Cytopathology of malignant mesothelioma: a stepwise logistic regression analysis.

Twenty-four cytologic features, previously reported to be useful in the distinction of malignant mesothelioma, adenocarcinoma, and benign mesothelial proliferation in serous effusions were assessed. Forty-four cases of malignant mesotheliomas, 46 cases of metastatic adenocarcinomas, and 30 cases of benign mesothelial proliferations were examined for these parameters. When these cytologic features were subjected to a stepwise logistic regression analysis, five features were selected to distinguish malignant mesothelioma from adenocarcinoma. These were true papillary aggregates, multinucleation with atypia, cell-to-cell apposition, acinus-like structures, and balloon-like vacuolation, the latter two features being characteristic of adenocarcinoma. The four variables selected to distinguish malignant mesothelioma from benign mesothelial proliferations were nuclear pleomorphism, macronucleoli, cell-in-cell engulfment, and monolayer cell groups, the latter being a feature of benign proliferations. Using these selected variables, the logistic model correctly predicted 95.4% of cases of malignant mesothelioma versus 100% of adenocarcinoma and 100% of malignant mesotheliomas versus 90% of benign mesothelial proliferations. The results of regression analysis suggest that many of the previously described cytologic features are not important diagnostic discriminators.     

Assessment of cell cycle state may facilitate the histopathological diagnosis of malignant mesothelioma

AIMS: The differentiation of benign pleural conditions from malignant mesothelioma may be difficult, especially with a small biopsy. We have tested the hypothesis that assessment of the cell cycle status is of value in the histopathological diagnosis of such biopsies, by comparing 33 malignant mesotheliomas with 36 cases of reactive mesothelial hyperplasia and reactive pleural fibrosis. METHODS AND RESULTS: Biopsies were investigated for proliferative status by immunostaining for a novel antibody, MCM2, all of which showed nuclear expression of MCM2 at higher frequency than Ki67 (P < 0.0001). Counts in areas of maximum tumour staining showed significantly higher labelling indices (LIMax) in epithelioid and sarcomatoid mesotheliomas compared with reactive mesothelial hyperplasia and reactive pleural fibrosis (P < 0.0001 for both). Average counts (LIAve) revealed a significant increase in epithelioid mesothelioma compared with reactive mesothelial hyperplasia (P < 0.0001). CONCLUSION: We consider MCM2 to be a useful adjunct in the differential diagnosis of malignant mesothelioma.     

心包原发性恶性间皮瘤的临床病理分析

目的：探讨心包原发性恶性间皮瘤的临床病理特征。诊断与鉴别诊断要点。方法：对4例心包原发性恶性间皮瘤进行临床病理分析。光镜及免疫组化染色观察并复习有关文献。结果：男3例,女1例,平均年龄42岁,3例呈局限型,1例为弥漫浸润型。组织学上可表现为肉瘤样梭形细胞型,上皮样型及双相型,免疫组化染色显示肉瘤样梭形细胞表CK、vimentin;上皮样型瘤细胞表达HBME1、CK。结论：原发于心包的恶性间皮瘤罕见,预后极差。临床常被误诊,其组织形态亦复杂多样,应注意与心包的良性增生性病变,心包转移性腺癌和梭形细胞肿瘤等相鉴别。     

Immunocytochemical panel for the identification of malignant cells in serous effusions.

The cytologic diagnosis of malignancy in serous effusions can be challenging. An immunocytochemical (ICC) panel using commercially available antibodies (to carcinoembryonic antigen [CEA], epithelial membrane antigen [EMA], B72.3, Leu-M1, cytokeratin [CK], leukocyte common antigen [LCA], S-100 protein, and vimentin) was applied to cell blocks fixed in methyl Carnoy's solution that were from 55 consecutive pleural, peritoneal, and pericardial fluid specimens. The results were correlated with data from clinical records and routine cytologic studies. Final cytologic diagnoses included 26 of adenocarcinoma and 1 of mesothelioma. The remaining 28 cases were considered to be benign (reactive) proliferations. EMA, CEA, B72.3, and Leu-M1 were present in 96%, 77%, 58%, and 42% of adenocarcinomas, respectively. These determinants were absent in the mesothelioma and the reactive effusions, although anti-CEA yielded strong background staining of inflammatory cells. The CK markers identified malignant cells in 93% of cases, but consistently stained mesothelial cells as well. Antivimentin strongly labeled mesothelial cells in all cases, with weak to absent staining of malignant cells. In 3 of 26 carcinoma cases (12%), the ICC panel identified malignant cells that were not recognized initially on routine cytologic examination. In 1 of 26 cases (4%), the panel was falsely negative. Use of this approach can improve the diagnostic accuracy of cytologic examination of serous fluids. The ICC panel is especially helpful when atypical mesothelial proliferation is present, or in cases that are clinically suspect for malignancy, but cytologically negative because there are only a few malignant cells, or those that are cytologically bland.     

