Identification of Malignant Cells In Serous Effusions Using A Panel of Monoclonal Antibodies Ber-Ep4, Mca-B-12 and Ema

A panel of three monoclonal antibodies (MoAbs) was tested on 29 benign and 53 malignant effusions with the aim of investigating its usefulness for the discrimination between benign and malignant lesions. The panel consisted of MoAbs directed against epithelial membrane antigen (EMA); MCA-b-12, reacting with a 350 kD glycoprotein with mucin-like characteristics present on human breast cancer cells and various other normal and neoplastic tissues, and Ber-EP4, directed against a 34 and 39 kD glycopeptide on human epithelial cells but not on mesothelium. Fifty-two (98%) of the malignant effusions reacted with EMA, 49 (92%) with MCA-b-12 and 44 (83%) with Ber-EP4. Fourteen per cent of benign effusions reacted with EMA, 17% with MCA-b-12 and 7% with Ber-EP4. All seven effusions obtained from patients with a malignant mesothelioma reacted with EMA, six of the seven cases staining intensively. None of the seven stained with Ber-EP4. MCA-b-12 did not react with the cells in one case of malignant mesothelioma. The results suggest that the combination of EMA and Ber-EP4 may be used to discriminate between benign and malignant cells and possibly also between adenocarcinoma and malignant mesothelioma. MCA-b-12 followed in general the reaction pattern of EMA, although often with a less intense staining reaction, making this antibody unsuitable for inclusion in the panel.     

SM047 immunoreactivity in peritoneal fluids

SM047 is a recently developed monoclonal antibody generated against an ovarian adenocarcinoma cell line. A recent immunohistochemical study has shown that SM047 is strongly expressed in tissue sections of most ovarian serous adenocarcinomas. This study aimed to ascertain whether SM047 staining is of value in cytological preparations of peritoneal fluid. A total of 206 consecutive peritoneal fluids were stained immunocytochemically with SM047, CA125, monoclonal carcinoembryonic antigen (mCEA), Ber-EP4 and cytokeratins (CK7 and 20). SM047 positivity was present in reactive mesothelial cells in 117 of 141 (83%) benign cases in which these were present. SM047 positive tumour cells were present in 22 of 23 (96%) ovarian serous adenocarcinomas and in small numbers of gastric adenocarcinomas (two of three), mesotheliomas (one of two) and pancreatic adenocarcinomas (one of one). All six colorectal and two breast adenocarcinomas were negative with SM047. Reactive mesothelial cells in all cases were positive with CK7 and in most cases with CA125. They were negative with CEA, Ber-EP4 and CK20. All adenocarcinomas were positive with Ber-EP4 and mesothelial cells were always negative. All colorectal adenocarcinomas were positive with CK20. This study shows that SM047 staining may be of value in the diagnosis of an ovarian serous adenocarcinoma in peritoneal fluids. Negative staining helps to exclude a primary ovarian serous adenocarcinoma and is characteristic of colorectal adenocarcinoma. The small numbers of other malignancies in the study precludes a judgement of the value of SM047 staining in these neoplasms. SM047 staining may be useful, as part of a larger panel, in the work up of patients with peritoneal effusions.     

Characterizing subpopulations of neoplastic cells in serous effusions. The role of immunocytochemistry

OBJECTIVE: To analyze the role of immunochemistry in serous effusions. STUDY DESIGN: We analyzed cell blocks of 18 pleural and 18 peritoneal effusions diagnosed as malignant (18), benign (14) and suspicious (4). They were immunostained by the avidin-biotin complex method with a panel of four monoclonal antibodies--CEA, Ber-EP4, LeuM1 (CD15) and p53--and, for lectins (Ulex europaeus) UEA-l, ConA and ConBr. RESULTS: Seventeen of the 18 cases of adenocarcinoma were positive for CEA (95%), 12 (66.6%) for Ber-EP4, 11 (61%) for CD15 and 11 (61%) for p53. Twelve of the 18 (66.6%) were positive for UEA-1, CEA, Ber-EP4 and CD15. UEA-1 did not react with mesothelial cells. p53 Gave a positive reaction in only one case, reactive mesothelial cells. ConA and ConBr reacted indiscriminately with benign and malignant cells; thus, it was not useful in distinguishing between these cells. CONCLUSION: In this context no antibody used alone is reliable for corroborating a diagnosis, but the selective use of a small panel of three markers (CEA, Ber-EP4 and LeuM1) can be very useful in solving diagnostic difficulties in the cytodiagnosis of serous effusions.     

