New approaches in the diagnostic procedure of malignant pleural effusions

The content of carcinoembryonic antigen (CEA), carbohydrate antigen 19-9 (Ca 19-9), carbohydrate antigen 15-3 (Ca 15-3) and the expression of LewisY related carbohydrate antigens in benign and malignant pleural effusion were determined. These included 35 malignant pleural effusions: 13 breast cancers, 12 lung cancers (6 squamous cell carcinomas, 5 adenocarcinomas and 1 microcytoma), 2 mesotheliomas, 1 epithelioma, 1 kidney cancer, 1 hepatocarcinoma, 1 colon carcinoma, 3 lymphomas, 1 osteosarcoma and 9 benign pleural effusions. We showed that pleural fluid content of CEA, Ca 19-9 and Ca 15-3 were higher in malignant than in benign effusions. However CEA levels in squamous lung cancers were very high in both serum and pleural fluids whereas its levels were only slightly above the cut-off in breast cancers and in lung adenocarcinomas. Serum and pleural fluid Ca 15-3 values were higher in breast and in lung cancers with the highest values in the patients with breast cancer. Furthermore, the LewisY related carbohydrate antigens, evaluated by the reactivity of the cell extracts to MAb B3, were expressed only in breast cancers. These data suggest that pleural fluid content of CEA, and Ca 15-3 associated with the immunoblotting of cell extracts with MAb B3 appear to be very useful to improve the diagnosis of malignant pleural effusions.     

Diagnostic value of carbohydrate antigens in supernatants and sediments of pleural effusions

A panel of tumour markers including carcinoembryonic antigen (CEA), carbohydrate antigen (Ca)15-3, Ca125 and Ca19-9 were measured in the lysate of sediments and in the supernatants of pleural effusions of patients with benign and malignant disease. The tumour markers were also measured in the serum of the same patients. Of these patients, 32 had benign diseases (12 trasudative effusions associated with cirrhosis and 20 with non-malignant exudates: 12 pleuritis and 8 other inflammations) and 103 had malignant effusions (37 breast cancers, 29 lung cancers, 10 ovary cancers, 6 kidney cancers, 11 mesotheliomas and 10 lymphomas). We showed the highest level of CEA in pleural effusions of lung cancer followed by that in pleural effusions of breast cancer; whereas Ca15-3 was very high in the pleural effusions of breast and lung cancer. Concerning the lysate of sediment, CEA was high in the pleural effusions of patients with lung cancer and Ca15-3 in those of patients with breast cancer. The other markers are much less useful. For the remaining tumours, none of the markers tested appear to aid in the diagnosis of disease. In conclusion, our data suggest that the combined determination of tumour markers on supernatants and sediments of pleural effusion may provide additional information on the nature of pleural effusion, especially for cases with negative cytology.     

Matrix metalloproteinase-2 and -9 in the sera and in the urine of human oncocytoma and renal cell carcinoma

Matrix metalloproteinases (MMPs) are a family of zinc-dependent endopeptidases, capable of degrading all the molecular components of extracellular matrix. MMPs have been shown to play critical roles in tumor cell invasion and metastasis. We verified the activity of MMPs in the sera and in the urine of patients with kidney carcinoma by gelatin zymography. Of these patients, 16 had clear cell renal carcinoma (ccRCC) and 4 patients had oncocytoma. The sera and the urine of 16 healthy subjects were used as controls. In the sera, zymography analysis showed gelatinolytic bands at 72?kDa (gelatinase?A) at 92, 130 and 240?kDa (gelatinase?B). MMP-9 activity was slightly enhanced in sera from ccRCC compared with oncocytoma patients. Serum MMP-2 activity was similar in ccRCC and in oncocytoma patients. In the urine, 2 oncocytoma patients and 3 (33%) of the ccRCC patients showed gelatinolytic activity, whereas MMPs could not be detected in the concentrated urine of healthy subjects. The most abundant lytic activity was at 92?kDa, whereas MMP-2 was present in lesser quantities. However, there was broad overlap of the data and we did not find any correlation to type, stage or grade. Therefore, despite previous evidence, MMP-2 and -9 activity in serum and urine may not be useful biomarker for kidney carcinomas.     

