Challenges in the interpretation peritoneal cytologic specimens.
Abstract: Context. -- The presence of malignant cells in peritoneal washings leads to classification as International Federation of Gynecology and Obstetrics stage IC or higher in ovarian carcinomas and at least International Federa Gynecology and Obstetrics stage IIIA in endometrial carcinomas. Unfortunately, the morphologic examination of cytologic specimens has not proven to be a sensitive or specific diagnostic tool. Malignant cells might be few in number and might be unrecognized among a large population of mesothelial cells and/or macrophages, or reactive mesothelial cells might be misinterpreted as neoplastic cells leading to unnecessary chemotherapy.

Objective. -- To evaluate the main pitfalls in the evaluation of peritoneal washings in patients with gynecologic malignancies and analyze the ancillary studies that might be helpful to achieve the correct diagnosis with an emphasis on immunocytochemistry.

Data Sources. -- A comprehensive review of the literature was performed.

Conclusions. -- Peritoneal effusions may represent major challenges to the pathologist and can have important clinical implications. Immunostains for epithelial markers such as B72.3, MOC-31, and Ber-EP4 represent the best available markers to identify epithelial cells. Caution is advised to not overdiagnose endometriosis or endosalpingiosis as adenocarcinoma.
Article Type: Report
Subject: Diagnosis (Methods)
Gynecology (Methods)
Ovarian cancer (Diagnosis)
Cytology (Usage)
Tumor staging (Methods)
Biological markers (Usage)
Biopsy (Usage)
Author: Lin, Oscar
Pub Date: 05/01/2009
Publication: Name: Archives of Pathology & Laboratory Medicine Publisher: College of American Pathologists Audience: Academic; Professional Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2009 College of American Pathologists ISSN: 1543-2165
Issue: Date: May, 2009 Source Volume: 133 Source Issue: 5
Product: Product Code: 8521214 Cellular Biology NAICS Code: 54171 Research and Development in the Physical, Engineering, and Life Sciences
Accession Number: 230151995
Full Text: Peritoneal washing cytology has been used in the evaluation of gynecologic malignancies since the early 1950s. The International Federation of Gynecology and Obstetrics (FIGO) introduced peritoneal washing as part of the staging of ovarian carcinomas in 1975. For ovarian carcinomas, the presence of malignant cells in peritoneal washings is important for substaging patients with disease that is apparently organ-confined (FIGO stage I) and for the detection of recurrent carcinoma. Tumor confined to an ovary is considered FIGO stage IA, whereas ovarian carcinomas involving the ovarian surface and/or detectable in a peritoneal washing specimen is assigned FIGO stage IC. A 5-year survival rate of 90% in patients with stage IA, grade I ovarian carcinomas contrasts with 68% and 56% in patients with stage I lesions showing ovarian excrescences or ovarian capsular rupture, respectively. Similar results were found in second-look laparotomy patients. (1) Survivals in patients with ovarian carcinoma have also been reported to differ significantly, based on peritoneal cytology, regardless of disease stage. The progression-free interval and survival rate are reportedly influenced significantly by tumor grade and the presence of microscopic tumor identified on the basis of biopsy or cytology. (2-6)

The presence of malignant cells in peritoneal washings from patients with endometrial carcinoma assigns the tumor to FIGO stage IIIA or higher. Most studies suggest that cytology is a predictor of poor outcome, (3, 7, 8) but the clinical significance of positive peritoneal washings in patients with non-myometrial invasive, FIGO grade I endometrioid adenocarcinoma is debatable. (8) The presence of malignant cells in washings is also an independent, negative prognostic factor in patients with advanced-stage disease. These patients have a reported recurrence rate of 23%, which is similar to that of patients with occult lymph node metastasis identified through surgical staging. Currently, patients with cytologically defined stage IIIA endometrial cancer are included among patients with advanced-stage disease, (9) but this may be reassessed in an upcoming revision of the guidelines for FIGO staging of endometrial carcinoma.

