Cytopathology of serous neoplasia of the ovary and the peritoneum: differential diagnosis from mesothelial proliferations

Role of Ancillary Techniques in Reporting Serous Fluid Cytology - "Redefining Categories, Refining Diagnosis"

Background

The "International System of Reporting Serous Fluid Cytology (TIS)" together with cytomorphology promotes the use of ancillary techniques to resolve difficulties in reporting serous fluid cytology.

Objective

To classify serous effusion fluid samples received at our department in line with "TIS", indicating the risk of malignancy (ROM), and directing appropriate usage of ancillary testing.

Materials and Methods

Prospective study carried out from October 2021 to September 2022. The study included all pleural, ascitic, and pericardial fluid samples, reported according to 'TIS'. Flow cytometry and immunocytochemistry were ancillary methods utilized to assist in reporting. Cases with available history and convincing correlations didn't require further assessment.

Results

A total of 1200 serous effusion samples were evaluated including 604 pleural, 591 ascitic, and 5 pericardial fluid samples. After categorization, there were 23 samples in non-diagnostic (ND, 1.9%), 575 in negative for malignancy (NFM, 47.91%), 44 in atypia of undetermined significance (AUS, 3.66%), 64 in suspicious for malignancy (SFM, 5.33%), and 494 in malignant category (MAL, 41.16%). Ancillary studies were beneficial in the recategorization of 26% (11/44) AUS cases, 29.6% (19/64) SFM cases, and it helped refine tumor characteristics in 35.42% (175/494) cases categorized as malignant. Final ROM calculated for each category: ND 25%, NFM 18.6%, AUS 66.6%, SFM 88%, and MAL 100%.

Conclusion

Serous fluid is an easily obtainable sample that can provide opportunities for ancillary testing with clinical implications. In AUS and suspicious category although, diagnostic yield is increased however, a larger number of cases are required to obtain definite results.

Approach to Diagnostic Cytopathology of Serous Effusions

Collection of most serous fluids from various effusions is a relatively simple procedure. Because of this, serous fluids are commonly submitted for pathologic examination including cytopathologic evaluation by various clinical institutions. As a consequence, even a general pathology laboratory which may not have expertise with highly trained cytopathologist would be confronted with serous fluids for cytologic evaluation.

However, cytopathologic evaluation of serous fluids is complex as compared to evaluation of fine needle aspiration cytology. This signifies the fact that all pathologists, irrespective of subspeciality cytopathology training and level of subspeciality expertise, should be conversant with the diagnostic challenges and pitfalls of effusion fluid cytology.

Although, majority of effusions are due to reactive and non-neoplastic etiologies, cancer is one of the causes of an effusion as a manifestation of advanced cancer. Detecting neoplastic cells in effusion specimens in most of clinical settings is related to the advanced status of the disease, which usually is equivalent to incurable stage. Thus, interpretation of cytopathology as positive for cancer cell is highly critical in planning the trajectory of the clinical management with an obvious negative impact of false positive interpretation.

Apart from cancer, effusions may be secondary to hemodynamic pathologies such as heart failure, hypoalbuminemia, cirrhosis etc. in addition to the different inflammatory conditions including parasitic infestations, bacterial, fungal, or viral infections, and other non-neoplastic etiologies including collagen diseases. Due to the cytomorphologic overlap of reactive mesothelial cells with malignant cells, general cytologic criteria for diagnosis of malignancy in single cells cannot be applied in most of the effusion specimens. This challenge is further amplified because of surface tension related phenomenon which ‘round up’ the cells after exfoliation in serous fluids. As a result, the native shapes of cancer cells cannot be a guiding feature. Thus the cytomorphologic features of cancer cells in serous fluids may not be same as seen in routine cytopathology of exfoliative, brushing, and fine-needle aspiration specimens.

