脾脏炎性假瘤样滤泡树突细胞肿瘤的临床病理学特征

Inflammatory pseudotumor-like follicular dendritic cell tumor of spleen

目的探讨炎性假瘤样滤泡树突细胞肿瘤的临床病理学特征。方法观察1例脾脏的炎性假瘤样滤泡树突细胞肿瘤的大体和光镜形态，免疫组织化学EnVision法检测CD21、CD23、CD35、Clusterin、S-100、波形蛋白、平滑肌肌动蛋白（SMA）、CD1a、CD68、间变型淋巴瘤激酶（ALK）、CD30、CD31、CD34、CD3、CD20，原位杂交检测EBER，并结合文献复习分析其生物学行为和病因机制。结果炎性假瘤样滤泡树突细胞肿瘤好发于腹腔内脏器，尤以肝、脾多见，患者以女性为主。一般肿瘤较大，切面灰白质韧，中心有出血或坏死。镜下大量淋巴细胞、浆细胞背景中见弥散分布的滤泡树突细胞，形似炎性假瘤。高倍镜下滤泡树突细胞胞质淡染，胞界不清，核卵圆形或杆状，染色质空泡样或点彩状，居中可见小的紫色核仁。部分瘤细胞显示异型性，核膜皱褶，染色质粗糙，核仁明显。核分裂象罕见。免疫组织化学：梭形瘤细胞波形蛋白强阳性；Clusterin、SMA、CD68均阳性；CD35局部弱阳性，S-100弱阳性；CD21、CD23、CD1a、ALK、CD30、CD31、CD34均阴性。背景淋巴细胞CD3阳性，灶性区CD20阳性。原位杂交：梭形瘤细胞EBER阳性。结论炎性假瘤样滤泡树突细胞肿瘤是一种罕见的低度恶性肿瘤，与EB病毒感染有关。

Objective To study the clinicopathologic features of inflammatory pseudotumor-like follicular dendritic cell tumor of spleen. Methods One case of inflammatory pseudotumor-like follicular dendritic cell tumor of spleen was examined macroscopically and microscopically. Immunohistochemical study for CD21, CD23, CD35, clusterin, S-100 protein, vimentin, smooth muscle actin, CDla, CD68, ALK protein, CD30, CD31, CD34, CD3 and CD20 was performed on formalin-fixed, paraffin-embedded sections by standard EnVision method. In-situ hybridization for Epstein-Barr virus （EBV）-encoded RNA was also carried out. Results Macroscopically, inflammatory pseudotumor-like follicular dendritic cell tumor was large in size, tan-colored, soft to rubbery in consistance and associated with central hemorrhage and necrosis. Histological examination showed scattered follicular dendritic cells admixed with abundant lymphocytes and plasma cells in the background, simulating inflammatory pseudotumor. On high-power magnification, the follicular dendritic cells possessed a moderate amount of pale to lightly eosinophilic cytoplasm, with indistinct cell borders. The nuclei were ovoid or spindly, with vesicular or stippled chromatin and small distinct, often centrally located, nucleoli. Some of the tumor cells showed nuclear pleomorphism and contained irregular foldings of nuclear membrane, coarse chromatin and prominent eosinophilic nucleoli. Mitotic figures were rarely identified. Immunohistochemical study showed that the tumor cells were positive for vimentin, clusterin, smooth muscle actin and CD68. They were weakly and focally positive for CD35 and S-100 protein, but negative for CD21, CD23, CD1a, ALK protein, CD30, CD31 and CD34. Most of the background lymphocytes were of T-lineage （CD3-positive） ,some were CD20 （B-cell marker）-positive. EBV RNA was demonstrated in the tumor cells by in-situ hybridization analysis. Conclusions Inflammatory pseudotumor-like follicular dendritic cell tumor is a rarely encountered low-grade malignancy with distinctive morphologic pattern. It is associated with EBV infection.