As stated previously, the presence of malignant cells in serous effusions signifies spread of disease beyond the organ of origin and is associated with significant therapeutic and prognostic implications. Unfortunately, the morphologic examination of cytologic specimens has not proven to be a sensitive or specific diagnostic tool. The malignant cells might be few in number and might be unrecognized among a large population of mesothelial cells and/or macrophages. Mesothelial cells, on the other hand, might show reactive changes due to a wide variety of stimuli. These changes consist of marked nuclear enlargement, hyperchromasia, and cytoplasmic alterations, which can be misinterpreted as malignant cells. (10-12) Also, postradiation changes may lead to cellular changes that can mimic a malignancy. Additionally, benign conditions such as endosalpingiosis may be extremely difficult to differentiate from borderline ovarian tumors (tumors of low malignant potential) or low-grade serous carcinomas in cytologic specimens. Consequently, the false-positive rate of cytology in the evaluation of serous effusions has been reported to be as high as 4.5%. The main reason for a false-positive diagnosis is the misinterpretation of reactive mesothelial cells as malignant epithelial cells. Other potential pitfalls include the presence of psammoma bodies, endometriosis, and endosalpingiosis. (4, 13-15) The false-negative rate for cytology in serous effusions is believed to be approximately 20%. Factors that contribute to this relatively high falsenegative rate include poor distribution of peritoneal washings, infrequent exfoliation of malignant cells, and interpretive errors. As a positive peritoneal washing diagnosis leads to treatment with chemotherapy in many instances, diagnostic accuracy is essential.


Serous carcinoma usually presents as cellular specimens containing single cells or poorly cohesive irregular cell clusters with large, pleomorphic nuclei and prominent nucleoli. Peritoneal washings involved by endometrioid carcinomas display loose, 3-dimensional clusters of cells with eccentric, pleomorphic nuclei and abundant delicate cytoplasm, coarse chromatin pattern, and prominent nucleoli. Clear cell carcinoma also demonstrates similar cytologic features.

The main differential diagnosis of adenocarcinoma in a peritoneal washing is reactive mesothelial cells, but endosalpingiosis and endometriosis also frequently contribute to diagnostic difficulties. Reactive mesothelial cells usually present as clusters of epithelioid cells with occasional cell ball or papillary cluster formation. The reactive mesothelial cells show cellular enlargement, dense cytoplasm and large nuclei with increased nuclear to cytoplasmic ratio. Occasionally the cells might be vacuolated or contain prominent nucleoli. The presence of cellular "windows" might help to identify the cells as mesothelial. Cells from fallopian tubes in pelvic washings may also lead to false-positive diagnosis. They are usually present as a few small fragments of ciliated columnar epithelium in flat sheets. Endosalpingiosis might be nearly impossible to distinguish from well-differentiated serous neoplasms such as serous borderline tumor and low-grade serous carcinoma. Cases of endosalpingiosis display organized, tight clusters with occasional nonbranching papillary formation. The cells are uniform with scant basophilic cytoplasm. The nuclei have smooth nuclear membranes, a fine chromatin pattern, and small nucleoli. It is important to remember that psammoma bodies might be present in cases of endosalpingiosis. The distinction of endosalpingiosis from serous borderline tumor is based on the presence of large papillary clusters with architectural disorganization in the latter. These findings are better appreciated in cell blocks. The presence of nuclear molding and nucleoli in papillary clusters also suggest a neoplastic process. Endometriosis is another potential pitfall. It is characterized by the presence of round to oval cells arranged in 3-dimensional clusters, tubular structures, and sheets. The nuclei are round or bean-shaped with fine chromatin and rare nucleoli. The cytoplasm is scant and vacuolated. The most sensitive finding in endometriosis is the presence of hemosiderin-laden macrophages.