The cancer cells may continue to proliferate after exfoliation in the nutrient rich effusion fluids and may form proliferation spheres. It is crucial to consider these factors when interpreting effusion cytology. Amongst malignant effusions, adenocarcinomas are the most common cause of metastatic cancers, but almost any type of malignancy including melanomas, hematopoietic neoplasms, sarcomas, and mesotheliomas may involve serous cavities. The interpreter must be aware of the wide range of the cytomorphologic appearances of reactive mesothelial cells in effusion fluids. It is essential to understand these and other nuances related to effusion fluid cytology. Understanding potential pitfalls during various stages from processing to application of ancillary studies would increase the diagnostic accuracy and minimize atypical interpretations and false positivity.

Concordance of Expert Consultation Diagnoses in the Review of Pelvic Washing Specimens

OBJECTIVES

Cytologic specimens are routinely collected as part of gynecologic oncology surgery. Consultation cases often include cytology specimens. Outside diagnosis was compared to consultation diagnosis for cytopathology specimens that were part of larger oncologic cases.

STUDY DESIGN

Gynecologic pathology consultation cases containing pelvic washing (PW) material were queried. Cases had major discordance if the diagnosis changed from negative to positive or vice versa, and minor discordance if an atypical diagnosis was changed to positive or negative or vice versa.

RESULTS

Of 237 cases, 9 showed major discordance (4%), 29 showed minor discordance (12%) and the remaining 199 no discordance (84%). The 9 major discordance cases involved PWs from cases that were performed for ovarian pathology. Treatment would have changed in only 2 of the cases with major discordance. Of the minor discordance cases, 21/29 (72%) involved PW from ovarian cases and 8/29 (28%) were PW from uterine cases.

CONCLUSIONS

Only a few cases showed major or minor discordance, and of those that were discordant, most involved ovarian specimens. Major discordance between original and consulting diagnoses would have changed treatment in only 2 cases.

Abdominopelvic washings: A comprehensive review

Intraperitoneal spread may occur with gynecological epithelial neoplasms, as well as with non-gynecological malignancies, which may result in serosal involvement with or without concomitant effusion. Therefore, washings in patients with abdominopelvic tumors represent important specimens for cytologic examination. They are primarily utilized for staging ovarian cancers, although their role has decreased in staging of endometrial and cervical carcinoma. Abdominopelvic washings can be positive in a variety of pathologic conditions, including benign conditions, borderline neoplastic tumors, locally invasive tumors, or distant metastases. In a subset of cases, washings can be diagnostically challenging due to the presence of co-existing benign cells (e.g., mesothelial hyperplasia, endosalpingiosis, or endometriosis), lesions in which there is only minimal atypia (e.g., serous borderline tumors) or scant atypical cells, and the rarity of specific tumor types (e.g., mesothelioma). Ancillary studies including immunocytochemistry and fluorescence in situ hybridization may be required in difficult cases to resolve the diagnosis. This article provides a comprehensive and contemporary review of abdominopelvic washings in the evaluation of gynecologic and non-gynecologic tumors, including primary peritoneal and mesothelial entities.

Serous and mucinous borderline (low malignant potential) tumors of the ovary

The prognosis for stage I serous borderline ovarian tumors (SBOTs) is thought to be excellent, despite rare, late recurrences. The behavior of advanced-stage SBOTs primarily depends on the invasiveness vs noninvasiveness of associated extraovarian implants. Pelvic and abdominal lymph node involvement and foci of microinvasion do not seem to adversely affect prognosis. Serous tumors with a micropapillary and/or cribriform growth pattern seem to be more frequently bilateral and exophytic and manifest at an advanced stage with a higher incidence of invasive implants than typical SBOTs. Molecular data suggest that such tumors may represent an intermediate stage in the typical SBOT-invasive low-grade serous carcinoma progression. Limited experience with endocervical (müllerian)-type mucinous borderline tumors shows a possible relation to SBOTs in clinicopathologic features and biologic behavior Intestinal-type mucinous borderline ovarian tumors (I-MBOTs) and well-differentiated mucinous carcinomas manifest at stage I in most cases; the prognosis is excellent. Mucinous tumors associated with pseudomyxoma peritonei are almost always secondary to similar tumors of the appendix or other gastrointestinal sites and should not be diagnosed as high-stage I-MBOTs. Rare primary ovarian mucinous tumors associated with pseudomyxoma peritonei are those arising in mature cystic teratomas. Advanced-stage ovarian mucinous carcinomas typically show frank, infiltrative-type invasion; the prognosis is poor.

