title: "A 40-year-old female with painless, slow growing prepatellar mass".
abstract: A 40-year-old woman from India presented with a mass in the front of her left knee which had been present for 8 months. Local examination revealed a globular mass of approximate size 5 cm × 4 cm × 4 cm in front of the lower pole of left patella. The patient was investigated with imaging studies and laboratory tests. Plain radiograph of the chest was normal. In addition, contrast enhanced Magnetic Resonance Imaging (MRI) of the left knee was performed. Based on the history, physical examination, laboratory and imaging studies, what is the differential diagnosis?
authors.affiliation: Department of Orthopaedic Surgery, The Maulana Azad Medical College & Associated Lok Nayak Hospital, New Delhi 110002, India.
authors.forename: Sumit
authors.initials: S
authors.lastname: Arora
authors.affiliation: Department of Orthopaedics/ Spine Surgery, Indian Spinal Injury Center, Vasant Kunj, New Delhi 110070, India.
authors.forename: Sahil
authors.initials: S
authors.lastname: Batra
authors.affiliation: Department of Pathology, Sir Ganga Ram Hospital, New Delhi 110060, India.
authors.forename: Seema
authors.initials: S
authors.lastname: Rao
authors.affiliation: Department of Orthopaedic Surgery, The Maulana Azad Medical College & Associated Lok Nayak Hospital, New Delhi 110002, India.
authors.forename: Lalit
authors.initials: L
authors.lastname: Maini
authors.affiliation: Department of Orthopaedic Surgery, The Maulana Azad Medical College & Associated Lok Nayak Hospital, New Delhi 110002, India.
authors.forename: V K
authors.initials: VK
authors.lastname: Gautam
keywords: Excisional biopsy; Prepatellar mass; Synovial sarcoma