Diagnostic value of CEA, CA 15-3, CA 19-9, CYFRA 21-1, NSE and TSA assay in pleural effusions

The aim of this study was to evaluate the individual and combined diagnostic utility of six tumor markers in patients with pleural effusion. Pleural and serum levels of carcinoembryonic antigen (CEA), carbohydrate antigen 15-3 (CA 15-3), carbohydrate antigen 19-9 (CA 19-9), cytokeratin fragment 19 (CYFRA 21-1), neuron-specific enolase (NSE) and total sialic acid (TSA) were assayed in 74 patients with pleural effusions (44 malignant and 30 benign). All tumor markers except TSA and NSE were increased in both serum and pleural fluid of patients with malignant diseases. Using the cut-off values 3 ng/ml, 14 U/ml, 5 U/ml, 8 ng/ml and 70 mg/dl for pleural fluid CEA, CA 15-3, CA 19-9, CYFRA 21-1 and TSA, respectively, the sensitivity (%) and specificity (%) of these tumor markers were as follows: CEA; 52/77, CA 15-3; 80/93, CA 19-9; 36/83, CYFRA 21-1; 91/90, TSA; 80/67, for differentiating malignant effusions from benign. When CA 15-3 and CYFRA 21-1 combined, the sensitivity and specificity were increased (100 and 83%, respectively). Classifying the malignant effusions as bronchial carcinoma and malignant pleural mesothelioma, CEA was shown to have the highest sensitivity and specificity (88 and 90%, respectively) while the combination of CEA with other tumor markers increased sensitivity but decreased specificity. According to our results, tumor markers are not suitable for the differential diagnosis of malignancy.     

Evaluation of seven tumour markers in pleural fluid for the diagnosis of malignant effusions

Carcinoembryonic antigen (CEA), carbohydrate antigens 15-3, 19-9 and 72-4 (CA 15-3, CA 19-9 and CA 72-4), cytokeratin 19 fragments (CYFRA 21-1), neuron-specific enolase (NSE) and squamous cell carcinoma antigen (SCC) were evaluated in pleural fluid for the diagnosis of malignant effusions. With a specificity of 99%, determined in a series of 121 benign effusions, the best individual diagnostic sensitivities in the whole series of 215 malignant effusions or in the subgroup of adenocarcinomas were observed with CEA, CA 15-3 and CA 72-4. As expected, a high sensitivity was obtained with SCC in squamous cell carcinomas and with NSE in small-cell lung carcinomas. CYFRA and/or CA 15-3 were frequently increased in mesotheliomas. Discriminant analysis showed that the optimal combination for diagnosis of non-lymphomatous malignant effusions was CEA + CA 15-3 + CYFRA + NSE: sensitivity of 94.4% with an overall specificity of 95%. In malignant effusions with a negative cytology, 83.9% were diagnosed using this association. The association CYFRA + NSE + SCC was able to discriminate adenocarcinomas from small-cell lung cancers. Regarding their sensitivity and their complementarity, CEA, CA 15-3, CYFRA 21-1, NSE and SCC appear to be very useful to improve the diagnosis of malignant pleural effusions.     

Elevated levels of angiostatin in effusions from patients with malignant disease

The aim of this study was to determine the presence of angiostatin in ascitic and pleural effusions from cancer patients, as well as of metalloproteinases (MMPs) and urokinase-type plasminogen activator (uPA), both involved in angiostatin generation in in vitro models. Ascitic fluids, pleural exudates, and sera from 21 cancer patients were analyzed for the presence of angiostatin by western blot, whereas gelatinases MMP-2 and MMP-9, and uPA were evaluated by zymography. Our study revealed elevated levels of angiostatin in effusions of cancer patients, contrasting with mostly intermediate levels in less than half of their sera, and undetectable levels in normal sera. Despite the observation of enhanced levels of HMW-uPA and MMP-2 in malignant effusions from cancer patients, their analysis in individual samples showed no association between angiostatin presence and the enzymes, suggesting that the latter would not play an unimportant role, if any, in in vivo generation of angiostatin.     

