{"paper_id":"ca5d6c64-a272-44e0-bf4a-2a39a75f1314","body_text":"This may be the author’s version of a work that was submitted/accepted\nfor publication in the following source:\nShield, Paul W.\n(2004)\nPeritoneal washing cytology.\nCytopathology, 15(3), pp. 131-141.\nThis file was downloaded from: https://eprints.qut.edu.au/92528/\n© Copyright 2004 Blackwell Publishing Ltd\nThis work is covered by copyright. Unless the document is being made available under a\nCreative Commons Licence, you must assume that re-use is limited to personal use and\nthat permission from the copyright owner must be obtained for all other uses. If the docu-\nment is available under a Creative Commons License (or other specified license) then refer\nto the Licence for details of permitted re-use. It is a condition of access that users recog-\nnise and abide by the legal requirements associated with these rights. If you believe that\nthis work infringes copyright please provide details by email to qut.copyright@qut.edu.au\nNotice: Please note that this document may not be the Version of Record\n(i.e. published version) of the work. Author manuscript versions (as Sub-\nmitted for peer review or as Accepted for publication after peer review) can\nbe identified by an absence of publisher branding and/or typeset appear-\nance. If there is any doubt, please refer to the published source.\nhttps://doi.org/10.1111/j.1365-2303.2004.00140.x\n\n1 \nReview Article: Peritoneal Washing Cytology \nPaul Shield \nChief Scientist \nCytology Department \nSullivan Nicolaides Pathology \n134 Whitmore St \nTaringa, Brisbane, Queensland Australia 4068 \npaul_shield@snp.com.au \nRunning Title: Peritoneal Washing Cytology \n\n2 \nAbstract \nPeritoneal washing cytology (PWC) is a useful indicator of ovarian surface \ninvolvement and peritoneal dissemination by ovarian tumours. It may identify \nsubclinical peritoneal spread and thus provide valuable staging and prognostic \ninformation, particularly for non-serous ovarian tumours. The role of PWC as \na prognostic indicator for endometrial carcinoma is less clear, due in part to \nthe questionable significance of identifying endometrial tumour cells in the \nperitoneum. \nDetection of metastatic carcinoma in PWC is based on recognition of non-\nmesothelial cell characteristics, however a number of conditions such as \nreactive mesothelial cells, endometriosis and endosalpingiosis may mimic this \nappearance. Cells from these conditions may have a similar presentation in \nPWC to that of serous borderline tumours and low grade serous carcinoma. \nThe presence of cilia, lack of single atypical cells, prominent cytoplasmic \nvacuolation, marked nuclear atypia or two distinct cell populations are features \nfavouring a benign process. Attention to these features along with close \ncorrelation with clinical history and the results of surgical pathology should \nhelp avoid errors. Additional assistance may be provided by the use of cell \nblocks and special stains. \n \nKeywords: Peritoneal Washing, Peritoneum, Cytology, Gynaecological \nMalignancy, Immunocytochemistry\n\n3 \n \nIntroduction \nPeritoneal dissemination by gynaecological malignancies, particularly ovarian \ntumours, often manifests in malignant ascites. Microscopic peritoneal seeding \nwith tumour cells predates the formation of ascites and its detection by \nperitoneal washing cytology (PWC) may provide valuable staging and \nprognostic information. Identification of patients with occult (microscopic) \nperitoneal dissemination may be useful in defining a group of patients that \nwould benefit from different treatment. The technique of intraoperative \nperitoneal washing cytology was introduced in 1956 by Keetle and Elkin 1. In \n1975 the International Federation of Gynecologists & Obstetricians (FIGO) \nincorporated results of PWC into the staging classification for ovarian \ncarcinoma and in 1989 for endometrial carcinoma. The technique may also be \nuseful in identifying recurrent or persistent cancer and has been applied to a \nvariety of non-gynaecological cancers.  \n \nThis review discusses the role of PWC and its morphological interpretation for \nthe most common malignancies encountered. Pitfalls in diagnosis and \nadjunctive techniques are also reviewed. \n\n4 \nPreparation and Specimen Adequacy  \nSpecimen adequacy in PWC is poorly defined. DeMay2 points out that the \nmajority of published series contain no cases reported as unsatisfactory while a \nfew have   surprisingly high rates. Low cellularity may be a cause of false \nnegative results 3. \n \nPeritoneal washing specimens are frequently heavily contaminated with blood \nand methods to concentrate diagnostic cells are essential.  