The report format used in peritoneal washings from patients with serous borderline tumors can be problematic. If the patient has a frozen section diagnosis of a serous borderline tumor and the peritoneal washings show the presence of atypical cells, the pathologist might elect to release the report describing the presence of neoplastic cells along with the differential diagnosis, which includes serous borderline tumor and carcinoma. Alternatively, the pathologist could wait for evaluation of the surgical pathology specimen before releasing the final diagnosis. In the setting of a prophylactic salpingo-oophorectomy to reduce the risk of ovarian, tubal, and peritoneal serous carcinoma, it is probably best to finalize the cytology report after reviewing the surgical pathology slides. This reduces the chance of making a false-positive diagnosis. Endosalpingiosis and endometriosis can be reported as benign glandular cells.


To improve the accuracy of cytology in peritoneal washings and serous effusions a series of ancillary studies have been reviewed. Most studies are based on immunocytochemical studies, although there is a limited number of studies using flow cytometry and molecular studies. Immunocytochemical studies can be performed in cytospins, ThinPrep preparations, and cell blocks. (16) There is some controversy on what kind of preparation works the best. Fetsch and colleagues (17, 18) suggested that cell blocks provided the best morphologic interpretation and immunocytochemical study. However, Mulvany4 reportedly obtained superior results with smear preparations. At Memorial Sloan-Kettering Cancer Center (New York, New York), ThinPrep slides are used for immunocytochemical studies in most fluid specimens requiring it. Several panels of antibodies have been proposed in the literature to distinguish cells of mesothelial origin from adenocarcinoma. The antibodies include markers of mesothelial and epithelial origin.

Mesothelial Markers

Mesothelial markers previously evaluated include D240, calretinin, mesothelin, cytokeratin 5/6, WT-1, and HBME-1. D2-40, a monoclonal antibody directed against oncofetal antigen M2A present on cell membranes, has been described as a useful marker of mesothelial cells. It has been shown to have a good sensitivity and specificity for distinguishing epithelioid malignant mesothelioma and reactive mesothelial cells from adenocarcinoma. (19-24) Saad et al (25) found that D2-40 has high specificity and good sensitivity for distinguishing epithelioid mesotheliomas from other primary non-small cell lung carcinomas in pleural fluid cytology. Calretinin, a calcium-binding protein widely expressed throughout the central and peripheral nervous systems, is also expressed by mesothelial cells in the cytoplasm and frequently in the nucleus. Calretinin expression has also been demonstrated in a small fraction of adenocarcinomas. (18, 20-22, 24-40) WT-1 is a DNA-binding protein predominantly located in the nucleus that plays a critical role in the development of the genitourinary tract. In adult tissues, it is expressed by mesangial cells of the kidney, Sertoli cells of the testis, ovarian stromal cells and surface epithelium, mesothelial cells, and some other stromal cells in the female genital tract. WT-1 is also expressed by malignant mesotheliomas and by tumors derived from the ovarian surface epithelium. Although some studies have confirmed the specificity of WT-1 for mesothelioma, several others have demonstrated a low sensitivity. One of the problems concerning WT-1 in the distinction of mesothelial cells from adenocarcinomas is the presence of expression in ovarian serous carcinomas. (25, 40-42) Cytokeratin 5 is expressed by normal mesothelium, squamous and transitional epithelia, and myoepithelial cells in the cytoplasm. Unfortunately, a significant proportion of breast carcinomas also express cytokeratin 5, precluding its use if breast adenocarcinoma involving effusion fluid is in the differential diagnosis. (21, 40, 43) Mesothelin is a surface protein that may be involved in cell-cell adhesion. Its expression is seen in mesothelial cells and surface ovarian epithelial cells and pancreatic ductal carcinomas. (40, 44) HBME-1 is a mouse monoclonal antibody prepared from a human malignant epithelial mesothelioma; however, its specificity is not very high for mesothelial cells. * The markers discussed previously are useful to characterize mesothelial cells and are particularly useful when the cells in question are abundant in the specimen. However, they are not particularly useful in cases in which it is necessary to characterize a small population in an effusion specimen containing abundant mesothelial cells. Negative staining can be due to lack of sensitivity or technical reasons. For these reasons we prefer to use epithelial markers, which can positively identify epithelial cells.

