Department of Pathology and Laboratory Medicine, King Hussein Cancer Center, AMMAN, JORDAN.
Turk Patoloji Derg. 2021;37(2):172-177. doi: 10.5146/tjpath.2020.01507.
ALK positive histiocytosis is a relatively new histiocytic proliferation disease with a characteristic gene translocation involving fusion of the ALK gene with different partners, mostly KIF5B. We report a case of ALK-positive histiocytosis with literature review. A 27-year-old male patient presented mainly with progressive lower limb weakness. Imaging studies showed an intradural extramedullary enhancing lesion at the L3 level. A 1.5 cm mass was excised from the sensory nerve root in the filum terminale at the level of L3. Histologic examination showed infiltration of the nerve by numerous histiocytes with moderate to abundant eosinophilic to clear-foamy and variably-vacuolated cytoplasm with irregular-to-smooth contoured nuclei. The histiocytes were positive for CD68 and ALK1 and negative for S100 and CD1a. KIF5B-ALK fusion was detected by real time-polymerase chain reaction. The patient is asymptomatic nine months after surgical excision. This is the first reported localized case occurring in the nerve root of an adult patient, thus expanding the clinical manifestations of this disease. An integrated histological, immunohistochemical and molecular approach is recommended for diagnosis. We recommend performing ALK1 immunohistochemical stain on all histiocytosis cases to increase awareness and detection of this newly described entity.
ALK 阳性组织细胞增生症是一种相对较新的组织细胞增生性疾病，具有特征性的基因易位，涉及 ALK 基因与不同伴侣的融合，主要是 KIF5B。我们报告了一例 ALK 阳性组织细胞增生症，并进行了文献复习。一名 27 岁男性患者主要表现为进行性下肢无力。影像学检查显示 L3 水平硬膜外髓外增强病变。在 L3 水平终丝处从感觉神经根切除了 1.5 厘米的肿块。组织学检查显示大量组织细胞浸润神经，胞质中等至丰富嗜酸性，呈透明泡沫状，并有不同程度的空泡化，核不规则至光滑轮廓。组织细胞 CD68 和 ALK1 阳性，S100 和 CD1a 阴性。通过实时聚合酶链反应检测到 KIF5B-ALK 融合。患者在手术切除后九个月无症状。这是首例报告发生在成人神经根的局部病例，从而扩展了该疾病的临床表现。建议采用综合组织学、免疫组织化学和分子方法进行诊断。我们建议对所有组织细胞增生症病例进行 ALK1 免疫组织化学染色，以提高对这种新描述实体的认识和检测。
