Cytopathology of malignant mesothelioma: a study of its patterns and histological bases

Cytological Diagnostic Procedures in Malignant Mesothelioma

Malignant mesotheliomas (MM) are rare tumors with high mortality rates, whose incidence varies regionally and nationally, and the diagnosis is difficult. Histology-based diagnosis is considered the gold standard despite its low sensitivity of 57-84%. However, recent advances in cytological analysis offer promise for diagnostic advancements. In this study, we reappraised the current cytological guidelines for the MM diagnosis and concluded on their practicability and reliability. The study included 5731 consecutive specimens of pleural effusions from 4552 patients (3026 males of the average age of 67.5 years and 1526 females of the average age of 65.4 years) between December 2017 and January 2000. Out of these patients, 444 (9.8%) were diagnosed with MM. The effusions were examined by immunocytochemistry using routine Giemsa staining. Additionally, hyaluronic acid (HA) was assessed. Cytological findings confirmed 223 out of the 444 MM. The additional 88 cases with negative cytology were corroborated by supplemental assessments of HA above 30 mg/L. Cytological evaluation accomplished the sensitivity of 0.50, specificity of 0.99, and a positive predictive value (PPV) of 0.97 for MM diagnosis. The use of HA determination raised the sensitivity to 0.70 without affecting the specificity or PPV. We conclude that cytological evaluation of effusions aided by the assessment of HA demonstrates the diagnostic sensitivity and specificity for MM no less than the hitherto standard histological evaluation. The cytology-based MM diagnosis may thus be routinely considered when MM is suspected and may offer confirmatory advantages in difficult or doubtful diagnostic cases.

The value of cytology in distinguishing malignant mesothelioma: An institutional experience of 210 cases reclassified according to the International System for Reporting Serous Fluid Cytopathology (ISRSFC)

OBJECTIVE

Malignant mesothelioma (MM) is usually diagnosed by histological examination of tissue samples; however, effusion cytology offers an opportunity to identify a strong possibility for mesothelioma diagnosis at an early stage. We conducted a retrospective analysis of cytological specimens from a large series of histologically proven MM diagnosed over 19 years. The cases were reviewed and reclassified according to the International System for Reporting Serous Fluid Cytopathology (ISRSFC).

METHODS

A total of 450 cases were identified. Cytological analysis was present in 210 patients (164 pleural and 46 peritoneal effusions). All cases were reviewed and reclassified according to the proposed ISRSFC scheme. A comparison among the cytomorphological features was made throughout the different diagnostic categories.

RESULTS

The 210 cases were histologically diagnosed as follows: 192 (91.4%) cases had an epithelioid type and 18 (8.6%) had a sarcomatoid subtype of MM. The cytological cases were reclassified as follows: 2 (0.9%) as non-diagnostic (ND), 81 (38.6%) as negative for malignancy (NFM), 4 (1.9%) as atypia of undetermined significance (AUS), 11 (5.2%) as suspicious for malignancy (SFM), 112 (53.4%) as malignant (MAL). Sarcomatoid cells in the MAL category were characterised cytomorphologically by more pronounced discohesion. In comparison with the epithelioid subtype, the tumour cells appeared solitary with moderate or marked nuclear pleomorphism, and irregular chromatin.

CONCLUSIONS

It is important to recognise the cytological characteristics of this aggressive entity to suggest an early and precise possible diagnosis. Morphological features, coupled with clinico-radiological data may help the clinicians in adequately managing the patients.

Diagnostic Utility of Pleural Fluid Cell Block versus Pleural Biopsy Collected by Flex-Rigid Pleuroscopy for Malignant Pleural Disease: A Single Center Retrospective Analysis

Background

Some trials recently demonstrated the benefit of targeted treatment for malignant disease; therefore, adequate tissues are needed to detect the targeted gene. Pleural biopsy using flex-rigid pleuroscopy and pleural effusion cell block analysis are both useful for diagnosis of malignancy and obtaining adequate samples. The purpose of our study was to compare the diagnostic utility between the two methods among patients with malignant pleural disease with effusion.

Methods

Data from patients who underwent flex-rigid pleuroscopy for diagnosis of pleural effusion suspicious for malignancy at the National Cancer Center Hospital, Japan between April 2011 and June 2014 were retrospectively reviewed. All procedures were performed under local anesthesia. At least 150 mL of pleural fluid was collected by pleuroscopy, followed by pleural biopsies from the abnormal site.