Epithelial-Associated Markers

Antibodies for the detection of epithelial cells include carcinoembryonic antigen (CA) 125, MOC-31, Ber-EP4, CA 19-9, and B72.3. Carcinoembryonic antigen was one of the first antibodies used to distinguish epithelial cells from mesothelial cells. Immunoreactivity varies considerably, depending on the antibody clone and on the range of tumor types used. Mesothelial cells are generally negative for carcinoembryonic antigen staining, as are most carcinomas derived from gynecologic sites, which limits its utility in the evaluation of peritoneal washings from patients thought to have ovarian or endometrial carcinoma. (50-54) Several investigators have also reported that carcinoembryonic antigen stains macrophages and other inflammatory cells owing to nonspecific cross-reactivity and that it has been associated with a 5% to 15% false-positive rate. (10, 31, 32, 47, 49, 55, 56) CA 125 is well established as a tumor marker for ovarian carcinoma, but it can also be expressed in pancreatic and lung carcinomas. (57) CA 125 expression has been shown to have low specificity and low sensitivity in effusion samples. (46, 49) The MOC-31 antibody recognizes an epithelial-associated transmembrane glycoprotein of unknown function in the GLS-1 small cell lung carcinoma cell line and in epithelial tumors. The Ber-EP4 antibody is generated from mice immunized with cells from the MCF-7 breast carcinoma cell line and 2 noncovalently bound glycopeptides. Most studies have documented that MOC-31 and Ber-EP4 are highly effective in distinguishing adenocarcinoma from reactive mesothelial cells, although a few authors have reported possible expression of these markers in mesothelial cells. ([dagger]) CA 19-9 is a sialylated lacto-N-fucopentose II molecule that is related to the Lewis a (Lea) blood group substance. Its expression is usually seen in ovarian and gastrointestinal adenocarcinomas. Ueda et al described that 89% of serous adenocarcinoma samples and none of the reactive mesothelial cells showed immunoreactivity for the CA 19-9 antibody. (49) The monoclonal antibody B72.3 is generated with a membrane-enriched fraction of human mammary carcinoma and recognizes the glycoprotein TAG-72 that is expressed in a wide variety of adenocarcinomas. In a study by Ko et al, B72.3 was expressed in 69% of adenocarcinomas, and it lacked affinity for reactive mesothelial cells. (31)

Immunocytochemistry: Conclusions

There is no single marker that appears sensitive and specific enough to correctly diagnose peritoneal washings. Therefore, a panel of antibodies appears to be the best approach in the discrimination between gynecologic adenocarcinoma and reactive mesothelial cells. Ueda et al (49) recently proposed a combination of MOC-31, Ber-EP4, CA 19-9, and carcinoembryonic antigen antibodies as a suitable panel. MOC-31 and Ber-EP4 appear to be the most effective markers to distinguish adenocarcinoma from mesothelial cells. Mesothelial markers are indicated to distinguish peritoneal involvement by adenocarcinoma from mesotheliomas.

Flow Cytometry and Molecular Studies

The evaluation of flow cytometry and molecular studies in effusion specimens has been limited. (61) Dong et al (62) have shown that it is possible to analyze epithelial and mesothelial markers (Ber-EP4 and epithelial membrane antigen), CD138, and integrin subunits with a 4-color flow cytometer. Holloway et al (63) applied a real-time polymerase chain reaction-based assay involving 17 genes to 13 independent cytologic samples from biopsy-proven malignant mesothelioma and lung adenocarcinomas. They used microarray data for 190 lung adenocarcinomas and 33 malignant mesotheliomas to identify genes differentially expressed between the 2 diseases. Their test was able to distinguish between lung adenocarcinoma and mesothelioma in cells collected from pleural effusions.


In summary, peritoneal effusions may represent major interpretive challenges to the pathologist and their status has important clinical implications. B72.3, MOC-31, and Ber-Ep4 represent the best available markers to identify epithelial cells. Caution is advised to not overdiagnose endometriosis or endosalpingiosis as adenocarcinoma.

