John Becker Ronald J. Boucher Ronald Chan Lisa Corrente Keir Fowler John Hopkins Kristina Kjeldsberg Emily Lee Robert Lee Kay Lozano Nataliya Plyushcheva Herman Wu Maritza Angulo Ilma Isaza Tony Stanley Grant Brunet Edmund Tsui

Kristina Kjeldsberg 62 yo active female with slowly growing mass at the plantar aspect of the right foot with discomfort.

T1 STIR T1+C 62 yo active female with slowly growing mass at the plantar aspect of the right foot with discomfort.

T1 T1+C Incidental TC coalition 62 yo active female with slowly growing mass at the plantar aspect of the right foot with discomfort.

Findings 2.0x1.3x1.3 cm T2 hyperintense, avidly enhancing, well-circumscribed mass at the plantar aspect of the foot, deep to the flexor tendons between the 2 nd and 3 rd MT. Appearance most consistent with a benign nerve sheath tumor. Synovial sarcoma also should be considered, however, this usually has more infiltrative margins and would be unusual in this patient’s age group.

Pathology Benign encapsulated nerve sheath tumor, most consistent with a schwannoma.

Discussion-benign peripheral nerve sheath tumor Schwannoma and neurofibroma. Circumscribed fusiform mass. May see entering/exiting nerve. Isointense to muscle on T1. Hyperintense on T2. Can have central low signal intensity (“target sign”) due to collagen and condensed schwann cells. Variable enhancement. “split fat sign”- peripheral rim of fat Malignant degeneration very rare in schwannomas and solitary neurofibromas. 4% in NF-1.

Kristina Kjeldsberg 43 yo female with chronic progressive right ankle pain and swelling.

Findings Lobulated low signal intensity masses are seen extensively throughout the tibiotalar, distal tibiofibular, and subtalar joints with associated prominent osseous erosions at both sides of the joints. Findings consistent with extensive pigmented villonodular synovitis.

Operative Report Extensive PVNS Treatment: anterior, posterior, and subtalar synovectomies and bone grafting of the defects in the talus and tibia.

Discussion-PVNS Locally destructive fibrohistiocytic proliferation and villonodular protrusions of synovial membranes affecting joints, bursa, and tendon sheaths. Lobulated masses with low signal intensity on all pulse sequences. Subchondral erosions. Usually monoarticular (knee 80%). Presents with joint swelling and insidious onset of pain. Decreased range of motion.

Herman Wu 43 year old male with lateral right ankle pain chronically.

Accessory ankle muscle and tendon

Herman Wu 9 year old male with left hip pain

Legg-Calve-Perthes Case 1: Legg-Calve-Perthes; question regarding expected amount of associated bone marrow edema and synovitis.

Herman Wu 33 year old female with knee re-injury H/o ACL repair

33 year old female with knee re-injury H/o ACL repair

Fabellar dislocation Case 2: fabellar dislocation on MR; question regarding lack of gastrocnemius injury

Herman Wu 13 year old female with left knee pain Contralateral knee MRI several months before showed normal marrow signal

13 year old female with left knee pain

Case 3: Ollier's disease vs hemangioma/lymphangioma of bone?

Herman Wu 41 year old male with foot pain and no history of trauma

Mueller-Weiss Case 4: Mueller-Weiss

Herman Wu 69 year old male with left arm pain

Case 5: BPOP/Nora lesion vs intracortical chondroma?