Ber-EP4 and anti-calretinin antibodies: a useful combination for differential diagnosis of various histological types of ovarian cancer cells and mesothelial cells

The differential diagnosis between reactive mesothelial cells and ovarian carcinoma cells is often difficult in cytologic specimens. Immunocytochemical procedures have been utilized in assisting this differential diagnosis, with limitations. Furthermore, previous studies examined only serous type but not other histological types of ovarian carcinoma cases. Therefore, we evaluated the practical value of various epithelial and mesothelial markers in differential diagnosis of these two types of cells. Various types of ovarian carcinoma (serous, n = 22; mucinous, n = 10; endometrioid, n = 7; clear cell, n = 10) and benign mesothelial tissues (n = 15) were studied by immunohistochemistry. We then studied effective panels of antibodies by immunohistochemistry in 43 cytologic specimens of ascites or peritoneal lavage fluid consisting of 20 reactive mesothelium and 23 adenocarcinomas of the ovary. In the tissue specimens, Ber-EP4, a monoclonal antibody of epithelial antigen, and a polyclonal antibody against calretinin, which is expressed in mesothelium, are used in differentiating reactive mesothelial cells from ovarian carcinoma. In cytologic specimens, the sensitivity and specificity of Ber-EP4 were 100% and 90%, respectively. The sensitivity and specificity of the anti-calretinin antibody were 90% and 91%, respectively. Using multiple regression analysis, the correlation coefficient between epithelial antigen and calretinin reactivity was r = 0.938, with a significance level of p < 0.0001. In conclusion, the combined immunostaining of cytologic specimens for Ber-EP4 and the anti-calretinin antibody is helpful for the differential diagnosis between mesothelial cells and not only serous type, but also mucinous, endometrioid and clear cell types of ovarian cancer cells.

Cytological features of canine ovarian tumours: a retrospective study of 19 cases

The cytological features of 19 histologically confirmed canine ovarian tumours were retrospectively examined. Seven cases were cytologically classified as papillary adenocarcinoma, eight cases as granulosa cell tumours, two cases as mature ovarian teratomas, one case as a dysgerminoma and one case as a mixed granulosa cell tumour/dysgerminoma. On cytology, papillary adenocarcinoma was characterised by a papillary glandular pattern and tight cohesiveness. Granulosa cell tumours showed monolayered clusters of loosely cohesive granulosa cells. Call-Exner-like bodies were found in five of seven cases. Granulosa cells appeared to be heterogeneous and usually contained several intracytoplasmic vacuoles. Teratoma was characterised cytologically by keratin debris (two cases) and a mixture of epithelial cells with sebaceous, basaloid, columnar/palisading or ciliated appearance (one case). The dysgerminoma contained severely atypical round cells admixed with small lymphocytes. The mixed dysgerminoma/granulosa cell tumour had a mixture of germinal and granulosa cells. Cytological diagnosis was in agreement with histopathology in 18 of 19 (94.7 per cent) cases.

Atypical papillary proliferation in gynecologic patients: a study of 32 pelvic washes

Papillary clusters in gynecologic pelvic washes frequently cause diagnostic challenges because they can be associated with borderline or malignant ovarian tumors, as well as benign pelvic diseases. The objective of our study was to review all pelvic washes with atypical papillary proliferation (APP) and investigate whether cytomorphology and/or immunohistochemistry on cell block could determine their origin. Thirty-two pelvic washes from 31 patients containing APP were reviewed and correlated with their corresponding gynecologic or pelvic disease. Previously obtained cell blocks with immunohistochemical (IHC) stains were reviewed also. Nine of 32 washes (28%) were overcalled as malignant and were from patients with 5 borderline serous ovarian tumors (BSTO), 1 ovarian follicular cyst, 1 serous cystadenofibroma, and 1 endometrial carcinoma with ovarian seromucinous cystadenoma. BSTO and endometriosis were the most common sources of APP. Cell blocks could not discriminate further the etiology of APP. Immunohistochemistry was performed rarely and not fully contributory. Caution in interpreting papillary groups and cytohistological correlation is recommended to prevent a high false positive rate.

