Clinical diagnosis
Case 267
【Discussion】
Synovial chondromatoisis arises from chondroid metaplasia producing multiple cartilage body that grows into joint space and some detach from synovial capsule, inducing loose body. Cartilage bodies are produced not just from joint capsule but also bursae and tendon sheath, leading many cartilage bodies or nodules in the joint spaces (1- 3). The produced cartilages are shown high signal intensity on T2WI and low signal intensity on T1WI, indicative of cartilage containing high content of water (1). Further, calcification is becoming to be included in the center or rim of high-water content cartilage, called stippled calc or ring and arc calc (4). Synovial chondromatosis is categorized into primary and secondary; primary chondromatosis is usually comes from one major joint, knee joint most, followed by hip joint and shoulder joint: secondary chondromatosis comes from mechanical or traumatic arthritic damages, indicating it emerges from bilateral joints or injured joint (1-3). Specific calcification in swollen joint space is shown on radiographs and CT. Relatively massive cartilage with high content of water is depicted low attenuation mass on CT and high signal intensity on T2WI & low or intermediate signal intensity on T2WI. Calcification in cartilage body with high-water- component is depicted on CT and it is shown low signal intensity irrespective of on T1WI or T2WI.
For differential diagnosis, pigmented villo-nodular synovitis (PVNS), amyloid arthritis, gout and rheumatoid arthritis are listed. Synovial membrane composes of fibroblast-like cells that produce hyaluronic acid, mucin protein, macrophage-like cells that clear foreign body and fenestrated capillaries that supply nutrients to synovial membrane (5 - 7). PVNS produces brown-colored villi and nodules. Brown-colored implies hemosiderin deposit oozing from fenestrated capillaries. Villi and nodules come from proliferation of fibroblast-like cells (5 - 7). Although hemosiderin and calcification are shown low signal intensity on T2*WI, the differentiating point between PVNS and synovial chondromatosis is whether cartilage with high content of water is present or not, that is depicted high signal intensity on T2WI and low signal intensity on T1WI.
Amyloid arthropathy is rare but it often encounters in chronic renal insufficiency with renal hemodialysis. Amyloid is unable to be filtered by renal hemodialysis. Then, amyloid accumulate in case of long-term hemodialysis. On joint rea, it accumulates at subchondral area causing pathological fracture like bone metastasis.
In our case, swollen right knee is occupied by massive lesion with low signal intensity on T1WI and high signal intensity on T2WI mimicking massive intraarticular fluid. This lesion includes small many nodules with low signal intensity on both T1WI and T2*WI indicative of calcification, although it is difficult to differentiate between hemosiderin and calcification on MRI alone.
【Summary】
We presented a seventy four-year-old male suffering from right knee pain for the past four months. Massive lesion mimicking joint fluids occupied the right knee joint with high signal intensity on T2WI and low signal intensity on T1WI. It contains small nodules with ring and arc formed low signal intensity on both T1WI and T2WI, indicative of calcification from cartilage. It is borne in mind that synovial chondromatosis arises from chondroid metaplasia producing atypical chondroid matrix that composed of higher water cartilage rather than normal cartilage. It is shown high signal intensity on T2WI and low signal intensity on T1WI mimicking joint fluids. Further, it contains calcification with configuration of ring and arc indicative of arising from cartilage.
【References】
1.Murphey MD, Walker EA, Wilson AJ et-al. From the archives of the AFIP: imaging of primary chondrosarcoma: radiologic-pathologic correlation. Radiographics. 23 (5): 1245-78.
2.Coles MJ, Tara HH (January 1997). "Synovial chondromatosis: a case study and brief review". Am. J. Orthop. 26 (1): 37–40.
3.Crotty JM, Monu JU, Pope TL (March 1996). "Synovial osteochondromatosis". Radiol. Clin. North Am. 34 (2): 327–42, xi. PMID 8633119.
4.FletcherCDM, UnniKK, MertensF, editors. Pathology and genetics of tumours of soft tissue and bone. World Health Organization classification of tumours. Lyon: IARC Press, 2002
5.Mark K, et al. Pigmented Villonodular Synovitis: Radiologic-Pathologic Correlation. RadioGraphics. 2008; 28(5):1493-51
6.Barile A, et al Pigmented villonodular synovitis (PVNS) of the knee joint: magnetic resonance imaging (MRI) using standard and dynamic paramagnetic contrast media. Report of 52 cases surgically and histologically controlled. Radiol Med. 2004 Apr;107(4):356-66
7.Bravo S, et al. Pigmented Villonodular Synovitis. Radiol Clin North Am. 1996;34(2):311-26.
2022.5.31