双语病例丨原发性骨平滑肌肉瘤 （X/MR/PET）

History: A 43-year-old woman presents with knee pain after feeling a popping sensation while playing tennis.

病史：43岁女性，打网球时感觉到砰的感觉，膝部疼痛。

Radiographs were obtained. 平片如下所示。

问答：

There is a lesion in the proximal tibia with a benign appearance.

• True

• False (correct!)

胫骨近端病灶呈良性表现。答：错误。

The lesion in the proximal tibia has aggressive features, including an infiltrative appearance and ill-defined margins.

胫骨近端病灶有侵袭性，呈浸润性表现，边界模糊。

MR images

An MRI scan of the knee was performed. Intravenous contrast was not administered due to acute kidney injury. Coronal T1-weighted nonfat-saturated and T2-weighted fat-saturated images are shown below.

行膝关节MR扫描。由于急性肾损伤未行增强扫描。冠状T1WI非压脂及T2WI压脂图像如下所示。

问答

What is the next step? 下一步该做什么？

• Short-term imaging follow-up 短期随访

• No additional follow-up required 无需随访

• Biopsy (correct!)  活检（正确答案）

Additional questions

Biopsy of the tibial lesion revealed a pathologic diagnosis of leiomyosarcoma.

胫骨病变活检，病理诊断为：平滑肌肉瘤。

Primary bone leiomyosarcomas are common primary bone malignancies.

• True

• False (correct!)

原发性骨平滑肌肉瘤是常见的原发性骨恶性肿瘤。（说法错误）

Which of the following is more likely? 下列那种情况最可能？

• Primary bone leiomyosarcoma 原发性骨平滑肌肉瘤

• Leiomyosarcoma metastasis to bone (correct!) 平滑肌肉瘤转移至骨骼（正确）

Pelvic MR images

An MRI scan of the pelvis was performed. Sagittal and axial T2-weighted images are shown.

盆腔MR图像：行盆腔MR扫描，矢状及轴位T2WI图像如下所示。

The uterine findings are highly suspicious for uterine leiomyosarcoma.

• True

• False (correct!)

子宫的表现应高度怀疑为子宫平滑肌肉瘤（说法错误）。

There are typical findings of small benign leiomyomas. However, small leiomyosarcomas can have the same appearance as benign leiomyomas.

为小良性平滑肌瘤的典型表现，然而，小的平滑肌肉瘤可能与良性平滑肌瘤有着同样的表现。

PET/CT images

A whole-body FDG-PET/CT scan was performed. Fused CT/PET images are shown (axial pelvis and coronal knees). 

行全身PET/CT，CT/PET融合图像如下所示（盆腔轴位、膝部冠状）

The right proximal tibial lesion shows avid FDG uptake.

• True (correct!)

• False

右胫骨近端病灶可见明显FDG摄取（说法正确）。

The uterus shows a lesion with avid FDG uptake.

• True

• False (correct!)

子宫病灶可见明显FDG摄取（说法错误）。

Additional questions

Because uterine leiomyosarcomas are much more common than primary bone leiomyosarcomas, the patient underwent a hysterectomy to evaluate for a primary uterine leiomyosarcoma. On pathologic evaluation, the uterus had only benign findings.

其他问题

由于子宫平滑肌肉瘤比原发性骨平滑肌肉瘤更常见，患者接受了子宫切除术以评估是否为原发性子宫平滑肌肉瘤。最后病理诊断只有良性发现，为子宫平滑肌瘤。

Primary bone leiomyosarcomas have a distinct histologic appearance to leiomyosarcomas arising from other sites.

• True

• False (correct!)

原发性骨平滑肌肉瘤与其他部位的平滑肌肉瘤有不同的组织学表现（说法错误）。

Primary bone leiomyosarcomas most commonly occur in the spine.

• True

• False (correct!)

They most commonly occur in the appendicular skeleton.

原发性骨平滑肌肉瘤最常见于脊柱（说法错误），最常见于四肢骨。

Primary bone leiomyosarcomas have a distinct radiologic appearance when compared with other primary bone sarcomas.

• True

• False (correct!)

与其他原发骨肉瘤相比，原发性骨平滑肌肉瘤有着不同的影像学表现（说法错误）。

Findings

• Radiographs: Located centrally within the proximal tibia is an infiltrative mixed sclerotic and lytic lesion, which appears to have cortical breakthrough along the tibial plateau.

• Knee MRI: A large infiltrative lesion is present within the proximal tibia that has replaced the normal fatty marrow and has intrinsic T1 signal isointense to muscle. On the T2-weighted image, the lesion has heterogeneously high intrinsic T2 signal.

• Pelvic MRI: T2 hypointense lesions are present arising from the uterine myometrium, most consistent with benign leiomyomas.

• FDG-PET/CT: Avid FDG uptake is seen within the proximal right tibial lesion. No abnormal uptake is seen within the pelvis. Although images are not shown, no other abnormal FDG uptake is seen in the remainder of the body.