Cytopathology of malignant mesothelioma. Reappraisal of the diagnostic value of collagen cores

The identification of malignant mesothelial cells in cytological smears prepared from serous effusions is still hampered by the lack of features specific for mesothelial differentiation. We examined the diagnostic value of collagen cores within clusters of tumour cells in cytological smears prepared from effusions from 43 patients with malignant mesothelioma and of 62 cases of metastatic adenocarcinoma. In Giemsa-stained smears collagen cores were detected in 51% of the cases of malignant mesothelioma and in none of the smears with metastatic adenocarcinoma. Using the Azan stain, collagen cores were detected in 64% of the malignant mesotheliomas and 4% of the adenocarcinomas. Immunoelectron microscopy demonstrated that the collagen cores are largely composed of collagen type III fibrils and some elastin embedded in a homogenous extracellular matrix. It can be concluded that the presence of collagen cores within clusters of tumour cells is highly suggestive of mesothelial differentiation and a common finding in malignant mesothelioma.     

Monoclonal antibodies in the cytodiagnosis of serous effusions

In order to assess the value of immunocytochemical staining as a method of discriminating between benign reactive mesothelial cells and malignant epithelial cells in serous effusions, we have studied the reactions of a panel of commercially available antibodies on cells harvested from 83 pleural and peritoneal fluids and compared the results with the clinical and cytological diagnoses. The antibodies used were raised against cytokeratin (PKK1), epithelial membrane antigen (EMA), carcino-embryonic antigen (CEA), pregnancy specific B1-glycoprotein (SP1) and leucocyte common antigen (LCA). Anti-CEA was positive in 16 of 39 effusions (41%) containing carcinoma cells. Pregnancy specific B1-glycoprotein (SP1) was positive in 33% of the same samples. Mesothelial cells did not stain with these antibodies. Thus anti-CEA and SP1 can be used to discriminate between benign mesothelial and malignant epithelial cells in effusions. Anti-PKK1 stained both benign reactive mesothelial cells and malignant epithelial cells and cannot be used to discriminate between these two cell types. Strong positive staining of malignant cells was noted with anti-EMA. However, as occasional weak staining of mesothelial cells was also noted, strong staining with this antibody may be regarded as suspicious but not conclusive of malignancy.     

Diagnostic utility of GLUT-1 expression in the cytologic evaluation of serous fluids

OBJECTIVE: To evaluate the extent to which adenocarcinomas in body cavity fluids express GLUT-1 in comparison to currently available markers for adenocarcinomas. STUDY DESIGN: Archival paraffin-embedded cell blocks of serous fluids from 25 cases of benign effusions containing reactive mesothelial cells and 39 cases of malignant effusions with metastatic adenocarcinoma (11 ovarian, 11 pulmonary, 9 gastrointestinal and 8 breast) were retrieved from the surgical pathology files. All cases were stained with antibodies for GLUT-1, Ber-Ep4, B72.3 and CEA. Positive staining was defined as distinct linear membrane staining for GLUT-1 and Ber-EP4, cytoplasmic staining for CEA, and cytoplasmic or membrane staining for B72.3. Strong staining in at least 10% of the tumor cells was required in order to consider the case positive for the particular marker. RESULTS: GLUT-1 was expressed in 72% (28 of 39) of cases of malignant effusions: 100% (11 of 11) from the ovary, 91% (10 of 11) from the lung, 67% (6 of 9) from the gastrointestinal tract and 12% (1 of 8) from the breast. None (0 of 25) of the benign effusions expressed GLUT-1. Malignant effusions expressed CEA in 74% (29 of 39), Ber-Ep4 in 85% (33 of 39), and B72.3 in 62% (24 of 39). Benign effusions expressed CEA in 3 cases and B72.3 in 2 cases. CONCLUSION: GLUT-1 is a useful marker that can be applied to cytologic specimens. It can be used as a reliable component of an antibody panel to distinguish reactive mesothelial cells from metastatic adenocarcinoma in particular adenocarcinomas of body cavity effusions, in particular adenocarcinomas of ovarian and pulmonary origin.     

