Objective: To investigate the clinicopathological features, special morphologic variants and potential diagnostic traps of classical follicular dendritic cell sarcoma (FDCS). Methods: A total of 25 cases of classical FDCS diagnosed in the First Hospital Affiliated to Army Medical University from 2006 to 2018 were examined by hematoxylin-eosin staining, immunohistochemistry and in situ hybridization for Epstein-Barr virus-encoded mRNA (EBER). Meanwhile, the types and characteristics of the special variants of FDCS were summarized along with those reported in the literature. Results: The age of patients ranged from 23 to 77 years (mean 52 years), the male to female ratio was 1.5, and the maximum diameter of tumor was 1.5 to 20 cm (mean 7.4 cm). Twelve cases (48%) were misdiagnosed at the initial evaluation. Follow-up information was available for 17 patients, and the follow-up time was 5 to 96 months. The propotion of patients having recurrence, metastasis and mortality was 3/17, 5/17 and 2/17, respectively. Microscopically, besides the typical morphology, 10 cases of FDCS showed special histomorphologies and/or structures, including those mimicking lymphoepithelioma-like carcinoma, desmoplastic infiltrating carcinoma, classical Hodgkin's lymphoma (CHL), anaplastic large cell lymphoma (ALCL) and hemangiopericytoma. These morphologic variants were potential diagnostic pitfalls and warranted attention. Immunohistochemistry showed that more than two markers of follicular dendritic cells (such as CD21, CD23, CD35, etc.) were expressed in cases showing typical morphology and the special variants. All 25 cases were all negative for EBER by in situ hybridization. Conclusions: Classical FDCS is rare, besides the typical morphologic features, there are many special variants. In particular, these may be confused with lymphoepithelioma-like carcinoma in the nasopharynx, CHL or ALCL in the mediastinum/lymph node. Awareness of these variants is essential for accurate diagnosis.
目的： 探讨经典型滤泡树突细胞肉瘤（FDCS）的临床病理特征、特殊变异形态及潜在诊断陷阱，提高诊断准确性。 方法： 对2006—2018年陆军军医大学第一附属医院诊断的25例经典型FDCS进行组织形态观察、免疫组织化学染色和EB病毒编码的小RNA（EBER）原位杂交检测，结合文献分析其特殊变异形态的类型和特点。 结果： 25例FDCS患者年龄23~77岁（平均52岁），男女比例为1.5∶1.0，肿瘤最大径1.5~20.0 cm（平均7.4 cm），其中12例（48%）在初次诊断时被误诊。17例有随访信息，随访时间5~96个月，复发、转移、病死比例分别为3/17、5/17、2/17。除了典型组织形态外，10例FDCS可见特殊的变异形态和/或组织结构，包括淋巴上皮癌样、促结缔组织增生性浸润癌样、霍奇金淋巴瘤样、间变性大细胞淋巴瘤样及血管外皮细胞瘤样等，是需要重视的潜在诊断陷阱。免疫组织化学染色结果显示典型形态和各种特殊的变异形态均可表达2个以上滤泡树突细胞标志物（CD21、CD23、CD35等）。EBER原位杂交检测显示25例FDCS均为阴性。 结论： 经典型FDCS罕见，除了典型的组织形态外还可出现多种特殊的变异形态，其中鼻咽部的淋巴上皮癌样、纵隔或淋巴结内的霍奇金淋巴瘤样、间变性大细胞淋巴瘤样变异型尤其值得我们重视。加强对此类罕见变异形态的认识，提高诊断警惕性，有助于避免误诊。.
Keywords: Dendritic cell, follicular; In situ hybridization; Sarcoma.