History: A 47-year-old woman presented to an orthopedist for evaluation of chronic pain of her left knee for the past two to three years.
病史：47岁女性，左膝慢性疼痛2-3年。
Radiographs of the left knee were obtained. Frontal, lateral, and sunrise views are shown below.
左膝平片（正侧位、髌骨轴位）
An MRI exam of the left knee was subsequently performed. Axial T1-weighted, fat-saturated (FS) T2-weighted, gradient-recalled echo (GRE), coronal T1-weighted, sagittal and axial proton density FS, FS T1-weighted precontrast, axial FS T1-weighted postcontrast, and sagittal FS T1-weighted postcontrast images are shown below.
随后行左膝MR扫描，各序列图像如下所示。
Findings
Radiographs: There is no acute osseous abnormality. There is no radiopaque foreign body, joint effusion, or soft-tissue swelling. There is mild tricompartmental osteoarthritis.
MRI: There are imaging findings of diffuse pigmented villonodular synovitis extending into the joint recesses and also extending into a moderate-sized popliteal cyst.
影像表现：
平片：未见明显急性骨质异常，无不透射线的异物，无关节积液或软组织肿胀，可见轻度的骨关节炎。
MRI：表现为弥漫性的色素沉着绒毛结节性滑膜炎，其延伸到关节凹陷并延伸到中等大小的腘窝囊肿内。
Differential diagnosis
Pigmented villonodular synovitis
Gout
Hemophilic arthropathy
Amyloid
Synovial chondromatosis
鉴别诊断：
色素沉着绒毛结节性滑膜炎
痛风
血友病性关节病
淀粉样变
滑膜软骨瘤病
Diagnosis: Pigmented villonodular synovitis
诊断：色素沉着绒毛结节性滑膜炎
Pigmented villonodular synovitis (PVNS)
Pathophysiology 病理生理学
Pigmented villonodular synovitis refers to a rare, benign proliferative condition involving joint synovial membranes, bursae, and/or tendons. 色素绒毛结节性滑膜炎是指涉及关节滑膜，粘液囊和/或肌腱的一种罕见的良性增殖性病变。
Localized: Most common form and typically extra-articular (PVNB and GCTTS). 局限性：最常见的表现，典型的在关节外（PVNB和GCTTS）。
Diffuse: Most common form of intra-articular disease. However, localized intra-articular involvement also has been described. 弥漫性：关节内病变的最常见形式。 然而也可表现为局部的关节内受累。
Referred to as pigmented villonodular bursitis (PVNB) when in the bursa and giant cell tumor of the tendon sheath (GCTTS) when involving a tendon sheath. 当在滑液囊内，称为色素绒毛结节性滑囊炎（PVNB）；当累及腱鞘时，为腱鞘巨细胞瘤（GCTTS）。
The condition is divided into localized and diffuse forms. 可分为局灶性和弥散性。
Etiology is unknown, but cytogenetic abnormalities and autonomous growth suggest a likely neoplastic process. 病因尚不清楚，但细胞遗传学异常和自主生长提示其可能是一个肿瘤进程。
The abnormal synovium is predisposed to hemorrhage with trauma, leading to repeated hemorrhagic effusions and resulting in nodular formation and iron deposition in the synovium. 异常滑膜倾向于伴有外伤的出血，导致反复出血性渗出并导致滑膜中的结节形成和铁沉积。
It is most commonly monoarticular (approximately 70% of cases) and affecting large synovial surfaces. Most common locations for intra-articular PVNS: knee > ankle > hip > shoulder > elbow. 通常是单关节发病（大约70％的病例）并影响大的滑膜表面。关节内PVNS最常见的发病部位：膝>踝>髋>肩>肘。
PVNS is rare in the pediatric population, but it is more frequently polyarticular when seen. PVNS在儿童罕见，但当发生时常表现为多关节。
If left untreated, the disease will lead to repeated hemorrhage and proliferation, leading to joint destruction. 如果不及时治疗，该疾病将导致反复出血和增殖，从而导致关节破坏。
Malignant transformation is rare and can occur de novo or be associated with recurrent disease. Prevalence is approximately 3% of cases. 恶变非常罕见，可复发，其发生率约为3％。
Epidemiology 流行病学