Results

Thirty-five patients who were finally diagnosed as malignant pleural disease were included in this study. Final diagnoses of malignancy were 24 adenocarcinoma, 1 combined adeno-small cell carcinoma, and 7 malignant pleural mesothelioma (MPM), and 3 metastatic breast cancer. The diagnostic yield was significantly higher by pleural biopsy than by cell block [94.2% (33/35) vs. 71.4% (25/35); p = 0.008]. All patients with positive results on cell block also had positive results on pleural biopsy. Eight patients with negative results on cell block had positive results on pleural biopsy (lung adenocarcinoma in 4, sarcomatoid MPM in 3, and metastatic breast cancer in 1). Two patients with negative results on both cell block and pleural biopsy were diagnosed was sarcomatoid MPM by computed tomography-guided needle biopsy and epithelioid MPM by autopsy.

Conclusion

Pleural biopsy using flex-rigid pleuroscopy was efficient in the diagnosis of malignant pleural diseases. Flex-rigid pleuroscopy with pleural biopsy and pleural effusion cell block analysis should be considered as the initial diagnostic approach for malignant pleural diseases presenting with effusion.

Computed tomography-guided cutting needle pleural biopsy: Accuracy and complications

In cases of pleural lesion, tissue samples can be obtained through thoracoscopy or closed needle biopsy for histopathological analysis. Cutting needle biopsy is a relatively recent addition to these techniques. The aim of this study was to evaluate the diagnostic accuracy and safety of computed tomography-guided cutting needle pleural biopsy (CT-CNPB), as well as the associated complications, in patients with pleural lesion. This study was a retrospective analysis of 92 percutaneous CT-CNPBs on 90 patients between March 2008 and May 2013. For group comparisons, χ² tests were used to detect the risk factors for diagnostic accuracy (false-negative rate). Of the 92 CT-CNPBs, malignant lesions were diagnosed in 55 cases (mesothelioma in 12, metastatic pleural disease in 36, synoviosarcoma in one, indeterminate-origin disease in one and false-negative lesion in five) and benign pleural disease was diagnosed in 37 cases (inflammation in 15, tuberculosis in 10, granuloma in three, solitary fibrous tumor in two, hematoma in one, fungus in one and indeterminate-origin disease in five). The sensitivity of diagnostic malignant lesion was 90.9%, and the specificity and positive and negative predictive values were 100, 100 and 88.1%, respectively. The overall diagnostic accuracy was 94.6%. A specific diagnosis was achieved in 89.1% of malignant lesions and 86.4% of benign lesions. Univariate analysis of the risk factors affecting accuracy (false-negative rate) did not reveal any significant differences (all P>0.05). The complication rates were 6.5% for pneumothorax, 8.7% for hemorrhage and 1.1% for hemothorax. In conclusion, CT-CNPB is a safe and accurate diagnostic technique that can be recommended as the primary method of diagnosis in patients with pleural thickening or lesions observed by CT scan.

Usefulness of EMA, GLUT-1, and XIAP for the cytologic diagnosis of malignant mesothelioma in body cavity fluids

We compared the effectiveness of epithelial membrane antigen (EMA) with 2 newly described markers, X-linked inhibitor of apoptosis protein (XIAP) and an isoform of glucose transporter (GLUT-1), in the distinction between malignant mesothelioma (MM) and benign effusion (BE) in body cavity fluids. Immunohistochemical studies were performed on cell block sections from 35 cases of histologically confirmed MM and 38 BEs, using antibodies to EMA, XIAP, GLUT-1 (GLUT-1m, monoclonal; GLUT-1p, polyclonal). Results were graded based on the percentage of cells staining: negative (0%), 1+ (<25%), 2+ (25%-49%), 3+ (50%-74%), and 4+ (75%-100%). The performance of each marker was compared using receiver operating characteristic curve analysis. EMA demonstrated the best accuracy, with an area under the curve of 0.91 as compared with XIAP (0.67), GLUT-1m (0.74), and GLUT-1p (0.80). Based on these findings, EMA is a better marker than XIAP or GLUT-1 for the diagnosis of MM.

Cytopathologic differential diagnosis of malignant mesothelioma, adenocarcinoma and reactive mesothelial cells: A logistic regression analysis

Distinguishing malignant mesothelioma, adenocarcinoma and reactive mesothelial proliferation in both cytologic and surgical pathologic specimens is often a diagnostic challenge. Conventional cytomorphologic assessment is an important step in the differential diagnosis of these entities.The pleural effusion cytologies from 40 cases of malignant mesothelioma, 40 cases of adenocarcinoma and 30 cases of reactive mesothelial proliferation diagnosed between 1997 and 2007 were reviewed. Twenty-seven cytologic features which are regarded as useful in the differential diagnosis of mesothelioma, adenocarcinoma and benign mesothelial proliferation were assessed. These cytologic features were subjected to a stepwise logistic regression analysis. Three features were selected to distinguish malignant mesothelioma from adenocarcinoma: giant atypical mesothelial cell (P = 0.0001), nuclear pleomorphism (P = 0.0001) and acinar structures (P = 0.0001), the latter two being characteristics of adenocarcinoma. The variables selected to differentiate malignant mesothelioma from reactive mesothelial cells were: cell ball formation (P = 0.0001), cell in cell engulfment (P = 0.0001) and monolayer cell groups (P = 0.0001), the latter being a feature of benign mesothelial proliferation. When these selected variables were subjected to a stepwise logistic regression analysis, the logistic model correctly predicted 90% of cases of benign mesothelial proliferation versus 97.5% of malignant mesothelioma and 92.5% of malignant mesothelioma versus 92.5% of adenocarcinoma.Conventional cytomorphologic assessment is the first step to establish an accurate diagnosis in pleural effusions. Several cytologic features have predictive value to separate malignant mesothelioma from adenocarcinoma and reactive mesothelial proliferation.