Accepted for publication December 11, 2008.


(1.) Tauchi PS, Caraway N, Truong LD, Kaplan AL, Ramzy I. Serous surface carcinoma of the peritoneum: useful role of cytology in differential diagnosis and follow-up. Acta Cytol. 1996;40:429-436.

(2.) Ducatman BBS, Soisson AAP. Peritoneal washing cytology: how significant? Arch Pathol Lab Med. 1997;121:923-924.

(3.) Zuna RE, Behrens A. Peritoneal washing cytology in gynecologic cancers: long-term follow-up of 355 patients. J Natl Cancer Inst. 1 996;88:980-987.

(4.) Mulvany N. Cytohistologic correlation in malignant peritoneal washings: analysis of 75 malignant fluids. Acta Cytol. 1 996;40:1231-1239.

(5.) Willett GD. Prognostic value of cytologic peritoneal washings. Clin Lab Med. 1985;5:265-274.

(6.) Mathew S, Erozan YS. Significance of peritoneal washings in gynecologic oncology: the experience with 901 intraoperative washings at an academic medical center. Arch Pathol Lab Med. 1997;121:604-606.

(7.) Benevolo MM, Mariani LL, Vocaturo GG, Vasselli SS, Natali PPG, Mottolese MM. Independent prognostic value of peritoneal immunocytodiagnosis in endometrial carcinoma. Am J Surg Pathol. 2000;24:241-247.

(8.) Ebina Y, Hareyama H, Sakuragh N, et al. Peritoneal cytology and its prognostic value in endometrial carcinoma. Int Surg. 1997;82:244-248.

(9.) Ayhan A, Taskiran C, Celik C, Aksu T, Yuce K. Surgical stage III endometrial cancer: analysis of treatment outcomes, prognostic factors and failure patterns. Eur J Gynaecol Oncol. 2002;23:553-556.

(10.) Lee A, Baloch ZW, Yu G, Gupta PK. Mesothelial hyperplasia with reactive atypia: diagnostic pitfalls and role of immunohistochemical studies--a case report. Diagn Cytopathol. 2000;22:113-116.

(11.) Zuna RE, Mitchell ML, Mulick KA, Weijchert WM. Cytohistologic correlation of peritoneal washing cytology in gynecologic disease. Acta Cytol. 1989; 33:327-336.

(12.) Ziselman EM, Harkavy SE, Hogan M, WestW, Atkinson B. Peritoneal washing cytology: uses and diagnostic criteria in gynecologic neoplasms. Acta Cytol. 1984;28:105-110.

(13.) Fanning J, Markuly SN, Hindman TL, et al. False positive malignant peritoneal cytology and psammoma bodies in benign gynecologic disease. JReprod Med. 1996;41:504-508.

(14.) Sneige N, Fanning CV. Peritoneal washing cytology in women: diagnostic pitfalls and clues for correct diagnosis. Diagn Cytopathol. 1992;8:632-640, discussion 640-632.

(15.) Ravinsky E. Cytology of peritoneal washings in gynecologic patients: diagnostic criteria and pitfalls. Acta Cytol. 1986;30:8-16.

(16.) Gammon R, Hameed A, Keyhani-Rofagha S. Peritoneal washing in borderline epithelial ovarian tumors in women under 25: the use of cell block preparations. Diagn Cytopathol. 1998;18:212-214.

(17.) Fetsch PA, Abati A, Hijazi YM. Utility of the antibodies CA 19-9, HBME-1, and thrombomodulin in the diagnosis of malignant mesothelioma and adenocarcinoma in cytology. Cancer. 1998;84:101-108.

(18.) Fetsch PA, Simsir A, Abati A. Comparison of antibodies to HBME-1 and calretinin for the detection of mesothelial cells in effusion cytology. Diagn Cy topathol. 2001;25:158-161.