Comparison of Monoclonal Antibodies Aua1 and Ber Ep4 With Anti-Cea For Detecting Carcinoma Cells In Serous Effusions and Distinguishing Them From Mesothelial Cells

Commercially available monoclonal antibodies AUA1, BER EP4 and carcinoembryonic antigen (CEA) were applied to cell blocks from 95 serous effusions. AUA1 and BER EP4 were reactive with 89% of effusions known to contain carcinoma cells, and anti-CEA with 71%. They also reacted with cells in two effusions from patients with malignant disease which were regarded as negative on conventional cytological examination of Papanicolaou-stained smears. They were negative in all but one of the benign effusions. Using all three antibodies, 95% of effusions containing carcinoma cells were detected. Use of these antibodies could improve the cytological diagnosis of serous effusions.     

Diagnostic utility of BCA-225 in detecting adenocarcinoma in serous effusions

OBJECTIVE: To determine the diagnostic value of the BCA-225 antibody in discriminating adenocarcinoma from benign mesothelium in body cavity effusions. STUDY DESIGN: One hundred four cases of unequivocally benign (34 cases) and malignant (70 cases) serous effusions with cell block material were immunostained for BCA-225 using the ABC method without antigen retrieval. The percentage of positively staining cells in each case was estimated in a blind fashion. RESULTS: BCA-225 stained at least 10% of morphologically malignant cells in 28 of 32 (88%) breast carcinomas and 58 of 67 (87%) adenocarcinomas overall. Neuroendocrine carcinomas (two cases) and one mesothelioma were positive in < or = 5% of their respective tumor cells. Of 34 benign cases, 6 (18%) exhibited positive staining, albeit in rare, morphologically benign cells. CONCLUSION: BCA-225 is able to discriminate adenocarcinoma from reactive mesothelium in cell block preparations and may prove useful as part of an antibody panel.     

Immunocytochemistry and DNA-image cytometry in diagnostic effusion cytology. II. Diagnostic accuracy in equivocal smears.

To determine sensitivity and specificity of different antibodies for the immunocytochemical detection of malignant cells in diagnostically equivocal effusions in comparison with those achieved by DNA-image cytometry. 65 cytologically doubtful effusions of the serous cavities were stained with twelve antibodies. Furthermore, DNA-image cytometry was performed. Data were correlated with patient follow-up. Sensitivity of cellular staining of Ber-EP4 for the identification of malignant cells was 77.8%, specificity of absent staining for benign cells was 100%. Positive predictive value for the identification of malignant cells was 100%, negative value 65.5%. Sensitivity of DNA-aneuploidy for the identification of malignancy was 82.9%, specificity of DNA-non-aneuploidy for benignity 94.7%. The positive predictive value of DNA-aneuploidy for the occurrence of malignant cells was 96.7%. Negative predictive value of DNA-non-aneuploidy was 72.0%. Combining immunocytochemistry applying Ber-EP4 only and DNA-cytometry in equivocal effusions resulted in a sensitivity of 88.9% for the identification of malignant cells associated with a 95.0% specificity. Positive predictive value was 97.7%, the negative one 79.2%.     