Several methods, \nincluding Carnoy’s fixation and gradient density centrifugation have been \nreported. Mulvaney\n4 used Ficoll gradient density centrifugation to achieve this \nand reported only 1.5% (9/613) of specimens inadequate for interpretation.  \n \nIn our laboratory we find blood removal is almost always required for PW \nspecimens. Specimens are centrifuged, the supernatant discarded and two \ndirect smears are prepared. One is fixed in 95% alcohol for Pap staining and \nthe other air-dried for rapid Giemsa staining.  If the specimen is bloody, the \nremaining pellet is then resuspended in a Hanks/methanol solution (HMS: 1 \npart methanol; 2 parts Hank’s balanced salt solution; 3 parts distilled water) \nand agitated for 10 minutes. This step is highly effective at lysing the red \nblood cells without significantly altering cellular arrangements or morphology. \nThe solution is then centrifuged again and if a pellet is visible then a direct \nsmear is prepared and alcohol fixed. If only a scanty pellet remains, the \nmaterial is processed as a cytospin for Pap staining. This processing allows \n\n5 \nevaluation of the specimen in its ‘native’ state as well as concentrating \ndiagnostic cells from a large proportion of the submitted sample. In our \nexperience it results in a very low proportion of specimens reported as ‘blood \nonly’. \n \nApplications \nAlthough positive PWC is useful for documenting the presence of malignant \ncells in the peritoneum, this is not always of prognostic significance. Positive \nPWC is generally seen in patients with a poor prognosis, however for some \nprimary sites this is not an independent factor, but rather is associated with \nother prognostic indicators such as lymph node involvement and deep stromal \ninvasion. Additionally, not all free cancer cells in the peritoneum survive and \nestablish intraperitoneal metastases.  \n \nBenign Findings \nPeritoneal washing specimens are generally highly cellular with mesothelial \ncells arranged in monolayered sheets. The cells are regularly spaced with a \nmoderate amount of cytoplasm, usually forming pavement-like sheets (Figure \n1). Nuclei may vary considerably in size from sheet to sheet but are usually \nlocally uniform with fine, even chromatin and small nucleoli (Figure 2). \nNuclear longitudinal grooves and sometimes-folded nuclear membranes may \nbe seen (Figure 3). The latter are said to be more common in mid-cycle\n2. The \nmost common pattern is numerous, sometimes quite large, sheets of \n\n6 \nmesothelial cells with minimal leucocytes and single cells. Variations on this \npattern include increased numbers of single cells, including macrophages, \nleucocytes and mesothelial cells, and, in reactive conditions, the presence of \nsmaller, rounded groups with greater depth of focus.  \n \nOther benign findings include skeletal muscle fragments and collagen balls. \nSo-called collagen balls (Figure 4) are spheroids of collagen surrounded by a \nsingle layer of mesothelial cells\n5. In Papanicolaou stained preparations they \nappear as distinctive aqua coloured balls of homogenous material. By focusing \nthrough the ball it is possible to identify its rounded nature and the single layer \nof mesothelial cells with bland nuclei. Examination of surgical specimens \nsuggests that collagen balls originate from minute papillary stromal projections \non the surface of the ovary that are covered with mesothelium5. Wojcik and \nNaylor5 reported finding collagen balls in 4.5% of 418 peritoneal washing \nspecimens. In our experience they are seen much more frequently. Review of \n80 consecutive specimens identified collagen in balls in 48%, occurring in \nalmost half of both benign and malignant specimens. This higher frequency \nmay be the result of the thorough sampling of the specimen provided by our \npreparation method. Although they are listed as a possible cause for false \npositive diagnoses by some authors\n5,6, collagen balls are usually an easily \nrecognised incidental benign finding. \n \n\n7 \nBenign Gynaecological Disease \nAlthough PWC may identify occult carcinoma during surgery for benign \ndisease the incidence of this is very low. Several large series have failed to \nfind any cases with positive PWC amongst patients with benign \ngynaecological disease \n7,8,9.   \n \nOvarian Tumours \nFor ovarian tumours positive PWC is a sensitive indicator of ovarian surface \ninvolvement and peritoneal dissemination and will detect a high proportion of \npatients with subclinical intraperitoneal extension10. The technique provides \nwider sampling of the peritoneum than random staging biopsies. Several \nauthors have reported positive PWC in cases of ovarian borderline tumours of \nlow malignant potential (LMP) without other evidence of peritoneal implants \nor ovarian surface involvement\n4,10.  \n \nPeritoneal washing cytology plays a valuable role in the staging of ovarian \ntumours. Four year survival of patients with ovarian carcinoma has been \nshown to be significantly different depending on PWC regardless of other \nparameters11. Mulvaney4  reported 63% (5/8) of borderline ovarian tumours \nand 50% (3/6) of non-serous ovarian malignancies were upstaged as a result of \nPWC results. However for serous carcinomas, only 7% (1/14) were upstaged \non PWC, probably due to the clinically obvious dissemination of tumours on \npresentation. \n\n8 \n \nMorphologically, ovarian epithelial tumours show a spectrum from benign \ncystadenomas through low malignant potential (borderline) tumours to \nmalignant adenocarcinomas. Borderline tumours constitute about 10-15% of \nserous tumours and histologically show epithelial proliferation with \nstratification and tufting but lack destructive stromal invasion. About a third \nare associated with peritoneal implants, both invasive and non-invasive\n12. \nBorderline tumours have a better prognosis and generally are managed more \nconservatively and their distinction from low grade adenocarcinomas in PW \nspecimens may therefore be important.  \n \nBorderline tumours tend to present in PW specimens as large, smooth \nbordered, papillary fragments composed of small uniform cells with high N/C \nratio and inconspicuous nucleoli (Figure 5). Mitotic figures and cytoplasmic \nvacuoles are infrequent. Psammoma bodies may be seen in the PWC of half to \ntwo thirds of cases\n4,13,14,15.   \n \nBy contrast, the PWC of invasive ovarian carcinoma is characterised by \nsmaller, less cohesive papillary fragments of cells with irregular borders. \nIndividual cells are relatively larger and more pleomorphic with a low N/C \nratio and abundant cytoplasmic vacuoles (Figure 6). In general PWC \npreparations are more cellular than seen in borderline tumours with frequent \n\n9 \nsingle cells and mitoses. Adenocarcinomas are also more likely to be \nanueploid14. \n \nAlthough these general morphological differences exist and some studies have \nsuggested that a distinction between borderline serous tumours and frank \nadenocarcinomas is possible\n15, most studies of low grade carcinoma have \nconcluded that in practice it is not possible to separate them from ovarian LMP \ntumours in PWC due to the overlap in features\n10,12,14,16. Correlation with \nhistology results from surgical specimens is therefore an essential step. \n \nCytological typing of ovarian tumours is not usually required, as surgical \nspecimens provide more reliable classification. Serous, mucinous and \nendometrioid tumours all generally show typical cytological features of \nadenocarcinoma. Although some features are more commonly expressed in \ncertain tumours, such as psammoma bodies in serous tumours and mucin in \nmucinous tumours, there are no specific features\n17. Clear cell carcinomas are \nsomewhat distinctive cytologically, usually showing single cells and sheets of \ncells with abundant finely vacuolated cytoplasm and round nuclei with \nprominent nucleoli (Figure 7). The cells may form small to medium-sized, \nrounded groups of cells surrounding metachromatic interluminal  material4,16. \nIn mixed Mullerian tumours it is usually the epidermal component that is \npresent in PWC specimens. Germ cell tumours are usually easily recognised as \n\n10 \nmalignant, although some, such as yolk sac tumours, may closely resemble \nadenocarcinoma18. \n \nEndometrial Tumours \nUnlike ovarian carcinoma, the role of PWC for endometrial carcinoma is not \nas clear cut.  