Accuracy and reproducibility of pleural effusion cytology

The increasing number of Malignant Mesothelioma (MM) cases that arrive for expert examinations to court for compensation reasons in subjects exposed to asbestos, in many instances rely exclusively on cytological smears of pleural effusion. We evaluated the accuracy and reproducibility of cytological pleural effusions, based on morphological criteria alone. Nine pathologists and eight residents from seven institutions in north-east Italy blindly examined 45 smears of MM (17), metastases (14) and benign effusions (14), in two rounds. Diagnoses had been confirmed by immunohistochemical and clinical follow-up, and eventually at autopsy. Diagnostic accuracy, interobserver and intraobserver agreement in the distinction of benign vs malignant cases, and in the differentiation of primary from metastatic malignancies, were evaluated. The distinction of benign from malignant smears resulted rather satisfactory (k=0.514), but markedly decreased in differentiation of MM from metastases (overall agreement: k=0.343), as well as when readings from residents were analyzed (k=0.132). Cytology is a useful and reliable tool in the identification of malignancies, but when the distinction of primary from metastatic tumors is addressed morphological criteria alone are not sufficient for a definite diagnosis of MM and the use of cell blocks, immunohistochemistry (IHC) and molecular ancillary techniques are recommended.

The value of ThinPrep and cytospin preparation in pleural effusion cytological diagnosis of mesothelioma and adenocarcinoma

The diagnosis of malignant mesothelioma requires an integration of the clinical presentation, radiological studies, and immunohistochemical stain of histological sections. Cytological diagnosis on pleural effusions of mesothelioma and pulmonary adenocarcinoma is highly desirable but debatable. A spectrum of cytological features has been found to be associated more commonly with malignant mesothelioma (e.g., peripheral cytoplasmic skirt, bubbly cytoplasm, cyanophilic cytoplasm, and scalloped border of cell balls) vs. adenocarcinoma (e.g., two-cell population, inspissated cytoplasmic material, cytoplasmic vacuole, angulated and indented nuclei, and smooth border of cell balls) to only name a few. The current study is designed to assess whether the introduction of a liquid-based technology such as ThinPrep (TP) can provide additional diagnostic value in addition to the conventional cytospin Diff-Quik (DQ) preparations. Pleural effusion specimens were prepared with split samples for DQ-stained cytospin and Papanicolaou-stained liquid-based TP. Fifteen pleural effusion samples with immunohistologically confirmed malignant mesothelioma and 13 pleural effusion samples of immunohistologically confirmed pulmonary adenocarcinomas were retrieved from our files. Both DQ cytospin- and Papanicolaou-stained TP slides were evaluated for the known cytological features associated with malignant mesothelioma (25 cytological features) and adenocarcinoma (22 cytological features) without knowledge of the original cytological and histological diagnoses. The McNemar test was used to compare these two cytological preparations for both malignant mesothelioma and pulmonary adenocarcinoma. In the malignant mesothelioma group, 4 of 25 cytological features evaluated, bubbly cytoplasm (P = 0.002), vacuolated cytoplasm (P = 0.005), cell-in-cell arrangement (P = 0.007) and irregular nuclear contour (P = 0.083), were seen more frequently in the DQ cytospin preparation, as opposed to only one feature, nuclear size enlargement (P = 0.008), more readily seen using TP. In the pulmonary adenocarcinoma group, only 1 of 22 cytological features evaluated, presence of angulated or indented nuclei (P = 0.025), was seen more frequently in DQ as opposed to two features, presence of two- cell population (P = 0.04) and presence of micropapillary structures (P = 0.1), were seen more readily in TP. All other cytological features evaluated distinguishing mesotheliomas (20 features) and pleural adenocarcinomas (19 features) were seen equally readily in both types of specimen preparation techniques. This study suggests that the liquid-based TP preparation of pleural effusions does not appear to provide additional diagnostic value when compared with the DQ cytospin preparation in the cytological distinction between mesothelioma and adenocarcinoma in pleural effusions. Most cytological features evaluated, 20 of 25 (mesothelioma) and 19 of 22 (adenocarcinoma), can be seen in both preparation techniques.