Utility of HBME-1 immunostaining in serous effusions

Utility of HBME-1 immunostaining in serous effusions
HBME-1 is an anti-mesothelial cell monoclonal antibody derived from human mesothelioma cells. We investigated 227 body cavity effusions to test its utility in differentiating mesothelioma from adenocarcinoma. HBME-1 outlined cell membranes in non-neoplastic mesothelial cells. Thick surface staining was observed on all mesotheliomas. HBME-1 reactivity was also detected in 24% of metastatic carcinomatous effusions. Most ovarian carcinomas (83%) reacted with this antibody, showing surface staining. Cytoplasmic HBME-1 immunoreactivity was observed in a small proportion of non-ovarian adenocarcinomas (14%). Despite its limited specificity, HBME-1 might be added to the battery of other markers of epithelial and/or mesothelial differentiation to be used in cases of suspected mesothelioma. Evaluation of suspicious cells should include careful study of the pattern of immunostaining.     

Malignant ascites of serous papillary ovarian adenocarcinoma. An immunocytochemical study of the tumor cells

In 17 malignant peritoneal effusions due to papillary serous adenocarcinoma of the ovary, the reaction patterns of the tumor cells to monoclonal antibodies (MAbs) against surface antigens were studied and compared with the reaction patterns of mesothelial cells in the same effusions. The following surface markers were used with the adhesive slide method: epithelial membrane antigen (EMA), human epithelium-specific cell surface antigen (HEA-125), human endothelial antigen (BMA-120), carcinoembryonic antigen (CEA 3-13), an antibody against natural killer cells and cytotoxic cells (BMA-070), granulocyte antigen (Leu M1) and leukocyte antigen of class I (HLA-1). In all cases, from 30% to 95% of the tumor cells reacted with EMA and HEA-125. Tumor cells showed a positive staining with CEA 3-13 in only five cases. In all cases, from 75% to 95% of the tumor cells reacted positively with BMA-120. The reactivity of a few mesothelial cells with EMA and of all mesothelial cells with BMA-120 did not interfere with the identification of positive tumor cells since the reaction patterns were different. Interestingly, our study demonstrated that BMA-070, an MAb identifying natural killer cells and cytotoxic cells, is also a most useful tumor marker. The same was found to be true for Leu M1, an MAb originally thought to react only with granulocytes. The tumor cells showed a partial or total loss of the expression of HLA-1 reactivity. Since all cases were immunocytochemically positive for tumor cells while conventional cytology was positive in only 13 of the cases, the immunocytochemical analysis of malignant peritoneal effusions due to papillary serous adenocarcinoma of the ovary seems able to improve the cytologic diagnosis of the fluids.     

Diagnostic Accuracy of Ber-EP4 for Metastatic Adenocarcinoma in Serous Effusions: A Meta-Analysis

Numerous studies have investigated the utility of Ber-EP4 in differentiating metastatic adenocarcinoma (MAC) from malignant epithelial mesothelioma (MM) and/or reactive mesothelial cells (RM) in serous effusions. However, the results remain controversial. The aim of this study is to determine the overall accuracy of Ber-EP4 in serous effusions for MAC through a meta-analysis of published studies. Publications addressing the accuracy of Ber-EP4 in the diagnosis of MAC were selected from the Pubmed, Embase and Cochrane Library. Data from selected studies were pooled to yield summary sensitivity, specificity, positive and negative likelihood ratio (LR), diagnostic odds ratio (DOR), and receiver operating characteristic (SROC) curve. Statistical analysis was performed by Meta-Disc 1.4 and STATA 12.0 softwares. 29 studies, based on 2646 patients, met the inclusion criteria and the summary estimating for Ber-EP4 in the diagnosis of MAC were: sensitivity 0.8 (95% CI: 0.78–0.82), specificity 0.94 (95% CI: 0.93–0.96), positive likelihood ratio (PLR) 12.72 (95% CI: 8.66–18.7), negative likelihood ratio (NLR) 0.18 (95% CI: 0.12–0.26) and diagnostic odds ratio 95.05 (95% CI: 57.26–157.77). The SROC curve indicated that the maximum joint sensitivity and specificity (Q-value) was 0.91; the area under the curve was 0.96. Our findings suggest that BER-EP4 may be a useful diagnostic adjunctive tool for confirming MAC in serous effusions.     