(19.) Bassarova AV, Nesland JM, Davidson B. D2-40 is not a specific marker for cells of mesothelial origin in serous effusions. Am J Surg Pathol. 2006;30:878 882.

(20.) Bhalla R, Siddiqui MT, Mandich D, et al. Diagnostic utility of D2-40 and podoplanin in effusion cell blocks. Diagn Cytopathol. 2007;35:342-347.

(21.) Chu AY, Litzky LA, Pasha TL, Acs G, Zhang PJ. Utility of D2-40, a novel mesothelial marker, in the diagnosis of malignant mesothelioma. Mod Pathol. 2005;18:105-110.

(22.) Lyons-Boudreaux V, Mody DR, Zhai J, Coffey D. Cytologic malignancy versus benignancy: how useful are the "newer" markers in body fluid cytology? Arch Pathol Lab Med. 2008;132:23-28.

(23.) Muller AM, Franke FE, Muller KM. D2-40: a reliable marker in the diagnosis of pleural mesothelioma. Pathobiology. 2006;73:50-54.

(24.) Ordonez NG. The diagnostic utility ofimmunohistochemistryand electron microscopy in distinguishing between peritoneal mesotheliomas and serous carcinomas: a comparative study. Mod Pathol. 2006;19:34-48.

(25.) Saad RS, Lindner JL, Lin X, Liu YL, Silverman JF. The diagnostic utility of D2-40 for malignant mesothelioma versus pulmonary carcinoma with pleural involvement. Diagn Cytopathol. 2006;34:801-806.

(26.) Chhieng DC, Yee H, Schaefer D, et al. Calretinin staining pattern aids in the differentiation of mesothelioma from adenocarcinoma in serous effusions. Cancer. 2000;90:194-200.

(27.) Comin CE, Novelli L, Boddi V, Paglierani M, Dini S. Calretinin, thrombomodulin, CEA, and CD15: a useful combination of immunohistochemical markers for differentiating pleural epithelial mesothelioma from peripheral pulmonary adenocarcinoma. Hum Pathol. 2001;32:529-536.

(28.) Comin CECE, Saieva CC, Messerini LL. h-caldesmon, calretinin, estrogen receptor, and Ber-EP4: a useful combination of immunohistochemical markersfor differentiating epithelioid peritoneal mesothelioma from serous papillary carcinoma of the ovary. Am J Surg Pathol. 2007;31:1139-1148.

(29.) Cook DS, Attanoos RL, Jalloh SS, Gibbs AR. 'Mucin-positive' epithelial mesothelioma of the peritoneum: an unusual diagnostic pitfall. Histopathology. 2000;37:33-36.

(30.) Kitazume H, Kitamura K, Mukai K, et al. Cytologic differential diagnosis among reactive mesothelial cells, malignantmesothelioma, and adenocarcinoma: utility of combined E-cadherin and calretinin immunostaining. Cancer. 2000;90: 55-60.

(31.) Ko EC, Jhala NC, Shultz JJ, Chhieng DC. Use of a panel of markers in the differential diagnosis of adenocarcinoma and reactive mesothelial cells in fluid cytology. Am J Clin Pathol. 2001;116:709-715.

(32.) Lozano MD, Panizo A, Toledo GR, Sola JJ, Pardo-Mindan J. Immunocytochemistry in the differential diagnosis of serous effusions: a comparative evaluation of eight monoclonal antibodies in Papanicolaou stained smears. Cancer. 2001;93:68-72.

(33.) Nagel H, Hemmerlein B, Ruschenburg I, Huppe K, Droese M. The value of anti-calretinin antibody in the differential diagnosis of normal and reactive mesothelia versus metastatic tumors in effusion cytology. Pathol Res Pract. 1998; 194:759-764.

(34.) Okamoto SS, Ito KK, Sasano HH, et al. Ber-EP4 and anti-calretinin antibodies: a useful combination for differential diagnosis ofvarious histological types of ovarian cancer cells and mesothelial cells. Tohoku JExp Med. 2005;206:31 40.