肿瘤标志物联合检测在良恶性胸腔积液鉴别诊断中的价值

 目的　探讨胸腔积液4种肿瘤标志物联合检测在良恶性胸腔积液鉴别诊断中的价值。方法　采用电化学发光免疫法检测126例胸腔积液患者（其中恶性组52例,良性组74例）癌胚抗原（CEA）、糖类抗原125（CA125）、糖类抗原15-3（CA15-3）和细胞角蛋白片段19（CYFRA21-1）水平, 并计算上述指标单独和与CEA联合检测在诊断中的敏感度、特异度、准确度和约登指数（YI）。结果　恶性组4种肿瘤标志物水平均明显高于良性组（P＜0.01）。单项检测各种肿瘤标志物的敏感度以CA125最高（90.4 %）,特异度以CYFRA21-1最高（79.7 %）,诊断准确度以CEA和CYFRA21-1最高（71.4 %）,YI以CEA最高（0.41）。联合检测较单项检测敏感度、准确度和YI明显提高,其中CEA、CYFRA21-1和CA15-3三项联合效果最好,敏感度为92.3 %,特异度为78.4 %,准确度为84.1 %,YI值最高为0.71。四项联合敏感度为94.2 %,特异度为75.7 %,准确度为83.3 %,YI值为0.70,与三项联合结果相比差异无统计学意义（P＞0.05）。结论　单项检测的诊断价值有限,CEA、CYFRA21-1和CA15-3三项联合效果最好、最经济,可指导患者恰当选择进一步的侵入性检查手段。     

Increased expression and activation of gelatinolytic matrix metalloproteinases is associated with the progression and recurrence of human cervical cancer

Cancer-derived matrix metalloproteinases (MMPs) are proposed to be essential for tumor stromal invasion and subsequent metastasis. To explore the role of MMPs in cancer progression, we examined the expression of various MMPs and tissue inhibitors of MMPs in precancerous and cancerous lesions of the uterine cervix. Immunohistochemical studies demonstrated that MMP-2 and MMP-9 were expressed in >90% of squamous cell carcinomas (SCC) and 83-100% of high-grade squamous intraepithelial lesions (HSIL), but were less frequently expressed in low-grade squamous intraepithelial lesions and normal squamous epithelium (13%). MMP-1, MMP-14, and MMP-15 were detected in 55-81% of SCC cases, and MMP-1 was detected in 39% of HSIL. The tissue inhibitors of MMPs were weakly expressed in SCC (10-61%). By direct analysis of enzyme activities in microdissected specimens, we found that the gelatinolytic activity of MMP-9 was significantly higher in HSIL and SCC than in normal cervix (P < 0.01). The levels of active-form MMP-2 increased progressively from HSIL to SCC of stage I and more advanced stages (P < 0.01). The gelatinolytic activity of MMP-9 and active-form MMP-2 in SCC were strongly correlated with lymphovascular permeation and subsequent lymph node metastasis (P < 0.02). Moreover, the gelatinolytic activity and immunoreactive percentage of both MMP-2 and MMP-9 were significantly higher in SCC cases who had a recurrence than in those who remained free of disease (P < 0.001). Thus, our data demonstrate progressively up-regulated expression of MMP-2 and MMP-9 with SCC progression, and significant associations among their gelatinolytic activity and stage, nodal metastasis, and recurrence.     

Production of matrix metalloproteinase-9 in early stage B-CLL: suppression by interferons.

Besides vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF), matrix metalloproteinases (MMPs) play critical roles in angiogenesis, tumor invasion and metastasis. Increased angiogenesis is observed in chronic B lymphocytic leukemia (B-CLL) and published data reported VEGF and bFGF production in this disease. The purpose of this study was to investigate MMP expression in early stage B-CLL. Elevated MMP-9 concentrations were detected by ELISA in the sera of B-CLL patients (median level 250 ng/ml) compared with healthy donors (67 ng/ml) (P < 0.0001), and immunostaining with antibodies against MMP-9 and B cell antigens (CD19, CD23) substantiated the presence of MMP-9 in tumoral B lymphocytes. By using RT-PCR, ELISA and zymography experiments, we confirmed that B-CLL cells expressed and released the pro-form of MMP-9 with Mr 92 kDa (158-1300 pg/ml/10(6) cells/48 h), p-aminophenylmercuric acetate generating a 82 kDa active form. In contrast, the production of MMP-9 by normal counterpart B cells was significantly low (28-169 pg/ml/10(6)cells/48 h). Moreover, B-CLL culture supernatants contained bFGF (median levels 17 pg/ml/10(6) cells/48 h), VEGF (1.4 pg/ml/10(6) cells/48 h) and TNF-alpha (0.2 pg/ml/10(6) cells/48 h). TNF-alpha and VEGF antibodies blocked MMP-9 at the mRNA and protein levels. Interferons (IFNs) type I or type II repressed MMP-9 gelatinolytic activity in a dose and time dependency, and this was reflected by a parallel inhibition of MMP-9 mRNA and protein. IFNs however did not affect the production of bFGF, VEGF and TNF-alpha. Together, our data show that B-CLL lymphocytes synthesize MMP-9 and emphasize the specific inhibitory actions of IFNs on its expression.     

