History: A 15-year-old female distance runner presents with intermittent right knee pain that she\’s had for the past three months.
病史：一名15岁的女子长跑运动员在过去的三个月里出现了间歇性右膝疼痛。
Frontal and lateral radiographs of the right knee are shown below. 右膝正侧位片如下所示。
Additional history: The patient was initially treated with conservative management. The pain persisted and slowly worsened over the next three months. The patient was subsequently evaluated with a nuclear medicine study.
补充病史：患者最初接受保守治疗。 在接下来的三个月里，疼痛持续并缓慢恶化。 随后对患者行核医学检查。
Frontal and posterior whole-body scintigrams and spot views of the knees are shown below. 全身前后位及右膝局部放大骨扫描图如下。
MR images
An MRI scan of the right knee with and without contrast was performed. In order: T1-weighted and short tau inversion-recovery (STIR) images and “water lava flex” pre- and postcontrast images.
行右膝MRI平扫 增强扫描。分别为：T1WI、T2-STIR、平扫 增强图像。
Additional history: The patient\’s knee effusion was aspirated and demonstrated the following results:
病史补充：吸取患者的膝关节积液，化验结果如下：
- Greater than 250,000 red blood cells 大于250,000个红细胞
- 180 white blood cells (predominantly lymphocytes) 180个白细胞（主要是淋巴细胞）
Staging studies: Staging studies, including F-18 FDG PET/CT, were negative. No other suspicious lesions were identified.
分期研究：包括F-18 FDG PET / CT在内的分期研究均为阴性。 没有发现其他可疑病变。
Findings
- Radiographs: Within normal limits.
- Bone scan: Focal increased osteoblastic activity is seen within the distal right femur.
- MRI: Bone marrow-occupying mass is seen within the distal right femur. It is hypointense to marrow on T1-weighted sequences and hyperintense on STIR sequences. The mass demonstrates mild heterogeneous enhancement with regions of central nonenhancement. There is also surrounding periosteal enhancement.
影像表现：
- 平片：未见明显异常；
- 骨扫描：右股骨远端可见成骨细胞活动增加。
- MRI：在右股骨远端可见骨髓内被肿物占据。 在T1WI上信号低于骨髓，在STIR序列上呈高信号。增强扫描呈轻度不均质强化，中央可见无强化区，周围骨膜有强化。
Differential diagnosis
- Primary bone lymphoma
- Ewing sarcoma
- Metastatic disease
- Secondary osseous lymphoma
- Osteomyelitis
鉴别诊断：
- 原发性骨淋巴瘤
- 尤文氏肉瘤
- 转移瘤
- 继发性骨淋巴瘤
- 骨髓炎
Diagnosis: Primary non-Hodgkin\’s lymphoma of the bone, diffuse large B-cell type
最后诊断：骨原发性非霍奇金淋巴瘤（弥漫大B细胞型）
Key points
Primary bone lymphoma
原发性骨淋巴瘤
Pathophysiology
- Primary bone lymphoma is an extranodal lymphoma that arises from the medullary cavity.
- The cause is unknown. Possible causes that have been suggested include inherited factors, immunodeficiency, viral infection, organ transplantation, and Paget’s disease of the bone.
- Majority of cases are non-Hodgkin\’s lymphoma of B-cell origin.
病理生理学
- 原发性骨淋巴瘤是起源于髓腔的结外淋巴瘤。
- 病因不明，已经提出的可能性病因包括遗传因素，免疫缺陷，病毒感染，器官移植和骨佩吉特病。
- 多数病例是B细胞来源的非霍奇金淋巴瘤（NHL）。
Epidemiology
- It is a rare condition.
- It comprises 3% of primary malignant bone tumors and 1% of all malignant lymphomas.
- It occurs in a broad age range of patients with the majority of cases in patients older than 45 years old.
- There is a slight male predominance (male-to-female ratio: 1.8:1.2).
- Favors long bones with persistent bone marrow: The femur is the most affected site (50%). The pelvis is the second most common site (20%).
流行病学
- 是一种罕见病；
- 占原发恶性骨肿瘤的3％，占所有恶性淋巴瘤的1％；
- 发病年龄较广，大部分见于45岁以上的患者；
- 男性略占优势（男女比例为1.8：1.2）。
- 主要累及长骨骨髓：股骨是最常见的部位（50％），骨盆是第二常见的部位（20％）。
Clinical presentation
- Common presentation symptoms include local bone pain (insidious and intermittent that may persist for months), soft-tissue swelling, mass, pathologic fracture, or hypercalcemic crisis.
- Classic B symptoms are rare.
- Diagnosis implies the absence of nodal or disseminated disease.
临床表现
- 常见症状包括局部骨痛（隐匿性和间歇性，可能持续数月），软组织肿胀，肿块，病理性骨折或高钙血症危象；
- 经典B症状很少见；
- 原发性的诊断意味着没有淋巴结或播散性疾病。
Imaging features
Radiographs — variable appearance:
- Near-normal
- Focal lytic lesion with geographic margins
- Mixed lytic-sclerotic lesion
- Permeative process with cortical destruction and soft-tissue extension
MRI:
- Low signal on T1-weighted imaging
- High signal on T2-weighted imaging — Regions of fibrosis will have low T2 signal.
- Regions of enhancement on postcontrast imaging
- Bone marrow
- Soft-tissue involvement — Often seen with lesions that demonstrate a permeative pattern on radiographs.
- Cortical erosion
Bone scan:
- 98% demonstrate increased radiotracer uptake.
- Useful for staging.
影像表现：
平片（表现不一）：
- 接近正常；
- 局灶性溶骨性病变，“地图样”边缘；
- 溶骨-硬化混合性病变；
- 浸润性病变并骨皮质破坏和软组织肿胀。
MRI：
- T1WI低信号；
- T2WI高信号，局部纤维成分可表现为低信号；
- 增强后局部有强化；
- 发生在骨髓内；
- 软组织受累；
- 骨皮质破坏。
骨扫描：
- 98%表现为放射性示踪剂摄取增加；
- 可用于分期。
Treatment
- There is no standard consensus on a therapy regimen.
- Treatment is predominantly with chemotherapy, radiotherapy, or a combination of chemotherapy followed by adjuvant radiation therapy.
- Studies have shown improved survival with a combination chemotherapy and radiation therapy compared with chemotherapy or radiation therapy alone.
治疗：
- 治疗方案没有标准共识；
- 治疗方法主要是化疗，放疗或化疗联合辅助放疗；
- 研究表明，联合化疗和放射治疗与单独化疗或放疗相比，生存率有所提高。