Ultrastructure of pleural mesothelioma and pulmonary adenocarcinoma in malignant effusions as compared with reactive mesothelial cells.

OBJECTIVE: To determine the ultrastructural features of diffuse malignant pleural mesothelioma cells in cytologic specimens from pleural effusions. STUDY DESIGN: We retrospectively studied 35 pleural effusions: 12 diffuse malignant pleural mesotheliomas (8 epithelial type, 4 biphasic type), 12 pulmonary adenocarcinomas and 11 cases of reactive mesothelial cells. RESULTS: In the cytoplasm, reactive and malignant mesothelial cells had more-abundant intermediate filaments (P < .05, P < .01) and fewer free ribosomes (P < .001, P < .001) than adenocarcinoma cells. Reactive mesothelial cells had fewer mitochondria than mesothelioma cells (P < .05). Mesothelioma cells had longer, thinner microvilli on the cell surfaces (P < .001); length/diameter ratios of microvilli were 19.1 +/- 7.0 (mesothelioma) vs. 9.1 +/- 2.2 (adenocarcinoma) and 9.2 +/- 2.4 (mesothelial cells). Giant intercellular junctions (desmosomes or desmosomelike structures > 1 micron in length) were found in eight cases of mesothelioma. Core filaments or rootlets in microvilli were present in two cases of adenocarcinoma. CONCLUSION: Because cytologic specimens from pleural effusions were easy to obtain, we think ultrastructural cytology is useful in distinguishing mesothelioma from adenocarcinoma and benign effusions.     

Immunofluorescent staining of metastatic carcinoma cells in serous fluid with carcinoembryonic antibody, epithelial membrane antibody, AUA-1 and BER-EP4

Using an indirect immunofluorescence technique, we assessed the accuracy and clinical usefulness of a panel of monoclonal and polyclonal antibodies. the panel consisted of carcinoembryonic antibody (CEA) and epithelial membrane antibody (EMA), AUA-1, and Ber-EP4 conjugated with fluorescein isothiocyanate. Twenty-six specimens from pleural, peritoneal or pericardial effusions known to contain carcinoma cells (adenocarcinoma or large cell anaplastic carcinoma) and 16 specimens without carcinoma were first examined. the sensitivity and specificity for each of the antibodies were as follows: CEA, 71% and 75%; EMA, 96% and 81%; AUA-1, 80% and 100%; and Ber-EP4, 85% and 100%, respectively. the panel of antibodies was then applied to a group of 14 'problematic' fluids. These had been identified as causing dilemmas in interpretation, either because the cells in the fluids were of equivocal appearance on light microscopy, or the cytological diagnosis was different from that expected in the light of the clinical condition of the patient. Insufficient cellular material was present in one specimen. In five (39%) of the cases the immunochemical staining supported the light microscopic diagnosis. In four (30%) cases, however, the results indicated that the original light microscopic report was incorrect. Two of these were examples of large cell carcinoma of the lung, in which false negative reports had been issued on pleural fluids. the other two were cases of benign ovarian tumours in which a false positive report had been issued. the immunostaining also clarified the final diagnosis in the three patients (23%) on whom 'suspicious' cytological reports had previously been issued. the remaining case, fluid from a patient with a high grade mixed Mullerian tumour of the ovary, was unresolved. We conclude that immunofluorescent staining by AUA-1, EMA and Ber-EP4 is an aid in the cytological interpretation of serous fluids. CEA is much less helpful.     