Diagnostic value of tumor markers for differentiating malignant and benign pleural effusions of Iranian patients

In order to evaluate the diagnostic yield of tumor markers in differentiating malignant and benign pleural effusions, we carried out a prospective study in a group of Iranian people. Pleural and serum levels of carcinoembryonic antigen (CEA), carbohydrate antigen 15-3 (CA15-3), neuron-specific enolase (NSE) and cancer antigen 125 (CA 125) were assayed prospectively in patients with pleural effusion (40 malignant and 37 benign). The highest sensitivity was obtained with a combination of CA 15-3 in serum, and CA 15-3 and CEA in pleural fluid (80%), also with combination of CA 15-3 in serum, and CA 15-3, NSE and CEA in pleural fluid (80%). The highest specificity was obtained with combination of CA 15-3 in serum, and CA 15-3 and NSE in pleural fluid (100%), and also with combination of CA 15-3 in serum, and CA 15-3, NSE and CEA in pleural fluid (100%).     

Detection of Soluble Tumor-associated Antigens in Sera and Effusions Using Novel Monoclonal Antibodies, KL-3 and KL-6, against Lung Adenocarcinoma

Two novel monoclonal antibodies, KL-3 (IgM) and KL-6 (IgG¹),which can detect soluble antigens in sera and effusions (molecularweights > 1,000 K) were produced against human pulmonaryadenocarcinoma VMRC-LCR cells. KL-3 and KL-6 antibodies reactedwith asialo- and sialo-carbohydrate antigenic determinants,respectively. Both carbohydrate epitopes appear, from competitiveinhibition studies, to be different from Le^x, Le^y, sialyl Le^aand sialyl Le^xi which were recognized with FH2, AH6, NS19-9and FH6 antibodies, respectively. Using an enzyme linked immunosorbentassay, elevated KL-6 antigen levels were frequently observedin the sera of patients with lung adenocarcinoma [52% (17/33)],pancreatic cancer [44% (4/9)] and breast cancer [40% (8/20)],but infrequently in the sera of patients with lung squamouscell carcinoma [18% (4/22)], lung small cell carcinoma [8% (1/13)],gastric cancer [0% (0/19)], colorectal cancer [0% (0/8)] andhepatocellular cancer [13% (1/8)]. The levels and positive ratesof scrum KL-6 antigen increased with the progression of clinicalstage of lung adenocarcinoma. In pleural effusions, the prevalencesof lung adenocarcinoma cases with elevated levels of KL-3 andKL-6 antigens were 76% (13/17) and 82% (14/17), respectively.These monoclonal antibodies can define novel soluble antigensin sera and effusions which could be useful in tumor diagnosesand for monitoring tumor progression.     

Gelatinolytic activity of matrix metalloproteinase-2 and -9 in oesophageal carcinoma; a study using in situ zymography

In this study, we investigated the activity of matrix metalloproteinase (MMP)-2 and -9 by gelatine zymography, immunostaining and in situ gelatine zymography in 30 oesophageal squamous-cell carcinomas. The gelatinolytic activity in situ was detected in all cases with different patterns of localisation. Significant gelatinolysis by stromal cells adjacent to tumour nests was found in 12 cases. Strong gelatinolytic activity appeared within the tumour nest itself in 13 cases. In the other 5 cases, both stromal cells and tumour cells showed the gelatinolytic activity. Gelatine zymography demonstrated a correlation between vascular invasion and activation of MMP-9. It also demonstrated a correlation between lymph node metastasis, lymphatic or vascular invasion and activation of MMP-2. These results suggest that MMPs play an important role in the invasion of oesophageal carcinoma.     

Elevated serum CA 125 levels in patients with benign ascitic or pleural effusions

The tumor-associated antigen CA 125 is widely used in monitoring of ovarian carcinomas. As this determinant is also expressed in proliferating mesothelia, we studied CA 125 levels in serum and effusion fluid of patients with ascitic and pleural effusions. Patients with benign and malignant disease were included. There was no statistically significant or diagnostically useful difference between 26 benign and 44 malignant cases in the CA 125 levels in effusions or sera. In 77% of benign cases, serum levels exceeding 105 U/ml (3 times the recommended upper limit of normal values) were found. Thus, in patients with serous effusions, elevated serum CA 125 values alone do not provide evidence for the presence of an (ovarian) malignancy, but may also indicate a proliferation of mesothelium due to benign disease.     

