimic squamous cell carcinoma.9
This case illustrates the variable presentation of gout. The diagnosis of any soft tissue swelling such as gout is not always easy, especially if it occurs in an unusual place. Furthermore, not all gouty trophy presents with the typical presentation of joint pain in the foot. A high index of suspicion and a simple test such as an ultrasound guided biopsy can help to distinguish these cases from the more sinister ones and avoid the need for more elaborate and expensive tests. Symptomatic gouty tophi are best treated by surgical resection.
Competing interests: None.
Patient consent: Patient/guardian consent was obtained for publication.