(35.) Politi E, Kandaraki C, Apostolopoulou C, Kyritsi T, Koutselini H. Immunocytochemical panel for distinguishing between carcinoma and reactive mesothelial cells in body cavity fluids. Diagn Cytopathol. 2005;32:1 51-1 55.

(36.) Roberts F, Harper CM, Downie I, Burnett RA. Immunohistochemical analysis still has a limited role in the diagnosis of malignant mesothelioma: a study of thirteen antibodies. Am J Clin Pathol. 2001;116:253-262.

(37.) Sato S, Okamoto S, Ito K, Konno R, Yajima A. Differential diagnosis of mesothelial and ovarian cancer cells in ascites by immunocytochemistry using Ber-EP4 and calretinin. Acta Cytol. 2000;44:485-488.

(38.) Simsir A, Fetsch P, Mehta D, Zakowski M, Abati A. E-cadherin, N-cadherin, and calretinin in pleural effusions: the good, the bad, the worthless. Diagn Cy topathol. 1999;20:125-130.

(39.) Wieczorek TJ, Krane JF. Diagnostic utility of calretinin immunohistochemistry in cytologic cell block preparations. Cancer. 2000;90:312-319.

(40.) Yaziji H, Battifora H, Barry TS, et al. Evaluation of 12 antibodies for distinguishing epithelioid mesothelioma from adenocarcinoma: identification of a three-antibody immunohistochemical panel with maximal sensitivity and specificity. Mod Pathol. 2006;1 9:514-523.

(41.) Hwang H, Quenneville L, Yaziji H, Gown AM. Wilms tumor gene product: sensitive and contextually specific marker of serous carcinomas of ovarian surface epithelial origin. Appl Immunohistochem Mol Morphol. 2004;12:122-126.

(42.) Marchevsky AM, Wick MR. Evidence-based guidelines for the utilization ofimmunostains in diagnostic pathology: pulmonary adenocarcinoma versus mesothelioma. Appl Immunohistochem Mol Morphol. 2007;15:140-144.

(43.) Attanoos RL, Dojcinov SD, Webb R, Gibbs AR. Anti-mesothelial markers in sarcomatoid mesothelioma and other spindle cell neoplasms. Histopathology. 2000;37:224-231.

(44.) Ordonez NG. Value of mesothelin immunostaining in the diagnosis of me sothelioma. Mod Pathol. 2003;16:192-197.

(45.) Ascoli V, Carnovale-Scalzo C, Taccogna S, Nardi F. Utility of HBME-1 immunostaining in serous effusions. Cytopathology. 1997;8:328-335.

(46.) Bateman AC, al-Talib RK, Newman T, Williams JH, Herbert A. Immunohistochemical phenotype of malignant mesothelioma: predictive value of CA125 and HBME-1 expression. Histopathology1997;30:49-56.

(47.) Gonzalez-Lois C, Ballestin C, Sotelo MT, Lopez-Rios F, Garcia-Prats MD, Villena V. Combined use of novel epithelial (MOC-31) and mesothelial (HBME-1) immunohistochemical markers for optimal first line diagnostic distinction between mesothelioma and metastatic carcinoma in pleura. Histopathology. 2001;38:528-534.

(48.) Gumurdulu D, Zeren EH, Cagle PT, et al. Specificity of MOC-31 and HBME-1 immunohistochemistry in the differential diagnosis of adenocarcinoma and malignantmesothelioma: a study on environmental malignantmesothelioma cases from Turkish villages. Pathol Oncol Res. 2002;8:188-193.

(49.) Ueda J, Iwata T, Ono M, Takahashi M. Comparison of three cytologic-preparation methods and immunocytochemistries to distinguish adenocarcinomacells from reactive mesothelial cells in serous effusion. Diagn Cytopathol. 2006;34:6 10.

(50.) Reid-Nicholson M, Iyengar P, Hummer AJ, Linkov I, Asher M, Soslow RA. Immunophenotypic diversity of endometrial adenocarcinomas: implications for differential diagnosis. Mod Pathol. 2006;19:1091-1100.