Malignant mesothelioma: cytologic diagnosis with histologic, immunohistochemical, and ultrastructural correlation.

The differential diagnoses of malignant mesothelioma in serous effusions include adenocarcinoma and reactive mesothelial cells. While several cytologic features are of predictive value in separating these entities, immunostaining and ultrastructural examination are important adjuncts that increase the diagnostic yield. Many of the cytomorphologic features can be correlated with immunohistochemical and ultrastructural findings. Most important among these is the ultrastructural demonstration of long, often branching microvillous processes in malignant mesothelial cells. Corresponding microvilli can be visualized by immunostaining for epithelial membrane antigen in both cell block preparations from effusions and biopsy specimens, allowing the identification of malignant mesothelioma. In addition, the circumferential distribution of these immunostained microvilli in cells dispersed in stromal connective tissue identifies them as malignant mesothelial cells, corresponding to the ultrastructural appearance of aberrant microvilli, which project through deficiencies in the basal lamina. These microvilli show interdigitation with stromal collagen fibers, a phenomena not observed in adenocarcinoma.     

Osteosarcoma pleural effusion: A diagnostic challenge with some cytologic hints

Pleural effusions can be the first manifestation, recurrence, or metastasis of small round cell sarcomas in children. The most common are Ewing sarcoma, neuroblastoma, and rhabdomyosarcoma. The cytomorphology is variable, the cells can be cohesive, single cells, small or large, morphologically mimicking lymphomas, carcinomas, melanomas, and mesothelioma depending on the sarcoma involved. Osteosarcomas are rare. Their rarity, variable histomorphologic features, immunophenotypic heterogeneity, being of osseous or extraosseous origin and focality of malignant osteoid matrix make their cytologic recognition a diagnostic challenge. They can be confused with small round cell sarcomas, may be misinterpreted as degenerative inflammatory cells, or masked by florid reactive mesothelial hyperplasia particularly in pleural effusions. However, attention to certain cytomorphologic features in smears and cellblock sections should raise suspicion. We report a case of a 9‐year‐old child who presented with cough, chest pain and breathing difficulty, left pleural effusion, a collapsed consolidated lower lung lobe, and a clinical impression of pneumonia. Pleural fluid cytology was initially reported as inflammatory effusion with florid reactive mesothelial hyperplasia. Tissue biopsy of the lung mass showed histomorphologic features consistent with osteosarcoma. A careful look at the cytology materials and cellblock sections showed helpful cytomorphologic features that were masked by florid reactive mesothelial cells and misinterpreted as degenerative inflammatory lymphocytes. An extracellular matrix was a helpful hint. Malignant pleural effusion secondary to osteosarcoma is rare. Cytologic examination may help reach the correct diagnosis if the smears and cellblock sections are carefully evaluated for certain helpful cytomorphologic features, particularly osteoid matrix.     

Malignant mesothelioma eight years after a diagnosis of atypical mesothelial hyperplasia

The separation of mesothelial hyperplasia from early malignant mesothelioma remains one of the most difficult problems in histopathology. Inconclusive cases are termed "atypical mesothelial hyperplasia" and treated expectantly. A 49 year old male pipeline engineer was diagnosed as having atypical mesothelial hyperplasia in appendiceal serosa by the US-Canadian Mesothelioma Panel. Eight years later, he developed overtly malignant peritoneal and pleural mesothelioma. In hindsight, histological similarities between the diffuse malignant mesothelioma and the atypical mesothelial proliferation suggested malignancy from the outset. The most important of these features were the degree of mesothelial proliferation, micronodularity, architectural complexity, superficial invasion, uniform mild cytological atypia, and the absence of a clinical cause for a benign mesothelial proliferation. Ancillary investigations including immunohistochemistry were of no benefit in determining whether the atypical mesothelial hyperplasia was benign or malignant. Careful histological examination remains the mainstay of the diagnosis of early mesothelioma.     