There is a significant increase in the incidence of abnormal PW in \nadvanced stage disease (about 30% positive for stage III/IV compared with \naround 10% for stage I). However in advanced disease positive PWC may \nsimply be a manifestation of extrauterine spread rather than an independent \npoor prognostic factor. It is in cases of early stage (I) disease where positive \nPWC could be of most prognostic importance. Unfortunately for Stage I \nendometrial carcinoma there are inconsistent results reported. Some series \nhave shown significantly better survival rates if PWC is negative\n1,19,20,21,22, \nhowever others have found no correlation of other histological parameters with \npositive PWC or with poorer survival23,24. Yet again, some series have \nreported correlation of positive PWC with some histological parameters but \nnot with outcome\n25,26,27. These studies found PWC to be correlated with depth \nmyometrial invasion, histological grade, cervical involvement and vascular \nchannel involvement but not histologic subtypes, grade, adnexal or lymph \nnode involvement.  \n \nIn part this lack of clear-cut significance may be related to the mode of tumour \ncell spread from endometrial tumours to the peritoneum and to the variable \n\n11 \nimplications of tumour cells in the peritoneum. In the case of endometrial \ncancer, malignant cells identified in the peritoneum may not necessarily equal \nestablished metastatic disease.  \n \nThe methods by which malignant cells reach the peritoneum is also of interest. \nIn early stage disease where the tumour is otherwise confined to the uterus, the \nfallopian tube represents the most likely conduit. Menczer et al\n28 reported \npositive tubal cytology in 22% of patients with endometrial carcinoma of all \nstages but positive PWC in only 8.5%. Seventy-five percent of patients with \npositive PWC had negative tubal cytology. In a study of fallopian tube \nwashings, Mulvaney et al\n4 found  positive fallopian tube cytology with \npositive PWC in  72%. Metastasis via the lymphatics and haematogenous \nspread account for some peritoneal seeding as evidenced by cases of \nendometrial carcinoma with a history of BSO that develop positive PWC\n29. \nLymphatic spread, as well as release of tumour cells from areas of serosal \ninvasion has also been proposed as a method of peritoneal spread for gastric\n30 \nand pancreatic cancer31. However, although some studies have found a \ncorrelation between positive PWC and vascular invasion for endometrial \ncancer26,32, others have not27. Transtubal retrograde dissemination, for example \nduring hysteroscopy, may be responsible for the presence of malignant cells in \nsome cases of early stage endometrial carcinoma that are otherwise confined to \nthe uterus. Sagawa et al33 compared peritoneal cytology pre- and \nposthysterosopy and concluded that hysteroscopy resulted in 12.5% of cases \n\n12 \nhaving positive PWC. Sonada et al34 reported on 377 cases of Grade I/II \nendometrial carcinoma with no extrauterine spread. They found significantly \nmore cases (independent of other prognostic factors) had positive PWC \nfollowing laproscopic assisted vaginal hysterectomy (10%) than patients \nundergoing TAH (2.8%).  \n \nSome authors have attempted to correlate the morphology of tumour cells \nidentified in PWC with outcome. Yanoh et al\n35 concluded that cases with no \nevidence seeding and good outcome generally were less cellular; had less \nisolated cells and less groups with scalloped edges (Figure 8). Many of the \ncases that failed to develop macroscopic peritoneal disease showed sparse \nsmall 3-dimensional groups of cells with a morphology similar to that seen in \nendometrial carcinoma exfoliating and collected in Pap smears. A \npredominance of isolated cells in large numbers is also correlated with poor \noutcome in gastric\n36 and pancreatic31 carcinoma. \n \nCervical Tumours \nPWC is of limited value for cervical carcinoma because peritoneal \ninvolvement generally occurs relatively late in the development of these \ntumours, with deep stromal and vascular involvement of more significance\n11. \nMulvaney37 reported several cases of cervical carcinoma that were upstaged as \na result of positive PWC, however these patients had nodal metastases and \ntheir treatment was not altered. Adenocarcinomas of the cervix are more likely \n\n13 \nto yield positive PWC than squamous tumours37,38, as are recurrent cervical \ncarcinoma cases3.  SCC is rarely identified in PW specimens and most \ncommonly presents as poorly differentiated malignant cells38 . \n \nLess Common Tumours \nAs well as carcinomas metastatic to the ovary, such as breast and colonic \nadenocarcinomas, fallopian tube cancer and primary peritoneal carcinoma are \noccasionally encountered in PWC. Serous papillary neoplasms may arise in the \novary, fallopian tube, endometrium and primary to the peritoneum. It is not \neasy to distinguish between the tumours on the basis of immunocytochemical \nprofile\n39 or cytomorphology- all have in common the features of single cells \nand three dimensional groups of cells with round nuclei, single nucleoli, \nabundant, often vacuolated cytoplasm and sometimes psamomma bodies40.  \n \nNon-Gynaecological Malignancies \nFor gastric cancer, PWC provides clinically useful information. Positive PWC \nis associated with poor outcome for gastric cancer patients41,42. Patients with \notherwise resectable gastric cancer and positive PWC have a survival \ncomparable to stage IV tumours, even in the absence of macroscopic \nperitoneal disease and despite resection of all gross disease\n41,42.  \n \nIn pancreatic cancer, positive PWC is associated with advanced disease and \nmay identify patients with occult peritoneal disease but is not an independent \n\n14 \nrisk factor31,43. Cases of long term survival, even with positive PWC have been \nreported and it is therefore not considered an indicator for non-resection31. For \ncolonic cancer44 and cholangiocarcinoma45 positive PWC is not an \nindependent prognostic indicator.  \n \nPitfalls \nInterpretive difficulties arise when a population of cells is present that appears \ndifferent to the usual presentation of flat sheets of mesothelial cells. In addition \nto metastatic tumour, this may result from benign epithelium occurring in the \nperitoneum, such as Mullerian inclusions and fallopian tube epithelium, cells \nbeing spilt from ruptured cysts or due to reactive mesothelial changes. Benign \nreactive changes may be encountered in association with adhesion formation, \npelvic inflammatory disease, endometriosis, ectopic pregnancy, adnexal \ninfarction due to torsion, tubal abcess and hydrosalpinx. \n \nMesothelial Cells \nMesothelial cells, in all their various guises, pose the most common problems \nin PWC. In most cases the regular sheet-like arrangement of mesothelial cells \nthat is characteristic of PWC makes their identification and discrimination \nfrom carcinoma easier than in effusion specimens where mesothelial cells are \ntypically more rounded and the groupings more three dimensional. However \nlarge folded sheets of mesothelial cells in PW can sometimes mimic the \npapillary arrangements of carcinoma. Careful examination usually reveals the \n\n15 \nflat, single-cell layering characteristic of benign mesothelial sheets. The often-\nmarked variation in nuclear size amongst different groups of mesothelial cells \nin the same preparation may also contribute to their misinterpretation. \nHowever the cohesiveness, regular spacing and local uniformity of nuclei are \nuseful in correctly identifying their benign nature. \n \nReactive mesothelial cells may be encountered in PW specimens, but more \ncommonly in peritoneal effusions. They result of a wide variety of conditions, \nsuch as inflammatory conditions, endometriosis, ectopic pregnancy, tubo-\novarian abcess, pelvic tumour, chemo- and radiotherapy and cirrhosis16,46,47. \nTight clusters of mesothelial cells may mimic low grade and borderline \ntumours with smooth edged groups of cells with tightly packed nuclei and high \nN/C ratios (Figure 9). Identification of a predominantly monolayered \narrangement (Figure 10), fine, even chromatin and a gradation of cellular \nchange from cells with typical mesothelial characteristics to those with \nreactive features\n46 are helpful in recognising reactive change. Nevertheless, \nsome cases demonstrate marked changes including prominent nucleoli and \ncells groups with considerable depth of focus and sometimes psammoma \nbodies. This can make discrimination from borderline and low grade tumours \ndifficult (Figure 11). In some of these cases cell block preparations, \nimmunocytochemistry or awaiting the results of surgical specimens are \nnecessary to reliably identify the cell type. It should be emphasised that \n\n16 \npsammoma bodies may be seen in a variety of benign conditions as well as \nborderline, invasive, and non-gynaecological tumours. \n \nEndometriosis \nThe presence of endometrial glandular and stromal cells together with \nhaemosiderophages is said to be diagnostic of endometriosis2. However \nendometrial cells and haemosiderophages are seen together in only about 30% \nof patients with laporoscopically confirmed endometriosis\n48. Haemosiderin-\nladen macrophages alone are seen in about another third of patients with \nconfirmed pelvic endometriosis. Although they are a non-specific finding that \nmay be seen in any condition associated with leakage of blood into the \nperitoneum, in young patients lacking other causes for haemorrhage, \nhaemosiderophages are highly suggestive of endometriosis\n48.  \n \nEndometrial cells are difficult to reliably identify, as they may be similar in \npresentation to mesothelial cells or lymphoid cells48. Perhaps the most reliable \nmethod of identifying them is in cell block preparations where the epithelial \nand stromal elements may be seen6.  \n \nThe most common difficulty caused by endometriosis is the presence of \nreactive mesothelial cells2,3,16. These may form large aggregates (Figures 12 & \n13), sometimes with calcific concretions, mimicking serous tumours. \nConsideration of clinical history and observation of the mesothelial \n\n17 \ncharacteristics of these groupings, such as limited depth of focus and \nuniformity of nuclear features and spacing, together with haemosiderophages \nare necessary to avoid false positive diagnoses. \n \nEndosalpingiosis \nEndosalpingiosis (Mullerian inclusions) is characterised by ectopic benign \nepithelium identical to fallopian tube epithelium. Endosalpingiosis is \nfrequently multicentric, most commonly occuring in the pelvic peritoneum, \nlymph nodes and omentum and is thought to arise from a metaplastic process \nof the coelomic epithelum.  \n \nIt is a potential cause for false positive diagnoses\n3,49,50 as cytologically the \ncells from endosalpingioisis may present as tightly cohesive papillary \nfragments of cells that contrast with benign mesothelial cells. The cell \naggregates are most commonly tubular or papillary and often surround \npsammoma bodies (Figures 14 & 15). Free psammoma bodies may be seen but \nsingle cells are usually lacking. Like reactive mesothelial cells, although the \ncells may have an increased N/C ratio and more prominent nucleoli, the \nepithelial groupings are usually single-layered with uniform, well spaced \nnuclei. In some cases cilia may be identified (Figure 16). The presence of more \nthan mild to moderate nuclear atypia, complex branching architecture, single \natypical cells or mitotic activity should weigh against a diagnosis of \nendosalpingiosis\n49,50 . \n\n18 \n \nCell Blocks and Special Stains \nCell blocks provide a useful adjunct to cytological preparations of PWC6. \nThey allow additional sampling of the specimen, assessment of \nmicroarchitecture and provide the optimal preparations for the performance of \ncytochemical and immunocytochemical (ICC) stains51. Cell blocks also \nprovide a means for longer term ‘storage’ of material. \n \nSeveral studies have reported improvements in sensitivity for detection \nmalignant cells in PWC in gastric\n52,53 and pancreatic54,55 cancer by using ICC \nto a range of carcinoma markers, including B72.3, CEA and CA 19-9. The \nsame markers for metastatic carcinoma that are of value in effusion cytology \nare useful for PWC. These are best employed in a panel. The most useful of \nthese markers include stains for CEA, B72.3, Ber Ep4, CD 15 and MOC-\n31\n39,56. Identification of neutral mucin with PAS diastase staining is also \nuseful. \n \nCalretinin is a useful marker for mesothelial cells\n57. A small proportion of \ncarcinomas, such a poorly differentiated colonic adenocarcinomas, express \ncalretinin, but most carcinomas are negative\n39,58,59. Even though the ovarian \nsurface epithelium is calretinin positive, less than 10% of serous carcinomas \nare focally positive for calretinin39.  Wieczorek and Krane60 studied the value \nof calretinin in distinguishing serous borderline tumours from reactive \n\n19 \nmesothelial cells and concluded that it was not useful. This was because of the \nfrequent presence of admixed reactive mesothelial cells that will stain positive, \nand due to the variable staining of both borderline tumours and mesothelial \ncells. They reported that strips of benign mesothelial cells in PW specimens \nstain weakly or not at all for calretinin, whereas reactive and malignant \nmesothelial cells stain strongly. Serous tumours were usually negative but may \nshow focal positivity with granular cytoplasmic staining, whereas mesothelial \ncells have nuclear and cytoplasmic staining, often more intense on the \nmembrane, producing the characteristic ‘fried egg’ appearance\n61. Cytokeratin \n5/6 staining is another marker of mesothelial differentiation39 that appears \nmore consistently expressed in normal mesothelial cells and is probably best \nused in a panel with calretinin and epithelial markers. \n \nSummary \nDetection of tumours in PWC relies on the identification of non-mesothelial \narrangements and cells. High grade carcinoma is easily identified. However \ndifficulties arise with groups of cells that are not of typical mesothelial nature, \nparticularly when there is an absence of single cells or marked nuclear atypia \nbut raised N/C ratio and small to prominent nucleoli (with or without \npsammoma bodies).  