影像表现：

• 平片：胫骨近端中心性的浸润性的硬化和溶解混合性病变，病变突破了胫骨平台骨皮质。

• 膝关节MRI：近端胫骨内较大的浸润性病变，已经取代了正常的脂肪骨髓，T1WI上与肌肉等信号，T2WI上呈不均匀高信号。

• 盆腔MRI：子宫肌层内T2低信号灶，与良性平滑肌瘤的表现最为一致。

• FDG-PET / CT：在右侧胫骨损伤部位可见FDG摄取。骨盆内未见异常摄取。尽管没有显示图像，但在身体的其余部分没有看到异常的FDG摄取。

Differential diagnosis

• Primary bone leiomyosarcoma

• Metastasis

• Multiple myeloma

• Primary bone sarcoma

• Lymphoma

鉴别诊断：

• 原发性骨平滑肌肉瘤

• 转移瘤

• 多发性骨髓瘤

• 原发性骨肉瘤

• 淋巴瘤

Diagnosis: Primary bone leiomyosarcoma (pathology-confirmed)

最后诊断：原发性骨平滑肌肉瘤（病理证实）

Discussion  讨论

Primary bone leiomyosarcoma (PBL)

原发性骨平滑肌肉瘤（PBL）

Pathophysiology and epidemiology

Primary bone leiomyosarcomas are extremely rare primary osseous malignancies, with fewer than 200 cases reported in the literature. Only case reports and small case series have been reported, making comments on epidemiology somewhat difficult. These tumors occur in adults, with conflicting reports on an age predilection. There appears to be an equal distribution between sexes. They most commonly occur in the appendicular skeleton.

Pathologically, primary bone leiomyosarcomas are thought to arise from intraosseous blood vessels or possibly intraosseous pluripotent mesenchymal stem cells. They are a type of spindle cell bone sarcoma. Interestingly, they are histologically identical to primary leiomyosarcomas arising in other sites in the body (uterus, retroperitoneum, etc.). These tumors are so rare that when encountered they are likely classified as other types of primary bone sarcomas (i.e., undifferentiated pleomorphic sarcoma, fibrosarcoma, etc). Also, given their rarity, other more common sites of leiomyosarcoma (gynecologic, retroperitoneum, soft tissues) must first be excluded.

病理生理学和流行病学

原发性骨平滑肌肉瘤是非常罕见的原发性骨恶性肿瘤，文献报道少于200例，只有病例报告和小病例系列报道，使流行病学评论有些困难。这些肿瘤发生在成年人身上，有关年龄偏好的报道相互矛盾。男女发病率基本持平。

肿瘤最常见于附肢骨骼中。↓

病理上，原发骨平滑肌肉瘤被认为是由骨内血管或骨内多能间充质干细胞产生的。是一种梭形细胞骨肉瘤。有趣的是，它们在组织学上与体内其他部位（子宫，腹膜后等）中产生的原发性平滑肌肉瘤相同。这些肿瘤非常罕见，常可能被归类为其他类型的原发性骨的肉瘤（即未分化的多形性肉瘤，纤维肉瘤等）。此外，鉴于其稀有性，首先必须排除其他更常见的平滑肌肉瘤（妇科、腹膜后、软组织）。

Clinical presentation

Clinically, most patients present with pain. A significant proportion of patients also present with pathologic fracture. 

临床表现

临床上大多数患者表现出疼痛。相当一部分患者也存在病理性骨折。

Imaging features

• Radiographs：On radiographs, primary bone leiomyosarcomas are generally osteolytic lesions with aggressive features, including irregular and infiltrative margins and a permeative appearance. Cortical erosions and breakthrough can occur. They generally arise from the metaphysis but can extend into both the epiphysis and diaphysis.

• CT：CT findings are similar to radiographic findings, with the exception that cortical involvement is better evaluated.

• MRI：MR findings are generally nonspecific, with intrinsic T1 signal often similar to muscle and intrinsic T2 signal that is often heterogeneously high.

影像表现：

• X线片：原发骨平滑肌肉瘤一般表现为具有侵蚀性特征的溶骨性病变，包括不规则的形态、浸润性的边缘，以及渗透性的表现，可出现皮质侵蚀和突破。 它们通常起源于干骺端，但可以延伸到骨骺和骨干。

• CT：CT表现与X线相似，不同之处在于能更好地评估骨皮质受累的情况。

• MRI：MR表现一般无特异性，其内T1信号通常与肌肉相似，T2WI上通常呈不均质高信号。

Treatment

Before treatment is started, metastasis from a separate primary leiomyosarcoma (most commonly gynecologic or retroperitoneal in origin) must be excluded. The primary mode of treatment is wide surgical excision, often taking the form of amputation. Chemotherapy and radiation treatment also have been used. However, given the rarity of primary bone leiomyosarcomas, definitive chemoradiation regimens have not been established. Similar to other sarcomas, the most common site of metastasis is the lungs, though osseous metastasis also is common. 

治疗：

在治疗开始之前，必须排除是否为原发性平滑肌肉瘤（最常见的是妇科或腹膜后）的转移。 主要的治疗方式是广泛的手术切除，通常采取截肢的形式。化疗和放疗也已被使用。 然而，鉴于原发性骨平滑肌肉瘤的罕见性，确定的化放疗方案尚未建立。与其他肉瘤类似，最常见的转移部位是肺部，骨转移也较常见。

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