Shek T W, Ho F C, Ng I O, Chan A C, Ma L, Srivastava G
Department of Pathology, University of Hong Kong, Queen Mary Hospital, Hong Kong.
Am J Surg Pathol. 1996 Mar;20(3):313-24. doi: 10.1097/00000478-199603000-00008.
Tumors of the follicular dendritic cell are uncommon, and most occur as primary lymph node tumors. We report a case of primary follicular dendritic cell tumor of the liver that was initially reported as an inflammatory pseudotumor. The neoplasm recurred as two separate tumor masses 30 months after complete resection of the "hepatic inflammatory pseudotumor." It showed a wide spectrum of morphologic features ranging from areas with fascicles of very bland spindle cells amidst a background population of lymphocytes, reminiscent of inflammatory pseudotumor, to areas of dispersed sheets of highly pleomorphic tumor cells with a relative paucity of reactive inflammatory cells. The diagnosis was confirmed by positive immunohistochemical staining with CD21, CD35, R4/23, and Ki-M4 and by ultrastructural demonstration of convoluted interdigitating cell processes joined by desmosomes. The background lymphocytes were oligoclonal, CD8-positive T cells. In situ hybridization for Epstein-Barr virus (EBV)-encoded RNA was positive in the tumor cells in the original and recurrent tumors. More importantly, the cells showed identical episomal clonal EBV on Southern blot analysis, implying that the initial and recurrent tumors are due to clonal proliferation of EBV-positive neoplastic follicular dendritic cells. The tumor cells expressed latent membrane protein but not EBV-encoded nuclear antigen 2 (EBNA2) or ZEBRA. Such gene expression is very similar to that of Hodgkin's disease and nasopharyngeal carcinoma. The strong expression of latent membrane protein restricted to the tumor cells and the clonality of the EBV suggest that the virus may be involved in the pathogenesis of this tumor and not present merely as a "bystander."
滤泡树突状细胞瘤并不常见，大多数表现为原发性淋巴结肿瘤。我们报告一例肝脏原发性滤泡树突状细胞瘤，该病例最初被报告为炎性假瘤。在“肝脏炎性假瘤”完全切除30个月后，肿瘤复发为两个独立的肿块。它表现出广泛的形态学特征，从淋巴细胞背景中存在非常温和的梭形细胞束的区域，让人联想到炎性假瘤，到高度多形性肿瘤细胞分散成片且反应性炎性细胞相对较少的区域。通过CD21、CD35、R4/23和Ki-M4免疫组化染色阳性以及通过桥粒连接的卷曲指状细胞突起的超微结构证实了诊断。背景淋巴细胞为寡克隆性CD8阳性T细胞。原位杂交检测爱泼斯坦-巴尔病毒（EBV）编码的RNA在原发肿瘤和复发肿瘤的肿瘤细胞中均为阳性。更重要的是，在Southern印迹分析中，细胞显示出相同的游离型克隆性EBV，这意味着原发肿瘤和复发肿瘤是由于EBV阳性的肿瘤性滤泡树突状细胞的克隆性增殖所致。肿瘤细胞表达潜伏膜蛋白，但不表达EBV编码的核抗原2（EBNA2）或ZEBRA。这种基因表达与霍奇金淋巴瘤和鼻咽癌非常相似。潜伏膜蛋白仅在肿瘤细胞中强烈表达以及EBV的克隆性表明该病毒可能参与了该肿瘤的发病机制，而不仅仅是“旁观者”。