六种肿瘤标志物在肺癌胸腔积液中的诊断价值

目的通过对胸腔积液和血清中6种肿瘤标志物的检测及胸腔积液脱落细胞学检查,探讨各指标在肺癌胸腔积液中的诊断价值。方法应用化学发光法和酶联免疫分析法测定50例肺癌和30例肺良性疾病患者的胸腔积液和血清中的癌胚抗原（CEA）、糖类抗原19—9（CA19—9）、鳞状细胞癌抗原（SCC）、神经元特异性烯醇化酶（NSE）、细胞角蛋白19片段（CYFRA21—1）、胃泌素前体释放肽（ProGRP）水平,同时对胸腔积液标本进行脱落细胞学检查,并根据受试者工作特性曲线（ROC）建立合理的临床判断临界值。结果肺癌患者胸腔积液中6种肿瘤标志物水平均高于肺良性疾病者,其中CEA、CA19-9、CYFRA21—1、ProGRP水平显著高于肺良性疾病组（P〈0．05）。胸腔积液CEA、血清CYFRA21—1及CEA含量在胸腔积液与血清中的比值（P／S）在各组中的ROC曲线下面积最大。结论胸腔积液CEA、血清CYFRA21—1及CEA的P／S值在鉴别良、恶性胸腔积液中有一定的辅助诊断价值,胸腔积液CEA的诊断价值最大。     

Matrix metalloproteinase-2 and -9 activities correlate with the disease-free survival of oral squamous cell carcinoma patients.

The aim of the present study was to determine whether matrix metalloproteinase (MMP) activities are associated with the clinicopathological features of oral squamous cell carcinomas (OSCCs). Forty-four samples of primary OSCCs were microdissected, incubated in serum-free cell culture medium for 16 h, and the activity of secreted MMPs analyzed by gelatin zymography and densitometry. Two major enzymes with gelatinolytic activity were produced by all tumor samples and characterized as MMP-2 and -9 by their molecular weight, immunoprecipitation using monoclonal antibodies, and specific inhibition by 1,10-phenanthroline or EDTA. Patients with tumors showing elevated activity of MMP-2 and -9 had shorter disease-free survival after treatment than patients with tumors exhibiting low MMP activities. These results suggest that the zymographic measurement of the MMP-2 and -9 activities in OSCC specimens may be useful to predict the disease-free survival period of patients affected by these tumors.     

Evaluation of pleural CYFRA 21-1 and carcinoembryonic antigen in the diagnosis of malignant pleural effusions.

CYFRA 21-1 assay, measuring cytokeratin 19 fragments, was compared with carcinoembryonic antigen (CEA) assay, as an addition to cytological analysis for the diagnosis of malignant effusions. Both markers were determined with commercial enzyme immunoassays in pleural fluid from 196 patients. Cytological analysis and/or pleural biopsy confirmed the malignant origin of the effusion in 99 patients (76 carcinomas, nine pleural mesotheliomas and 14 non-epithelial malignancies). Effusions were confirmed as benign in 97 patients (33 cardiac failures, 39 infectious diseases--including 12 tuberculosis-- and 25 miscellaneous effusions). Both markers were significantly higher in malignant than in benign effusions. All the patients with non-epithelial malignancies presented CYFRA and CEA values lower than the 95% diagnostic specificity thresholds (100 and 6 ng ml(-1) respectively). The diagnostic sensitivity in the group of carcinomas and mesotheliomas was similar for CYFRA (58.8%) and CEA (64.7%). However, CEA had a significantly higher sensitivity in carcinomas (72.4% vs 55.3%), while CYFRA had a clearly higher sensitivity in mesotheliomas (89.9% vs 0%). Interestingly, 12 out of the 16 malignant effusions with a negative cytology were CEA and/or CYFRA positive. Regarding their high diagnostic sensitivity and their complementarity, CEA and CYFRA appear to be very useful for the diagnosis of malignant pleural effusions when cytology is negative.     