Significance of immunocytochemical expression of E-cadherin, N-cadherin and CD44 in serous effusions using liquid-based cytology

OBJECTIVE: To assess the diagnostic utility of E-cadherin (E-cad), N-cadherin (N-cad) and CD44 to discriminate adenocarcinoma cells from benign and malignant mesothelial cells in body cavity fluids and to clarify the origin of cancer cells. STUDY DESIGN: A total of 120 ThinPrep (Cytyc Corp., Boxborough, Massachusetts, U.S.A.) cytologic specimens of serous effusions, which included 22 cases of reactive mesothelium, 6 cases of malignant mesothelioma and 92 cases of metastatic adenocarcinoma from various sites, were immunostained for E-cad, N-cad and CD44. RESULTS: Eighty-three of 92 metastatic adenocarcinomas (90.21%) expressed E-cad, while 1 of 6 malignant mesotheliomas and 1 of 22 cases of reactive mesothelium were positive for E-cad. All 6 cases of mesothelioma expressed N-cad, whereas most cases of metastatic adenocarcinomas were negative. CD44 immunoreactivity was seen in 18 of 22 (81.81%) benign effusions and in 21 of 92 (22.82%) metastatic adenocarcinomas. CONCLUSION: The combination of E-cad, N-cad and CD44 appears to be a useful panel for distinguishing metastatic adenocarcinoma, mesothelioma and reactive mesothelium and also for clarifying the exact histogenetic origin of cancer cells. This is of great importance in a few otherwise-insoluble cases because of differences in tumor treatment and prognosis.     

A new epithelial membrane antigen (Calam 27) as a marker of carcinoma in serous effusions

A new monoclonal antibody (Calam 27) that reacts with a membrane antigen present on cells of epithelial origin, but not on cells of mesothelial origin, was investigated as a means of distinguishing between mesothelial cells and malignant cells in cytologic smears of serous effusions from patients with carcinoma. Immunofluorescence staining of cells in 151 effusions from 109 patients with different diseases showed a good correlation between the cytologic diagnosis on routine preparations and the staining with Calam 27. Calam 27 was also used to study the ploidy and cell cycle kinetics of carcinoma cells versus reactive mesothelial cells and normal cells by flow cytometry; these experiments confirmed that Calam 27 is not reactive with mesothelial cells. In conclusion, Calam 27 staining can help to confirm the cytodiagnoses in cases with carcinomatous effusions.     

Mesothelioma Symposium 11.30–12.30 Tuesday 16 September 2003. Cytopathology of malignant mesothelioma

The diagnosis of malignant mesothelioma on the cytology of serous effusions is a two‐phase process. First is to determine that the effusion is malignant based on morphological features such as a highly cellular fluid with many large three dimensional cell aggregates, and/or the recognition of minor malignant criteria including prominent cell engulfment, uniformly present very prominent nucleoli, or the finding of very large (giant) cells. In cell block sections, strong positive staining with EMA often with cell membrane accentuation provides compelling support for a cytological diagnosis of malignancy. Second is to recognize that the malignant cells have a mesothelial phenotype and do not represent metastatic malignancy (usually adenocarcinoma). Criteria in support of mesothelioma include the lack of a ‘two cell’ population, that is one native (mesothelial) and one foreign (metastatic), cells with abundant dense staining cytoplasm, the presence of ‘windows’ where mesothelioma cells lie in close apposition and intracytoplasmic glycogen presenting either as small peripheral vacuoles on MGG stained smears or large yellow refractile crescents on Papanicolaou stained smears. In addition, mesothliomas often possess connective tissue stromal cores occurring as either well‐formed collagen within papillary aggregates or lying free as pink (MGG) or light green (Pap) amorphous material in the background of the smear or in loose association with mesothelioma cells. Finally small orange staining squamous‐like cells can occasionally be identified and sometimes this may be a very prominent finding and has resulted in the false impression of a squamous cell carcinoma. Almost certainly these cells represent apoptotic tumour cells. The connective tissue mucin hyaluronic acid may be found as a net‐like pattern in the smear background or as large hard‐edged magenta‐stained vacuoles on MGG‐stained smears. Cell block sections provide architectural information and it is usually possible to separate mesothelioma aggregates with their cuboidal cells, central nuclei and abundant dense cytoplasm arranged in solid, papillary or hollow clusters from those of adenocarcinoma with less dense, often foamy cytoplasm, often composed of columnar cells with elongated nuclei. Aggregate form in adenocarcinoma can be variable but true acini are a rare finding. These cell block sections provide an ideal medium for histochemistry (PAS with and without diastase digestion) and immunocytochemistry. By using a panel of antibodies (Calretinin and CK 5/6, BerEp4, CEA, B72.3) it is almost always possible to distinguish mesothelioma from metastatic adenocarcinoma. Calretinin and CK 5/6 positive staining and absent staining with BerEp4, CEA and B72.3 is considered diagnostic of mesothelioma.     

