BACKGROUND 99mTc-labelled methylene diphosphonate (99mTc-MDP) uptake can occasionally be identified in extraosseous neoplasms on whole-body scans (WBSs) and may be misinterpreted as bone metastasis. The purpose of our study was to investigate the frequency of 99mTc-MDP uptake in extraosseous neoplasms and to assess the additional value of SPECT/CT for the localization and characterization of this unusual uptake. METHODS Data from 7308 patients (SPECT/CT was performed in 2147 patients) with known cancer who underwent WBSs for metastatic work-up between May 2015 and July 2018 were retrospectively reviewed. The locations, numbers, and intensities of extraosseous 99mTc-MDP uptake were evaluated by WBS, and the intratumoural calcification was evaluated by SPECT/CT. The diagnostic accuracy of SPECT/CT in locating 99mTc-MDP uptake in extraosseous neoplasms was compared to that of WBS. RESULTS A total of 41 patients showed 99mTc-MDP uptake in extraosseous neoplasms. Of these patients, 23 patients had uncertain lesions by WBS, and further SPECT/CT was performed. The incidence of 99mTc-MDP uptake in extraosseous neoplasms was observed to be 0.6% by WBS and 1.1% (by) SPECT/CT. During imaging analysis, WBS had an accuracy of only 35% (14/40), whereas SPECT/CT correctly located and diagnosed all 40 lesion sites in the 23 patients. Twenty-three lesion sites (57.5%, 23/40) showed moderate or high intensity of extraosseous 99mTc-MDP uptake. Of the 23 patients, 17 patients (73.9%, 18/23) with 31 lesion sites (77.5%, 31/40) presented with intratumoural calcification. CONCLUSIONS 99mTc-MDP uptake in extraosseous neoplasms can be observed as 0.6% on WBS and is usually localized to the breast, liver, and lung. Nuclear physicians should be familiar with such extraosseous uptake when interpreting WBSs. SPECT/CT offers better accuracy than WBS alone for locating the majority of lesions present with intratumoural calcification.

中文翻译：

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全身骨扫描中模拟骨转移的骨外肿瘤中99mTc-MDP摄取的准确表征：SPECT / CT的贡献。

背景技术有时在全身扫描（WBS）的骨外肿瘤中可以识别出99mTc标记的二膦酸二甲酯（99mTc-MDP）摄取，并且可能被误解为骨转移。我们研究的目的是调查骨外赘生物摄取99mTc-MDP的频率，并评估SPECT / CT对这种异常摄取的定位和表征的附加价值。方法回顾性分析2015年5月至2018年7月接受WBS转移检查的7308例已知癌症患者的数据（SPECT / CT在2147例患者中进行）。WBS评估骨外99mTc-MDP摄取的位置，数量和强度，SPECT / CT评估肿瘤内钙化。将SPECT / CT在骨外肿瘤中定位99mTc-MDP摄取的诊断准确性与WBS进行了比较。结果共有41例患者在骨外肿瘤中摄取了99mTc-MDP。在这些患者中，有23例通过WBS的病灶不确定，并进行了进一步的SPECT / CT检查。WBS观察到骨外肿瘤摄取99mTc-MDP的发生率为0.6％，SPECT / CT观察为1.1％。在影像分析期间，WBS的准确度仅为35％（14/40），而SPECT / CT可以正确定位并诊断23例患者中的所有40个病变部位。23个病变部位（57.5％，23/40）显示出中等或高强度的骨外99mTc-MDP摄取。在这23例患者中，有31个病变部位（77.5％，31/40）的17例患者（73.9％，18/23）表现为肿瘤内钙化。结论在骨赘肿瘤中99mTc-MDP的摄取在WBS上为0.6％，通常位于乳腺，肝脏和肺部。核医师在解释WBS时应熟悉这种骨外摄取。SPECT / CT在定位肿瘤内钙化存在的大多数病变方面比单独使用WBS具有更高的准确性。