糖类抗原125、糖类抗原15-3、糖类抗原19-9和人附睾蛋白4单独及联合检测对卵巢癌的诊断价值

目的研究糖类抗原125(CA125)、CA15-3、CA19-9和人附睾蛋白4(HE4)单独及联合检测对卵巢癌的诊断价值,探讨最优的联合诊断方案。方法选取90例卵巢癌患者、90例良性卵巢疾病患者及90同期健康体检者,分别作为肿瘤组、良性组和健康组。比较3组受试者血清CA125、CA15-3、CA19-9和HE4水平及阳性率,比较上述四种肿瘤标志物单独及联合检测对卵巢癌的诊断灵敏度、特异度及准确度。结果肿瘤组患者CA125、CA15-3、CA19-9和HE4水平及阳性率均高于良性组患者和健康组受试者,良性组患者血清CA125、CA15-3和CA19-9水平均高于健康组受试者,良性组患者血清CA125、CA15-3、CA19-9和HE4阳性率均高于健康组受试者,差异均有统计学意义(P﹤0.05)。CA125+CA15-3+HE4、CA125+CA15-3+CA19-9+HE4诊断卵巢癌灵敏度最高,均为91.11%。HE4单独诊断卵巢癌的特异度最高,为94.44%。CA125+CA15-3+HE4诊断卵巢癌的准确度最高,为85.93%。结论CA125+CA15-3+HE4三项联合检测可提高卵巢癌诊断效率,对临床诊断卵巢癌有参考价值。     

Diagnostic value of CYFRA 21-1, CEA, CA 19-9, CA 15-3, and CA 125 assays in pleural effusions: analysis of 116 cases and review of the literature

Levels of tumor markers in pleural effusions may help to establish the diagnosis of pleural malignancy, but the precise diagnostic value of each marker remains unclear. The aim of this study was to assess the diagnostic value of five common pleural fluid tumor markers, carcinoembryonic antigen (CEA), cytokeratin fragment (CYFRA) 21-1, cancer antigen (CA) 15-3, CA 19-9, and CA 125, and to review the literature from the past 15 years. Pleural fluid samples were collected prospectively from 116 patients and assayed for CEA, CYFRA 21-1, CA 15-3, CA 19-9, and CA 125 levels. A MEDLINE search of the English-language literature from the past 15 years was also done. Effusions were classified as benign or malignant on the basis of their definitive pathologic or cytologic diagnoses. The levels of all pleural tumor markers were statistically significantly higher in the malignant group than in the benign group. The marker with the highest accuracy was CEA (85.3%); CA 15-3, CYFRA 21-1, and CA 19-9 had similar accuracies (75.2%, 72.4%, and 71.5%, respectively), and CA 125 had the lowest accuracy (40.5%). On univariate analysis, tumor-marker combinations did not result in a greater accuracy than that of CEA alone. On multivariate logistic regression, CA 15-3 and CYFRA 21-1 were significant predictors of malignancy. Among the nine reports in the literature comparing 11 different tumor markers, CEA, CA 15-3, and CYFRA 21-1 yielded the best results. We conclude that pleural fluid analysis should include CEA for the diagnosis of malignancy. CA 15-3 and CYFRA 21-1 may serve as alternative options.     

Elevation of sialyl stage-specific mouse embryonic antigen levels in pleural effusion in patients with adenocarcinoma of the lung

Sialyl stage-specific mouse embryonic antigen (SSEA-1) levels were measured in pleural effusions obtained from patients with lung cancer and benign pulmonary disease, using a solid-phase immunoradiometric sandwich assay. The mean (+/- SEM) levels (unit/ml) of pleural fluid sialyl SSEA-1 were 3620 +/- 1419 in adenocarcinoma (n = 25), 123 +/- 30 in nonadenocarcinoma (n = 13) and 95 +/- 19 in benign pulmonary disease (n = 13), respectively. The positive rate was 64% in adenocarcinoma, 7.7% in nonadenocarcinoma, and 0% in benign pulmonary disease, respectively, when a cutoff level was defined as the mean + 3 SD value (300 unit/ml) based on pleural fluid sialyl SSEA-1 levels in benign pulmonary disease. There was a significant positive correlation between pleural fluid levels of sialyl SSEA-1 and those of carcinoembryonic antigen in adenocarcinoma patients (r = 0.8246, P less than 0.01). Pleural fluid sialyl SSEA-1 levels correlated with cytologic findings in adenocarcinoma patients. These observations suggest that sialyl SSEA-1 in pleural effusion is a useful marker to discriminate malignant from nonmalignant and adenocarcinoma from nonadenocarcinoma of the lung.