Cole Laurence A, Khanlian Sarah A, Muller Carolyn Y, Giddings Almareena, Kohorn Ernest, Berkowitz Ross
USA hCG Reference Service, Department of Obstetrics and Gynecology, University of New Mexico, Albuquerque, NM 87131, USA.
Gynecol Oncol. 2006 Aug;102(2):160-4. doi: 10.1016/j.ygyno.2005.12.046. Epub 2006 May 2.
Placental site trophoblastic tumor (PSTT) commonly presents with low and variable concentration of hCG immunoreactivity in serum which can be difficult to differentiate from early stage choriocarcinoma/gestational trophoblastic neoplasm (GTN) or quiescent gestational trophoblastic disease (quiescent GTD). Nontrophoblastic malignancies such as germ cell tumors or other tumors secreting low hCG must also be considered in the differential diagnosis. Because treatments for these conditions are different, a means of differentiating PSTT from other diagnoses is important. We investigate the usefulness of hCG-free beta-subunit to make this discrimination.
Data collected on cases referred to the USA hCG Reference Service for consultation served as a basis for this retrospective analysis. There were 13 cases with histology proven PSTT and 12 with nontrophoblastic malignancy. hCG-free beta-subunit was measured by immunoassay and reported as a proportion of total hCG (hCG-free beta-subunit(%)). hCG-free beta-subunit(%) results were determined for all histologically proven cases of PSTT and for the nontrophoblastic malignancies. Comparisons of hCG-free beta-subunit(%) were made and compared with those of the 82 choriocarcinoma/GTN cases and 69 quiescent GTD cases. The accuracy of hCG-free beta-subunit(%) to discriminate these malignancies was analyzed by investigating the areas under receiver-operating characteristics curve +/- standard error.
hCG-free beta-subunit(%) was the predominant hCG form in cases of PSTT (mean +/- standard deviation, 60 +/- 19%) and nontrophoblastic malignancies (91 +/- 11%), thus discriminating these diagnoses from choriocarcinoma/GTN (9.3 +/- 9.2%) and from quiescent GTD (5.4 +/- 7.8%). The cutoff of >35% free beta-subunit is proposed. At this cutoff, 100% detection at 0% false-positive is achieved. The accuracy of hCG-free beta-subunit(%) for this discrimination is 100 +/- 0%. At a proposed cutoff of >80%, the free beta-subunit test will also distinguish PSTT from nontrophoblastic malignancy, with 77% detection at 23% false-positive or an accuracy of 92 +/- 3.2%.
Measurement of the proportion hCG-free beta-subunit(%) was found to be useful in the diagnosis of PSTT using proposed cutoff values of >35% and >80%. While this finding needs to be confirmed by larger studies, it would be reasonable to measure hCG-free beta-subunit(%) whenever the diagnosis of PSTT is considered.
胎盘部位滋养细胞肿瘤（PSTT）通常表现为血清中人绒毛膜促性腺激素（hCG）免疫反应性浓度低且变化不定，这可能难以与早期绒毛膜癌/妊娠滋养细胞肿瘤（GTN）或静止期妊娠滋养细胞疾病（静止期GTD）相鉴别。在鉴别诊断中还必须考虑非滋养细胞恶性肿瘤，如生殖细胞肿瘤或其他分泌低水平hCG的肿瘤。由于这些疾病的治疗方法不同，因此区分PSTT与其他诊断的方法很重要。我们研究了无hCG的β亚基在进行这种鉴别诊断中的作用。
收集提交给美国hCG参考服务中心进行咨询的病例数据，作为这项回顾性分析的基础。有13例经组织学证实为PSTT的病例和12例非滋养细胞恶性肿瘤病例。通过免疫测定法测量无hCG的β亚基，并报告为总hCG的比例（无hCG的β亚基（%））。确定了所有经组织学证实的PSTT病例和非滋养细胞恶性肿瘤病例的无hCG的β亚基（%）结果。对无hCG的β亚基（%）进行比较，并与82例绒毛膜癌/GTN病例和69例静止期GTD病例的结果进行比较。通过研究受试者工作特征曲线下的面积±标准误差，分析无hCG的β亚基（%）鉴别这些恶性肿瘤的准确性。
无hCG的β亚基（%）是PSTT病例（平均±标准差，60±19%）和非滋养细胞恶性肿瘤（91±11%）中hCG的主要形式，从而将这些诊断与绒毛膜癌/GTN（9.3±9.2%）和静止期GTD（5.4±7.8%）区分开来。建议游离β亚基>35%的临界值。在此临界值下，可实现100%的检测率且假阳性率为0%。无hCG的β亚基（%）用于这种鉴别诊断的准确性为100±0%。在建议的临界值>80%时，游离β亚基检测也可将PSTT与非滋养细胞恶性肿瘤区分开来，检测率为77%，假阳性率为23%，或准确性为92±3.2%。
发现测量无hCG的β亚基（%）比例，采用建议的>35%和>80%的临界值，对PSTT的诊断有用。虽然这一发现需要通过更大规模的研究来证实，但在考虑诊断PSTT时，测量无hCG的β亚基（%）是合理的。