This raises the differential diagnosis of reactive \nmesothelial cells, endosalpingiosis, borderline serous tumour, low grade serous \ncarcinoma. The morphology of these conditions shows considerable overlap \nand close attention to clinical history is essential. \n\n20 \n \nFeatures favouring benign include: cilia, no single cells, few cells with \ncytoplasmic vacuolation, absence of mitotic activity and two distinct \npopulations not identified. \n \nIn cases with equivocal cytological findings correlation with surgical \nspecimens is an essential step. \n2,16,48,61 \n\n21 \nReferences \n1. Keetle WC and Elkin HB. Experience with radioactive colloidal gold in the \ntreatment of ovarian carcinoma. 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Doglioni C, Chiodera PL, Furlanettto A et al.  Calretinin: a specific marker \nfor evaluation of serous effusions (abstract). Mod Pathol 1997;10:33A. \n\n28 \n59. Gotzos V, Vogt P, Celio MR. The calcium binding protein calretinin is a \nselective marker for malignant pleural mesotheliomas of epithelial type. Pathol \nRes Pract 1996;192:137-147. \n60. Wieczorek TJ, Krane JF. Diagnostic utility of calretinin \nimmunohstochemistry in cytologic cell block preparations. Cancer Cytopathol \n200;90:312-319. \n61. Chhieng DC, Yee H, Schaefer D et al. Calretinin staining pattern aids in \nthe differentiation of mesothelioma from adenocarcinoma in serous effusions. \nCancer 2000;25:194-200. \n62. Covell JL, Carry JB, Feldman PS. Peritoneal washings in ovarian tumours: \nPotential sources of error in cytologic diagnosis. Acta Cytol 1985;29:310-316. \n \n\n29 \n \nFigure 1. A sheet of benign mesothelial cells arranged in a \nmosaic pattern with distinct cytoplasmic borders. (Pap; \nx40 Obj) \n \n \n \n \nFigure 2. Sheet of mesothelial cells. Note that although \nvariation in nuclear size is apparent throughout the sheet, \nnuclei are locally uniform. (Diff Quik; x20 Obj) \n \n \n \n \n \nFigure 3. Benign mesothelial cells with highly irregular \nnuclear membranes and longtitudinal nuclear grooves. \n(Pap; x40 Obj) \n \n \n \n \n\n\n30 \nFigure 4. Collagen ball. Note the bland mesothelial \ncell nuclei arranged around a hyaline globule of \ncollagen. (Pap; x40) \n \n \n \n \n \n \nFigure 5. A grouping of cells from an ovarian \nserous borderline tumour. Note the uniform \nhyperchromatic nuclei and high N/C ratio. (Pap; \nx20) \n \n \n \n \nFigure 6. Cell grouping from serous papillary \ncarcinoma of ovary. Note irregular outline of \ngroup and cytoplasmic vacuolation. (Pap; x20) \n \n\n\n31 \n \nFigure 7. Clear cell carcinoma of ovary. Note \ncells with abundant finely vacuolated cytoplasm \nsurrounding metachromatic material. (Pap; x20 \nObj) \n \n \n \n \nFigure 8. Endometrial adenocarcinoma. \nCohesive 3-dimensional grouping of cells with \nlarge cytoplasmic vacuoles. (Pap; x40 Obj) \n \n \n \n \n \nFigure 9. Reactive mesothelial cells with high \nN/C ratio but forming a monolayered sheet. \n(Pap, x40 Obj) \n \n \n\n\n32 \n \nFigure 10. Sheet of reactive mesothelial cells. \nNote ‘windows’ between cells and monolayered \narrangement. (Pap stain, x40 Obj) \n \n \n \n \n \n \n \n \n \nA       B  \nFigure 11. Morphological similarity between low grade serous papillary \ncarcinoma of ovary (A) and reactive mesothelial cells (B) from a benign \ninflammatory specimen. (both x20 Obj). \n \n \n \nFigure 12. Focus of peritoneal endometriosis with \nendometrial epithelial and stromal tissue and calcific \nconcretions. (H&E, x10 Obj) \n\n\n33 \n \n \nFigure 13. Peritoneal washing from the same \npatient as Fig 11, showing reactive mesothelial \ncells and haemosiderophages. (Pap, x40 Obj) \n \n \n \n \n \nFigure 14. Focus of endosalpingiois in a \nperitoneal biopsy. Note benign columnar \nepithelium and calcific concretions. (H&E, x10 \nObj) \n \n \n \n \nFigure 15. Peritoneal washing from the same case as \nFig 14. Note large sheet of cells and psammoma \nbodies. (Pap stain, x40 Obj) \n \n \n\n\n34 \n \n \nFigure 16. Ciliated epithelial cells in a peritoneal \nwashing from a patient with endosalpingiosis. \n(Pap, x40 Obj).","source_license":"CC0","license_restricted":false}