Review Question - QID 109739

A 29-year-old African American man presents to his primary care provider complaining of right knee pain. He reports a 3 month history of slowly progressive dull pain on the proximal aspect of his right knee and proximal leg. His past medical history is notable for gout and obesity. He takes allopurinol. His family history is notable for gout and rheumatoid arthritis in his father. His temperature is 99.3°F (37.4°C), blood pressure is 115/75 mmHg, pulse is 80/min, and respirations are 16/min. On exam, he demonstrates 5/5 strength throughout his left lower extremity. There is mild tenderness to palpation over the tibial tuberosity. Sensation to light touch is intact in the saphenous, sural, deep peroneal, superficial peroneal, and tibial distributions. Patellar reflexes are 2+ bilaterally. A radiograph of the patient’s right leg is shown in Figure A. Which of the following cell types is proliferating in this patient’s lesion?