Distribution of silver-stained interphase nucleolar organizer regions as a parameter to distinguish neoplastic from nonneoplastic reactive cells in human effusions

The distribution of interphasic nucleolar organizer regions (NORs) was studied in cytologic preparations of human serous effusions in order to differentiate malignant cells from nonmalignant reactive cells. The study was carried out on 80 cases of metastatic adenocarcinoma, 10 cases of mesothelioma, 10 reactive pleural effusions and 5 peritoneal washings. Visualization of NORs at the light microscopic level was obtained using a silver-staining technique for acidic proteins selectively associated with NORs. The morphologic data were also statistically evaluated by means of an automated image analyzer. The quantity of silver-stained NORs was higher in cancer cells (both mesothelioma and adenocarcinoma) than in reactive mesothelial cells. Moreover, NORs were more irregularly distributed within the nucleoli and were more variably sized in cancer cells than in reactive mesothelial cells.     

Lower proliferation rate in metastatic effusion mesothelial cells than in benign effusions

OBJECTIVE: To determine the proliferation rates of mesothelial cells in metastatic and benign effusions. STUDY DESIGN: Immunohistochemistry was performed on formalin-fixed pellets from 16 malignant and 9 benign clinical effusions. Dual staining with antibodies against Ki-67 (MIB-1) and desmin was applied to all effusions to differentiate between benign mesothelial cells and malignant cells, and the proportions of desmin+/Ki-67+ and desmin+/Ki-67- cells were calculated. RESULTS: In 7 malignant effusions no proliferating mesothelial cells were found, whereas some rate of proliferation could always be demonstrated in mesothelial cells in the benign effusions. Further, the median proportions of proliferating cells, malignant 2% vs. benign 11%, differed significantly. CONCLUSIONS: To our knowledge this finding has not been previously described, and it may have implications for both cytologic diagnosis and the understanding of tumor biology and the interaction between tumor cells and mesothelial cells.     

Immunohistochemical differentiation of malignant mesothelioma, mesothelial hyperplasia and metastatic adenocarcinoma in serous effusions, utilizing staining for carcinoembryonic antigen, keratin and vimentin

The cytologic diagnosis of malignant mesothelioma and its distinction from mesothelial hyperplasia and metastatic adenocarcinoma is consistently difficult; tissue studies utilizing the immunohistochemical profiles of carcinoembryonic antigen (CEA) and keratin have demonstrated a reproducible distinction between these tumors. Mesothelium contains vimentin in addition to keratin, but its characterization is hindered by its poor preservation in formalin fixatives; alcohol fixation is far superior. Alcohol-fixed, Papanicolaou-stained smears of serous fluids from five cases of reactive mesothelium, five metastatic adenocarcinomas and five malignant mesotheliomas were stained with polyclonal CEA, antikeratin monoclonals AE1 and AE3 (combined) and monoclonal vimentin utilizing the peroxidase-antiperoxidase method. The study revealed the excellent preservation of mesothelial vimentin staining in all three groups. The reactive mesothelium and mesothelioma groups were strongly positive for vimentin and keratin whereas the metastatic adenocarcinoma group was only positive for keratin and CEA (except one case). These findings support the results of previous tissue studies, disclosing CEA staining in the metastatic adenocarcinomas, but not in the mesotheliomas, and the inability of keratin staining to distinguish between the two. The findings also emphasize that positive vimentin staining will usually exclude a metastatic adenocarcinoma, but will not distinguish between neoplastic and reactive mesothelial states.