Clinical diagnosis
Case 258
【Discussion】
Auricular joint is covered with synovial membrane which composes of macrophage-like cells and fibroblast-like cells. Macrophage-like cells phagocytes foreign body inducing auricular fluid clean and fibroblast-like cells secrete hyaluronic acid and mucin protein, inducing to avoid friction between cartilages. Synovial membrane does not own basement membrane but fenestrated capillaries which supply nutrients to synovial membrane and cartilage (1-3).
PVS figures such as cauliflower, broccoli or frond. It composes of brown-colored villi and nodules macroscopically. Microscopic findings of PVS show proliferation of fibrous stroma and cells proliferation with hemosiderin deposit: mononuclear round cells probably arisen from fibroblast-like cells creating fibrous stroma, and multinucleated giant cells probably arisen from macrophage-like cells.
Although the term of pigmented villo-nodular synovitis (PVNS) seems to be inflammation, it is now thought to have neoplastic character because it gradually grows and recurs after surgical treatment (4).
Synovial membrane exists in not only auricular joint but also bursa and tendon sheath. Then, the similar lesion occurs: when it occurs in auricular joint, it is termed pigmented villo-nodular synovitis (PVNS), when it occurs bursa and tendon, they are termed pigmented villo-nodular bursitis (PVNB) and pigmented villo-nodular tenosynovitis (PVNTS); PVNS occurs in knee most, approximately 75%; PVNTS occurs in finger or wrist: PVNB occurs in knee and hip (4). PVNTS is often termed giant cell tumor of the tendon sheath. Giant cell tumor implies proliferation of macrophage-like cells. PVNS is largely classified into nodular type and diffuse type. PVNB and PVNTS emerge as nodular type.
MRI is diagnostic for diagnosis of PVNS, PVNB or PVNTS, irrespective of diffuse or nodular (4 - &). They include proliferation of macrophage-like cells which phagocyte foreign body, namely, hemosiderin bleeding from fenestrated capillaries, indicating hemosiderin deposit in cells or stroma. Further, fibroblast-like cells form fibrous stoma like frond or broccoli. Gradient echo T2*WI MRI is quite sensitive to bleeding detection and depict hemosiderin as low signal intensity. Findings of PVNS is called blooming artifact since much hemosiderin causes strong distortion of magnetic field (4-6).
In our case, T2*WIMRI depict marked low signal intensity along with articular capsule, indicating hemosiderin deposit. Blooming artifact which is characteristic of PVNS is also demonstrated on T2*WIMRI (Figs. 1-3).
The annual estimated incidence of pigmented villo-nodular synovitis (PVS) is 9.2 per one million (one per one hundred thousands) that indicate one per each other year in the population of fifty thousands of Hannan city.
【Summary】
We presented an eighty one-year-old female for swollen and painful right knee. A local clinic orthopedist suspect pigmented villo-nodular synovitis (PVNS) because of bloody joint fluid by repeated puncture. T2*WIMRI depict marked low signal intensity along with articular capsule with so-called blooming artifact. It is borne in mind that synovial membrane composes of fibrocyte-like cells which produce hyaluronic acid, monocyte-like cells which make clean, and fenestrated capillaries. PVNS compose of these cells, fibrous stroma produced by fibrocyte-like cells, and hemosiderin deposit from proliferative capillaries. The similar disease are listed as pigmented villo-nodular bursitis (PVNB) and pigmented villo-nodular tenosynovitis (PVNTS) which is termed as giant cell tumor of the tendon sheath. Blooming artifact by hemosiderin laden synovial tissue on T2*WIMRI is characteristic of PVNS, PVNB and PVNTS.
【References】
1.Young, B et al. (2006). Wheater's Functional Histology: A Text and Colour Atlas (5th ed.). Churchill Livingstone.
2.Wechalekar MD, et al. Utility of arthroscopic guided synovial biopsy in understanding synovial tissue pathology in health and disease states. World J. Orthop. 2014; 5 : 566–73
3.Fawcett, Don Wayne, Bloom and Fawcett a textbook of histology, 11th ed. Chapman & Hall, New York, 1994, pp.229-232.
4.Mark K, et al. Pigmented Villonodular Synovitis: Radiologic-Pathologic Correlation. RadioGraphics. 2008; 28(5):1493-51
5.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
6.Bravo S, et al. Pigmented Villonodular Synovitis. Radiol Clin North Am. 1996;34(2):311-26.
2022.2.21