Pelvic washing cytology in serous borderline tumors of the ovary using ThinPrep®: Are there cytologic clues to detecting tumor cells?

The detection of tumor cells in pelvic washings of patients with serous borderline tumors of the ovary (SBT) remains a diagnostic challenge. Accurate diagnosis of pelvic washings is important in determining therapeutic regimens and assessing patient prognosis. No study has exclusively examined pelvic washing cytology of patients with SBT using only ThinPrep methodology. The purpose of this study is to examine whether cytologic clues exist in detecting tumor cells of SBT in pelvic washings processed with ThinPrep. Using previously established criteria, we reviewed the pelvic washes of 37 patients with SBT and correlated them with the histologic findings in the omentum. We also compared their cytoarchitectural features with pelvic washes in patients with benign ovarian disease and serous carcinoma. Cytoarchitectural features that achieved statistical significance in distinguishing cells of a SBT from reactive mesothelial cells include the following findings: presence of a two-cell population (P = 0.001), psammoma bodies (P = 0.001), cytoplasmic vacuolization (P = 0.001), smooth group contours (P = 0.004), nuclear size >2x neutrophils (P = 0.004), high nuclear-to-cytoplasmic (N/C) ratio (P = 0.004), absent intercellular windows (P = 0.007), and course nuclear chromatin (P = 0.032). Psammoma bodies were the only statistically significant feature distinguishing SBT from serous carcinoma, being more common in SBT than serous carcinoma (P = 0.035). The prominent number of associated psammoma bodies seen in the SBT group was a notable finding that may aid as a valuable cytologic clue in detecting tumor cells. Overall cellularity remains a source of false-negative diagnosis. Correlation with histologic findings remains crucial given our inability to reliably distinguish tumor cells of SBT from endosalpingiosis or serous adenocarcinoma.

Diagnostic pitfalls of peritoneal washing cytology and the role of cell blocks in their diagnosis

Mesothelial cell hyperplasia, collagen balls, endometriosis, and endosalpingiosis are diagnostic pitfalls on peritoneal washing cytology in women who present with gynecologic lesions. Over an 8-month period, the peritoneal washings from 10 patients undergoing gynecologic surgery for presumed malignancy showed unusual cytologic findings, several of which posed diagnostic difficulties. The washings from four patients with ovarian carcinomas were cellular and contained clusters and strips of cells with cytologic atypia mimicking malignancy. Confirmation of their benign mesothelial origin was confirmed on immunohistochemistry utilizing cell block preparations. In two cases of endometrial endometrioid carcinoma, the washings contained several clusters of cells surrounding and/or admixed with a globular substance. Due to their similarity to endometrial cells, immunohistochemistry was performed on cell block preparations. The cells were positive for cytokeratin and negative for carcinoembryonic antigen and B72.3, confirming their mesothelial origin. In one case, clinically presumed to be a malignant mass, the washings contained tight clusters of cells with mild cytologic atypia admixed with hemosiderin-laden macrophages. In conjunction with the cell block findings, a diagnosis of endometriosis was made. Extensive endometriosis was found on the surgically resected specimen. In two cases, strips of ciliated epithelial cells resembling tubal epithelium were present on the cytologic and cell block preparations, consistent with endosalpingiosis. The peritoneal washings in one case contained several clusters and balls of atypical cells surrounding microcalcifications on cell block preparation. Since calcification within groups of cells in peritoneal washings always raised the possibility of malignancy, a serous carcinoma of the ovary, particularly of borderline malignancy, would have to be excluded. Fortunately, the resected specimen was free of tumor and showed calcified endosalpingiosis on the ovarian surface. Preparation of cell blocks from peritoneal washings is of value in the work-up and management of patients who present with cytologic mimickers of malignancy on fluid cytology.

