A 25-year-old male presents to the clinic with a painful, enlarging mass at the volar radial wrist. He initially noticed the mass 6 months ago after he hurt his wrist golfing. Figure A shows a clinical photograph of the patient's wrist. Radiographs are unremarkable. An ultrasound of the mass is shown in Figure B. Surgical excision is planned. Which of the following is the most appropriate type of resection and histologic finding?