Thway Khin, Wang Jayson, Swansbury John, Min Toon, Fisher Cyril
Sarcoma Unit, Royal Marsden Hospital, London SW3 6JJ, UK.
Department of Histopathology, Royal Marsden Hospital, London SW3 6JJ, UK.
Sarcoma. 2015;2015:812089. doi: 10.1155/2015/812089. Epub 2015 Feb 25.
Background. The assessment of MDM2 gene amplification by fluorescence in situ hybridization (FISH) has become a routine ancillary tool for diagnosing atypical lipomatous tumor (ALT)/well-differentiated liposarcoma and dedifferentiated liposarcoma (WDL/DDL) in specialist sarcoma units. We describe our experience of its utility at our tertiary institute. Methods. All routine histology samples in which MDM2 amplification was assessed with FISH over a 2-year period were included, and FISH results were correlated with clinical and histologic findings. Results. 365 samples from 347 patients had FISH for MDM2 gene amplification. 170 were positive (i.e., showed MDM2 gene amplification), 192 were negative, and 3 were technically unsatisfactory. There were 122 histologically benign cases showing a histology:FISH concordance rate of 92.6%, 142 WDL/DDL (concordance 96.5%), and 34 cases histologically equivocal for WDL (concordance 50%). Of 64 spindle cell/pleomorphic neoplasms (in which DDL was a differential diagnosis), 21.9% showed MDM2 amplification. Of the cases with discrepant histology and FISH, all but 3 had diagnoses amended following FISH results. For discrepancies of benign histology but positive FISH, lesions were on average larger, more frequently in "classical" (intra-abdominal or inguinal) sites for WDL/DDL and more frequently core biopsies. Discrepancies of malignant histology but negative FISH were smaller, less frequently in "classical" sites but again more frequently core biopsies. Conclusions. FISH has a high correlation rate with histology for cases with firm histologic diagnoses of lipoma or WDL/DDL. It is a useful ancillary diagnostic tool in histologically equivocal cases, particularly in WDL lacking significant histologic atypia or DDL without corresponding WDL component, especially in larger tumors, those from intra-abdominal or inguinal sites or core biopsies. There is a significant group of well-differentiated adipocytic neoplasms which are difficult to diagnose on morphology alone, in which FISH for MDM2 amplification is diagnostically contributory.
背景。通过荧光原位杂交（FISH）评估MDM2基因扩增已成为专科肉瘤中心诊断非典型脂肪瘤性肿瘤（ALT）/高分化脂肪肉瘤和去分化脂肪肉瘤（WDL/DDL）的常规辅助手段。我们描述了在我们的三级医疗机构使用该方法的经验。方法。纳入所有在两年期间通过FISH评估MDM2扩增的常规组织学样本，并将FISH结果与临床和组织学发现相关联。结果。来自347例患者的365份样本进行了MDM2基因扩增的FISH检测。170份为阳性（即显示MDM2基因扩增），192份为阴性，3份在技术上不满意。有122例组织学良性病例，组织学与FISH的符合率为92.6%，142例WDL/DDL（符合率96.5%），34例组织学上对WDL有疑问的病例（符合率50%）。在64例梭形细胞/多形性肿瘤（鉴别诊断包括DDL）中，21.9%显示MDM2扩增。在组织学与FISH结果不一致的病例中，除3例之外，所有病例的诊断均根据FISH结果进行了修正。对于组织学良性但FISH阳性的差异，病变平均更大，更常见于WDL/DDL的“经典”（腹腔内或腹股沟）部位，且更多为粗针活检。组织学恶性但FISH阴性的差异较小，较少见于“经典”部位，但同样更多为粗针活检。结论。对于组织学确诊为脂肪瘤或WDL/DDL的病例，FISH与组织学具有较高的符合率。在组织学不明确的病例中，尤其是缺乏明显组织学异型性的WDL或无相应WDL成分的DDL，特别是较大的肿瘤、来自腹腔内或腹股沟部位的肿瘤或粗针活检标本，FISH是一种有用的辅助诊断工具。有相当一部分高分化脂肪细胞性肿瘤仅靠形态学难以诊断，MDM2扩增的FISH检测对其诊断有帮助。
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