Malignant mesothelioma with prominent adenomatoid features: a clinicopathologic and immunohistochemical study of 10 cases

The clinicopathologic and immunohistochemical features of 10 cases of pleural malignant mesothelioma with predominantly adenomatoid growth pattern are described to determine the clinical, histologic, and behavioral features of these tumors and to highlight the importance of separating this unusual pattern from the benign adenomatoid tumor. Seventy-seven cases of pleural biopsy and extrapleural pneumonectomy specimens for malignant mesothelioma were examined to identify the specific type of histologic growth pattern exhibited by the tumors. The 10 cases herein described were identified as an unusual histopathologic subset of these tumors. Nine patients were men and one was a woman with an age range of 56 to 82 years (mean, 68.5 years). The main presenting symptoms included cough, dyspnea, and chest pain. The typical features of pleural malignant mesothelioma were noted both radiologically and macroscopically. The tumors were characterized by diffuse pleural thickening with confluent nodular patches of tumor obliterating the pleural space. Histologically, a distinct morphology was observed composed of small tubular spaces lined by epithelioid cells, reminiscent of adenomatoid tumors of the genital tract. Immunohistochemical studies confirmed the mesothelial nature of the tumors. Clinical follow-up in 7 of 7 patients demonstrated a mean survival of 10 months from time of diagnosis. Adenomatoid mesothelioma is an unusual variant of epithelioid malignant mesothelioma that histologically may mimic a range of other tumors, including benign adenomatoid tumors and metastases of adenocarcinoma to the pleura. The clinical presentation, infiltrative growth, distinct histologic features, cytologic atypia and immunohistochemical profile all serve to differentiate adenomatoid malignant mesothelioma from other infiltrative processes involving the pleura.     

Malignant mesothelioma: immunohistochemistry and DNA ploidy analysis as methods to differentiate mesothelioma from benign reactive mesothelial cell proliferation and adenocarcinoma in pleural and peritoneal effusions

OBJECTIVE: To determine whether malignant mesotheliomas can be differentiated from adenocarcinomas and benign reactive mesothelial cells in pleural and peritoneal fluids using immunohistochemical analysis in conjunction with DNA ploidy analysis. DESIGN: Sixteen cases of malignant mesothelioma, including epithelial, sarcomatous, and biphasic types, were collected. DNA analysis using flow cytometry and/or image analysis was performed on paraffin-embedded tissue from 15 of the mesothelioma cases, as well as on cytospin cell preparations from samples of pleural and peritoneal fluids from cases with either cytologically proven adenocarcinoma (seven cases) or benign reactive mesothelial cells (seven cases). Immunohistochemical studies were done in 15 mesotheliomas, 5 adenocarcinomas, and 4 benign reactive mesothelial cell effusions. RESULTS: All malignant mesotheliomas tested (100%) stained positively for prekeratin, whereas stains for carcinoembryonic antigen, B72.3, Leu-M1, and Ber-EP4 were negative. Stains vimentin, epithelial membrane antigen, and CA125 were positive in 75%, 75%, and 25% of cases tested, respectively. Benign reactive mesothelial cell cases stained similarly. Adenocarcinomas were more likely to react positively with B72.3, Ber-EP4, and carcinoembryonic antigen, and negatively with vimentin. DNA analysis showed that all benign cases were diploid, while all adenocarcinomas were nondiploid. Fifty-three percent of the malignant mesotheliomas were nondiploid. Sensitivity for detection of nondiploidy was greater for image analysis than for flow cytometry (100% vs 75%). CONCLUSIONS: B72.3, Ber-EP4, carcinoembryonic antigen, and vimentin are useful immunohistochemical markers in differentiating malignant mesotheliomas from adenocarcinomas, whereas immunohistochemistry does not reliably distinguish malignant from benign hyperplastic mesothelial cells. The addition of DNA ploidy studies is useful for differentiating the latter two groups.     