The value of epithelial membrane antigen expression in separating benign mesothelial proliferation from malignant mesothelioma: A comparative study

Differentiating reactive mesothelial (RM) proliferation from malignant mesothelioma (MM) can be cytologically challenging. There have been discordant studies reporting the value of epithelial membrane antigen (EMA) in differentiating RM from MM. In this study, we investigated the expression of two different clones of EMA in RM and MM. Twenty cases of pleural effusion smears of RM and 20 cases of MM with their corresponding cell blocks were retrieved from the hospital computer system. Diagnosis of MM was confirmed by surgical decortication or pneumonectomy with immunostaining studies and/or electron microscopy. Cases of RM were confirmed by clinical history and histology. Cell blocks were formalin-fixed, paraffin-embedded, and immunostained for EMA clone Mc5 and EMA clone E29. The positive rates for clone Mc5 were 14/20 (70%) for MM and 12/20 (60%) for RM and EMA clone E29 were 15/20 (75%) for MM and 0/20 (0%) for RM. The sensitivity and specificity for EMA clone Mc5 were 70 and 40%, respectively. For EMA clone E29, the sensitivity and specificity were 75 and 100%, respectively. In conclusion, both RM and MM immunostained for EMA clone Mc5, indicating that it is not a reliable immunocytochemical marker for differentiating RM from MM. EMA clone E29 was negative in all cases of RM and positive in 75% of MM and therefore is a reliable immunocytochemical marker for differentiating RM from MM.

Malignant pleural mesothelioma: evaluation with CT, MR imaging, and PET

Imaging plays an essential role in the evaluation of malignant pleural mesothelioma (MPM). Computed tomography is the primary imaging modality used for the diagnosis and staging of MPM. Magnetic resonance (MR) imaging and, more recently, positron emission tomography (PET) have emerged as modalities that can provide additional important diagnostic and prognostic information to help further delineate the extent of disease, especially in surgical candidates. Use of MR imaging performed with different pulse sequences and gadolinium-based contrast material can improve the detection of tumor extension, especially to the chest wall and diaphragm. PET can provide both anatomic and metabolic information, especially in cases of extrathoracic and mediastinal nodal metastasis. Each imaging modality has its advantages and limitations, but their combined use is crucial in determining the most appropriate treatment options for patients with MPM.

Cytomorphology of metastatic mesothelioma in fine-needle aspiration specimens

The morphologic features of mesothelioma occurring in serous fluids, as well as fine-needle aspiration (FNA) of primary tumors, have been extensively described. Descriptions of the FNA findings in metastatic lesions of mesothelioma, however, are limited to single cases. In this report, we illustrate the cytomorphologic features of four cases of metastatic mesothelioma which underwent FNA, and one additional cytologic preparation taken from a surgically-excised metastatic lesion. The cytomorphologic features of metastatic mesothelioma varied greatly among individual cases with respect to the degree of nuclear pleomorphism, amount of cytoplasm, and degree of cellular cohesion. However, one feature which was consistently seen was the presence of numerous distinct, uniformly small intracytoplasmic vacuoles, believed to represent intracellular fat and glycogen. These morphologic features are illustrated, and the differential diagnosis of intracytoplasmic vacuoles within epithelioid tumor cells in primary and metastatic lesions is discussed.

Confocal laser scanning microscopy and three-dimensional reconstruction of cell clusters in serous fluids

Thick cell clusters are a common finding in reactive and malignant effusions. In order to arrive at a diagnosis, clusters are evaluated for certain cytomorphologic features including size, shape, smooth vs. scalloped borders, and three-dimensional (3-D) configuration. By conventional microscopy, the image of these clusters is often blurred due to limitations in resolution. Consequently, the exact internal structure and cellular arrangement within these clusters cannot be adequately determined. Utilizing confocal laser scanning microscopy (CLSM), we examined serous fluids from a variety of conditions. Cases included mesothelioma, adenocarcinoma, and papillary adenocarcinoma. Smears were stained with 0.01% ethidium bromide and 1% eosin Y, followed by analysis with an ACAS 570 image analyzer (Meridian Instruments, Inc. Okemos, MI). Serial confocal fluorescence images were acquired, which allowed 3-D reconstruction of the clusters. Mesothelioma clusters (excluding those with obvious central collagen cores by light microscopy) appeared to be formed of the following configurations: 1) randomly coiled cords of cells, 2) small papillae encompassing central cores, and 3) tissue fragments with pseudoacinar formation. In contrast, adenocarcinomas had a more orderly pattern, with tightly cohesive cells and true acinar formation.