Annual incidence is estimated at 9.2 (extra-articular) and 1.8 (intra-articular) cases per 1 million population. 每百万人口的年发病率约为9.2（关节外）和1.8（关节内）。
The condition accounts for 5% of all primary soft-tissue “tumors.' 占所有原发性软组织“肿瘤”的5%。
Intra-articular PVNS has a wide range of age of presentation. 关节内PVNS的发病年龄较广。
Most commonly occurs between 30 and 40 years of age. 最多见于30-40岁。
There is no sex predilection. 没有性别偏好。
Giant cell tumor of tendon sheaths: 腱鞘巨细胞瘤
Most commonly occurs between 30 and 50 years. 最多见于30-50岁。
There is no sex predilection. 没有性别偏好。
It is the second most common soft-tissue mass of the hand. 是第二常见的手部软组织肿物。
Clinical presentation 临床表现
Patients present with pain, swelling, and limited range of motion of the involved joint.患者可出现疼痛，肿胀和受累关节运动受限。
Effusion is typically grossly chocolate brown in color and may reaccumulate rapidly.渗出物通常呈巧克力色，可迅速重新累积。
Symptoms are usually present for many months before the diagnosis is made. 在诊断之前，症状通常会持续数月。
Imaging features 影像表现
Radiographs: 平片
PVNS:
May appear normal. 可表现正常。
May see a joint effusion. 可见关节积液。
Can see erosions of bone on both sides of the joint, but the joint space will typically remain unaffected. 可见关节两侧的骨侵蚀，但关节间隙通常不受影响。
Normal bone density and preserved cartilage are seen until late stages of involvement. 直到病变晚期，仍可见正常的骨密度和持续存在的软骨。
Calcification is typically not present. 通常不存在钙化。
GCTTS:
May see a soft-tissue mass generally on the volar aspect of the finger. 可表现为手指掌侧面的软组织肿物。
Can see pressure erosions of the underlying bone (15%). 可见邻近骨压迫性骨质侵蚀（15%）。
CT：
May see large subchondral cysts. 可见较大的软骨下囊肿。
Can see effusion and associated soft-tissue masses. 可见关节积液及软组织肿物。
Hypertrophic synovium may demonstrate increased attenuation secondary to hemosiderin deposition. 肥厚的滑膜可因含铁血黄素沉积而表现为密度增加。
Synovium enhances after contrast administration. 增强后滑膜有强化。
Calcification is typically not present. 一般无钙化。
Can see erosions of bone on both sides of the joint, particularly in less capacious joints such as the hip. 可见关节两侧的骨侵蚀，尤其在髋关节等容积较小的关节中。
MRI：
T1-weighted imaging: Appears with homogeneously low to intermediate signal. T1WI：表现为均匀的低至等信号。
T2-weighted/fluid-sensitive sequences: Appears with predominantly low to intermediate signal. May see some areas of high signal due to joint fluid or inflamed synovium. T2WI（液体敏感序列）：主要表现为低至等信号，由于关节积液或滑膜炎症可见一些高信号区域。
GRE: Blooming is seen due to the presence of hemosiderin. GRE：由于含铁血黄素存在而呈低信号。
Postcontrast imaging: Moderate to marked inhomogeneous enhancement is seen. 增强扫描：可见中等至明显不均质强化。
May increase conspicuity for assessment of lesion extent. 可提高病变程度评估
的显著性。
Treatment 治疗
Requires resection with complete synovectomy. 需要行完全滑膜切除。
Incomplete resection has a high recurrence rate; overall recurrence rate is 20% to 50%. 不完全切除将有较高的复发率，总的复发率在20%-50%。
May require an open surgical procedure, as an arthroscopic technique may not reach some lesions. 需要行开放式手术，因为关节镜技术可能无法达到某些病变。
Adjuvant treat is often recommended with radiation and sometimes with intra-articular injection of yttrium-90. 辅助治疗通常建议使用放疗，有时还需要关节内注射钇-90。
Medical therapy is being investigated. 药物治疗还在研究中。
Refractory cases may require arthroplasty or arthrodesis. 难治性病例可能需要关节成形术或关节固定术。
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