The diagnosis of malignancy in effusion cytology: a pattern recognition approach

This review presents a pattern recognition approach for the diagnosis of malignant effusions. The cytomorphologic features of reactive mesothelial proliferation, mesothelioma and metastatic carcinoma are presented. In addition, the role of ancillary studies in challenging cases and the importance of integrating clinical findings are stressed. An algorithmic approach to the workup of serous effusions as well as pitfalls for false-positive diagnosis are discussed.     

Atypical mesothelial hyperplasia associated with bronchogenic carcinoma.

Atypical mesothelial hyperplasia encountered in pleural fluid or in a pleural biopsy specimen raises the suspicion that one may be dealing with a diffuse malignant mesothelioma of the pleura. We studied eight cases with cytologic or histologic changes of mesothelial atypia thought to be suspicious for diffuse malignant mesothelioma. In each case, the hyperplasia was associated with a bronchogenic carcinoma in the lung subjacent to the mesothelial hyperplasia. Bronchogenic carcinoma should be added to the list of causes of atypical mesothelial hyperplasia. This combination of reactive and malignant processes should be appreciated, since pleural carcinomatosis and diffuse malignant mesothelioma must be separated for clinical and epidemiologic reasons.     

Diagnostic utility of D2-40 and podoplanin in effusion cell blocks

The distinction between malignant mesothelioma and adenocarcinoma is a diagnostic challenge in cytologic specimens of effusion fluids. As for today, no single antibody has demonstrated absolute sensitivity or specificity for Mesothelioma. D2-40 and podoplanin have recently been recognized to stain mesothelial cells. Our aim for this study was to evaluate the utility of these two markers as indicators of mesothelial cells using cell blocks by comparison with two other established mesothelial markers. A total of 40 cell blocks of effusion fluids including cases of epithelioid mesotheliomas, metastatic carcinomas and benign cases with reactive mesothelial cells were selected. A panel of immunostains including D2-40, podoplanin, CK5, and calretinin was performed. D2-40 and podoplanin were positive in 100% of mesothelioma cases in comparison to metastatic adenocarcinoma cases where the positivity was 0%. It is concluded that D2-40 and podoplanin are very useful markers for mesotheliomas. Since these markers are extremely helpful in differentiating epithelioid mesothelioma from metastatic adenocarcinoma, they shall be a valuable addition to the battery of markers used to differentiate the two entities.     

Cytology, immunopathology and flow cytometry in the diagnosis of pleural and peritoneal effusions

There were 106 pleural and peritoneal effusions studied in order to investigate the contribution of immunocytochemistry and flow cytometry to routine cytologic diagnosis. A panel of antibodies (to cytokeratin, vimentin, human milk fat globule, epithelial membrane antigen and carcinoembryonic antigen) was applied to aceton-fixed slides, using immunoperoxydase and immunofluorescence methods. Flow cytometry was performed using a double labeling method, i.e., propidium iodide for DNA staining and keratin for labeling of epithelial cells. In this way DNA aneuploidy was more evident in the histograms when the fluid contained many reactive nonepithelial cells (lymphocytes). A designation of marker profiles was made for the three most frequently occurring diagnoses, i.e., reactive mesothelial proliferation (I), adenocarcinoma (II), and malignant mesothelioma (III). For the differentiation between adenocarcinoma and malignant mesothelioma, carcinoembryonic antigen was the most useful marker as 75% of the adenocarcinomas was carcinoembryonic antigen-positive and the malignant mesotheliomas were consistently negative. Furthermore, evident DNA-aneuploidy strongly supported the diagnosis of adenocarcinoma, as most malignant mesotheliomas were DNA-euploid, even though occasional DNA-aneuploidy was found in malignant mesotheliomas when different effusions from the same patient were examined. For the differentiation between reactive mesothelial cells and malignant mesothelioma human milk fat globule and/or epithelial membrane antigen, in this study proved to be most reliable, their presence strongly indicating malignancy. It is stressed that the method used (fixation, antibodies, washing procedures) can influence these findings. In 16 patients (17%) performing immunopathology and/or flow cytometry meant an important contribution to diagnosis.     

