A 57-year-old male patient was admitted to our hand surgery department complaining of a progressive swelling located on the dorsoulnar side of the right wrist joint. The patient reported that the mass was started to grow for the past three months. On physical examination, there was no tenderness or erythema around the mass. The range of motion of the wrist joint was within the normal range. Neurovascular examination findings were normal. The patient was not diagnosed with any chronic disease previously, including gout or not under any medication. He had a history of an occupational injury 33 years ago in which he lost extensor muscles and tendons on the right forearm. Thus, the patient underwent a tendon transfer surgery in which the FCU tendon was transferred to EDC tendon (Figure 1). The patient's family history was unremarkable for gout. 
Magnetic resonance imaging (MRI) revealed an iso/hypointense mass at proton density-weighted and fat-suppressed T1 images (Figure 2). We decided to perform excisional biopsy. A written informed consent was obtained from the patient. During surgery, it was confirmed that the FCU tendon was transferred to EDC tendon. The tumor was located within the junction where the FCU tendon was transferred to EDC tendon. Non-absorbable suture materials were observed within the tendon transferred region (Figure 3). A caseous material was reached following the opening of the paratenon suggestive of tendon necrosis, tuberculosis, or a foreign body reaction. An excisional biopsy was performed, and the specimens were sent for histopathological and microbiological evaluation. The weakened tendon was repaired with eight-strand and epitendinous sutures. 
No organism was seen in the initial Gram staining, and there was no bacterial growth in the microbiology cultures. His preoperative blood laboratory test results were within normal ranges for complete blood count, complete metabolic panel, and uric acid levels. Microscopic examination revealed typical morphology of a gouty tophus. A granulomatous inflammation consisted of a fluffy cotton candy-like material and surrounding foreign body giant cells. At the periphery, fibrotic synovium was visible (Figure 4). Since urate crystals are dissolved in formalin fixation, microscopic examination under polarized microscope failed to demonstrate urate crystals. The patient was consulted with rheumatology department and antigout therapy was initiated. The patient's wound was healed without any complication. There was no recurrence at 18 months of follow-up.