Abstract: Background  Rosai-Dorfman disease (RDD), also known as sinus histiocytosis with massive lymphadenopathy (SHML), is a non-neoplastic histiocytic proliferation predominantly affecting lymph nodes, and usually presents with massive painless cervical lymphadenopathy accompanied by fever and weight loss. Extranodal involvement occurs in over 40% of patients; however, isolated extranodal disease without lymph node involvement is unusual. Although extranodal involvement has been reported in diverse sites, central nervous system manifestation, particularly in spinal cord is distinctly rare. It is a diagnostic challenge for radiologists and histopathologists to differentiate RDD from other spinal lesions because of its similarities in radiological and histological findings. Herein we describe a case of unusual isolated RDD in spinal cord. The radiology and clinicopathology of this lesion, as well as its differential diagnosis are discussed.  Methods  The clinical manifestation of a patient with intraspinal primary RDD occurring C_3-6 level was presented retrospectively. Gross resected mass was routinely paraffin-embedded and stained with hematoxylin and eosin. Dako EnVision immunohistochemical staining system was used to detect the tumor antigen expressions, including S-100 protein (S-100), CD1a and CD68 (KP-1).  Results  A 25-year-old female patient presented with 3-month history of numbness and weakness in both upper limbs associated with an increasing neck back pain. There was no fever and lymphadenopathy found in the patient. MRI of the whole spine revealed a subdural mass extending from C₃ to C₆ level of cervical spinal cord with homogeneous enhancement after contrast administration. Laminectomy and midline opening of the dura were performed. The subdural lesion appeared to have no capsule and attach the dura mater. The lesion was removed totally. Under the microscopic examination, dense fibrosis and intense chronic inflammation with focal neutrophilic infiltrates were noted. The clusters of large histiocytes with eosinophilic, finely granular cytoplasm and multinucleate giant cells were also observed in the lesion. Emperipolesis with intact lymphocytes within the cytoplasm of the large histiocytes were present. Mitotic activity and necrotic area were not observed. Special stains for organisms were negative. By immunohistochemical analysis, the characteristic histiocytes were positive for S-100 and CD68 and negative for CD1a. Based on clinical presentations and histological findings, a final histological diagnosis of primary RDD in spinal cord was made according to the criteria of WHO classification. The patient did not receive chemotherapy and radiotherapy, and attended follow-up for 12 months, without any neurological deficit or signs of recurrence.  Conclusions  Isolated intraspinal RDD is rare. The definite diagnosis of this lesion should be made under the microscopical examination because the preoperative radiological appearance of the lesion does not differ from other lesions occurring in spinal cord, such as inflammatory pseudotumor, meningioma and lymphoma. Although good prognosis is obtained from gross total resection in most of reported patients with this lesion, recurrence could be found in individual cases, and chemotherapy and (or) radiotherapy had been applied for a few cases with multiple organs involvement to control the progression of lesion. Due to the rarity of its site, the strictly differential diagnosis should be made when the isolated RDD is encountered in spinal cord.

Key words: Histiocytosis, sinus, Cervical vertebrae, Spinal canal, Immunohistochemistry, Pathology

摘要： 研究背景 Rosai-Dorfman 病又称窦组织细胞增生症伴巨大淋巴结病，是一种主要累及淋巴结的非肿瘤性组织细胞增生性病变，临床表现为无痛性颈部淋巴结肿大、发热和体重下降；约40%的患者可同时累及结外组织，但仅有结外病灶而不伴淋巴结病变的结外Rosai-Dorfman 病临床鲜见，影像学检查易误诊为脑（脊）膜瘤或淋巴瘤，组织病理学易与炎症混淆。本文重点探讨椎管内原发性结外Rosai-Dorfman 病的影像学和临床病理学特征，并通过文献复习，分析其诊断要点，以期提高鉴别诊断能力。方法与结果 女性患者，25 岁。临床表现为进行性双上肢无力、麻木，颈部疼痛3 月余，不伴发热和淋巴结肿大。颈部MRI显示，C_{3 ~ 6}节段椎管内硬脊膜下占位性病变，T₁WI等信号、T₂WI不均匀低信号，增强后病灶呈明显均匀强化。术中可见病灶位于硬脊膜下，无包膜，与周围组织分界清楚，血运丰富，与硬脊膜关系密切，全切除肿瘤。术后组织病理学观察，纤维组织增生伴大量以淋巴细胞和浆细胞为主的炎性细胞浸润，也可见灶性中性粒细胞；不规则巢团状或片状分布的“浅染区”内可见呈簇状或弥漫片状分布的胞质空亮的大多角形细胞，体积巨大，胞质丰富，嗜酸性或淡染，胞核居中，圆形或卵圆形，浅染空泡状，可见小的嗜碱性核仁，胞质中可见“伸入现象”。大多角形细胞S-100 蛋白和CD68 表达阳性、CD1a表达阴性。病理诊断为椎管内原发性结外Rosai-Dorfman 病。结论 椎管内原发性结外Rosai-Dorfman 病极为少见，由于影像学表现缺乏特异性，术前易误诊为脑（脊）膜瘤或淋巴瘤，须经组织病理学明确诊断。尽管大多数中枢神经系统结外Rosai-Dorfman 病患者手术全切除病灶后预后良好，但术后仍可复发，术后放射治疗和（或）药物化疗可用于部分多器官受累患者以控制病情进展。由于发病部位少见，临床应提高对该病的警惕性，并注意与其他具有相似组织学结构的脊髓病变的鉴别。

关键词: 组织细胞增多症, 窦, 颈椎, 椎管, 免疫组织化学, 病理学