Micropapillary serous carcinoma of the ovary: cytomorphologic characteristics in peritoneal/pelvic washings

BACKGROUND

Micropapillary serous carcinoma (MPSC), a recently described entity, is an ovarian tumor with a distinctive histologic architecture that lacks a destructive infiltrative growth pattern and behaves like a low-grade neoplasm. The purpose of this study was to determine if specific cytomorphologic features were associated with this tumor in peritoneal/ pelvic washings.

METHODS

Eight cases of MPSC were retrieved from the cytopathology files at The Johns Hopkins Hospital. Patients ranged in age from 31 to 74 years (mean, 58 years). A cytomorphologic comparison was made with pelvic washings of eight cases of papillary serous carcinoma (PSC) of the ovary.

RESULTS

MPSC demonstrated small but well formed papillary fragments (generally < 30 cells) composed of monotonous, relatively small epithelial cells, often with multiple nucleoli. Single, large atypical cells were seldom present and were seen in less than one half of cases. Cellularity was generally high and slide background was clear with minimal inflammatory cells. In comparison, PSC, in addition to the smaller papillary fragments, also exhibited larger more complex papillary fragments (generally > 30 cells) composed of pleomorphic, hyperchromatic cells often with single prominent nucleoli. Single, large tumor cells exhibiting eccentric atypical nuclei or multinucleation were present in high concentration in the majority of PSCs. Psammoma bodies were observed in one half of cases in both tumor types.

CONCLUSIONS

Although MPSC shares cytomorphologic similarities with PSC, it can be diagnosed adequately in peritoneal/ pelvic washings. Careful interpretation of the subtle cytologic differences seen in the two tumor types may facilitate the differentiation of these neoplasms for a more appropriate management of the patient.

Cytologic identification of serous neoplasms in peritoneal fluids

BACKGROUND

Recognition of serous neoplasms in peritoneal fluids and their subclassification into serous borderline tumors (SBT) and serous carcinomas (SCA) may be difficult. The objective of this study was to determine whether morphologic criteria can distinguish reactive mesothelial cells (RM), SBT, and SCA (grades 1-3) in peritoneal fluids.

METHODS

A blinded review of 42 peritoneal fluids from 40 patients with histologically confirmed RM (n = 10 patients), SBT (n = 7 patients; 3 with primary ovarian tumors and 4 with primary peritoneal tumors), and SCA (n = 23 patients; 7 with grade 1 tumors, 6 with grade 2 tumors, and 10 with grade 3 tumors; 12 with primary ovarian tumors and 11 with primary peritoneal tumors) evaluated papillae presence and size, intercellular windows, group contours, dyshesion, nuclear atypia, size and overlap, cell size, and nucleoli and nuclear-to-cytoplasmic ratios. From these parameters, specimens were classified as RM, SBT versus grade 1 SCA, or grade 2 SCA versus grade 3 SCA.

RESULTS

RM were identified as groups of small cells with minimal nuclear atypia and overlap, intercellular windows, and irregular group borders without papillae. No features differentiated SBT from grade 1 SCA. Grade 2 and 3 SCA showed more nuclear atypia and overlap with larger nuclei and cells. Thirty-nine of 42 specimens (95%) were correctly identified as RM or serous neoplasm. Two SBT specimens and one grade 1 SCA specimen were overcalled, and three SCA specimens (two grade 2 and one grade 3) were undergraded.

CONCLUSIONS

The distinction of RM from serous neoplasms in peritoneal fluids is possible in most patients by examination of cell group architecture, nuclear atypia, and nuclear size. Differentiation of SBT from grade 1 SCA is not reliable, meriting a differential diagnosis. Most high-grade SCA specimens can be identified by increased nuclear atypia, overlap, and size.