(51.) McCluggage WG, Sumathi VP, McBride HA, Patterson A. A panel of immunohistochemical stains, including carcinoembryonic antigen, vimentin, and estrogen receptor, aids the distinction between primary endometrial and endocervical adenocarcinomas. Int J Gynecol Pathol. 2002;21:11-15.

(52.) Castrillon DH, Lee KR, Nucci MR. Distinction between endometrial and endocervical adenocarcinoma: an immunohistochemical study. Int J Gynecol Pathol. 2002;21:4-10.

(53.) Torenbeek R, Lagendijk JH, Van Diest PJ, Bril H, van de Molengraft FJ, Meijer CJ. Value of a panel of antibodies to identify the primary origin of adenocarcinomas presenting as bladder carcinoma. Histopathology. 1998;32:20-27.

(54.) Lagendijk JH, Mullink H, Van Diest PJ, Meijer GA, Meijer CJ. Tracing the origin of adenocarcinomas with unknown primary using immunohistochemistry: differential diagnosis between colonic and ovarian carcinomas as primary sites. Hum Pathol. 1998;29:491-497.

(55.) Dejmek A, Hjerpe A. Reactivity of six antibodies in effusions of mesothelioma, adenocarcinoma and mesotheliosis: stepwise logistic regression analysis. Cytopathology. 2000;11:8-17.

(56.) Queiroz C, Barral-Netto M, Bacchi CE. Characterizing subpopulations of neoplastic cells in serous effusions: the role of immunocytochemistry. Acta Cytol. 2001;45:18-22.

(57.) Nap M. Immunohistochemistry of CA 125. Unusual expression in normal tissues, distribution in the human fetus and questions around its application in diagnostic pathology. Int JBiol Markers. 1998;13:210-215.

(58.) Hecht JL, Pinkus JL, Pinkus GS. Monoclonal antibody MOC-31 reactivity as a marker for adenocarcinoma in cytologic preparations. Cancer. 2006;108:56 59.

(59.) Morgan RL, De Young BR, McGaughy VR, Niemann TH. MOC-31 aids in the differentiation between adenocarcinoma and reactive mesothelial cells. Cancer. 1999;87:390-394.

(60.) Selvaggi SM. Diagnostic pitfalls of peritoneal washing cytology and the role of cell blocks in their diagnosis. Diagn Cytopathol. 2003;28:335-341.

(61.) Finn CB, Ward K, Luesley DM, Dunn JA, Redman CW. Qualitative and quantitative analysis of peritoneal fluids from women with gynecologic diseases: comparison of cytology and flow cytometry for the detection of malignancy in lavage and ascitic fluids. Anal Quant Cytol Histol. 1991;13:182-186.

(62.) Dong HP, Holth A, Berner A, Davidson B, Risberg B. Flow cytometric immunphenotyping of epithelial cancer cells in effusions -- technical considerations and pitfalls. CytometryB Clin Cytom. 2007;72:332-343.

(63.) Holloway AJ, Diyagama DS, Opeskin K, et al. A molecular diagnostic test for distinguishing lung adenocarcinoma from malignant mesothelioma using cells collected from pleural effusions. Clin Cancer Res. 2006;12:5129-5135.

* References 10, 17, 18, 27, 29, 32, 35, 36, 40, 42, 45-49.

([dagger]) References 22, 24, 32, 40, 46-48, 55, 58, 59.

Oscar Lin, MD, PhD

From the Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, New York.

The author has no relevant financial interest in the products or companies described in this article.

Presented in part at the Surgical Pathology of Neoplastic Diseases course, Memorial Sloan-Kettering Cancer Center, New York, New York, May 12-16, 2008.

Reprints: Oscar Lin, MD, PhD, Department of Pathology, Memorial Sloan-Kettering Cancer Center, 1275 York Ave, New York, NY 10065 (e-mail:
Gale Copyright: Copyright 2009 Gale, Cengage Learning. All rights reserved.