Benign pleural lesions and malignant mesothelioma

Summary In a series of eighteen diffuse malignant mesotheliomas, five cases were encountered in which thoracic surgery with benign nontumorous diagnosis preceded the development of a malignant mesothelioma by several years. The morphological findings in three of these five cases are compared with the morphology of the tumor specimens and an attempt is made to recognize the earliest possible malignant features. Crowding of mesothelial cells, their variability in size and nuclear hyperchromatism are pointed out as warning signs.In relation to these findings, the histogenetic significance of predominantly fibroproliferative versus epithelial-like pleural lesions is discussed. A histogenetic classification, based on the studies of eighteen diffuse malignant mesotheliomas, two benign fibrous mesotheliomas, one pleural fibrosarcoma, and numerous pleural plaques as well as reactive mesothelial lesions, is offered. The therapeutic aspects are mentioned.     

Malignant mesothelioma cells in sputum

In five patients with malignant mesothelioma of pleura, malignant cells, presumably derived from intrapulmonary deposits, were found in sputum specimens. The cells presented mainly as papillary aggregates of epithelial-like cells, in most cases without specific identifiable mesothelial cell features. In one patient, the specimen was received early in the diagnostic work-up and led to a strong consideration of the diagnosis of adenocarcinoma. In the remainder, the finding was incidental, occurring after the diagnosis of mesothelioma had been established. The cases are reported to draw attention to this phenomenon, previously unreported in the cytologic literature, and to emphasize that the finding of malignant cells in sputum does not preclude the diagnosis of malignant mesothelioma.     

Cytopathologic differential diagnosis of low‐grade urothelial carcinoma and reactive urothelial proliferation in bladder washings: a logistic regression analysis

Conventional cytomorphologic assessment is the first step to establish an accurate diagnosis in urinary cytology. In cytologic preparations, the separation of low‐grade urothelial carcinoma (LGUC) from reactive urothelial proliferation (RUP) can be exceedingly difficult. The bladder washing cytologies of 32 LGUC and 29 RUP were reviewed. The cytologic slides were examined for the presence or absence of the 28 cytologic features. The cytologic criteria showing statistical significance in LGUC were increased numbers of monotonous single (non‐umbrella) cells, three‐dimensional cellular papillary clusters without fibrovascular cores, irregular bordered clusters, atypical single cells, irregular nuclear overlap, cytoplasmic homogeneity, increased N/C ratio, pleomorphism, nuclear border irregularity, nuclear eccentricity, elongated nuclei, and hyperchromasia (p ? 0.05), and the cytologic criteria showing statistical significance in RUP were inflammatory background, mixture of small and large urothelial cells, loose monolayer aggregates, and vacuolated cytoplasm (p ? 0.05). When these variables were subjected to a stepwise logistic regression analysis, four features were selected to distinguish LGUC from RUP: increased numbers of monotonous single (non‐umbrella) cells, increased nuclear cytoplasmic ratio, hyperchromasia, and presence of small and large urothelial cells (p = 0.0001). By this logistic model of the 32 cases with proven LGUC, the stepwise logistic regression analysis correctly predicted 31 (96.9%) patients with this diagnosis, and of the 29 patients with RUP, the logistic model correctly predicted 26 (89.7%) patients as having this disease. There are several cytologic features to separate LGUC from RUP. Stepwise logistic regression analysis is a valuable tool for determining the most useful cytologic criteria to distinguish these entities.     

Malignant biphasic pleural mesothelioma metastatic to the liver diagnosed by fine-needle aspiration

As malignant pleural mesotheliomas are most often rapidly fatal, distant metastases are rarely detected. Here, we report a unique case in which the diagnosis of metastatic pleural mesothelioma was made via cytologic examination of a fine-needle aspiration (FNA) of the liver. Recognition of the cytomorphologic features inherent to mesothelioma cells on FNA material may become important for proper patient management. To the best of our knowledge, the diagnosis of malignant pleural mesothelioma metastatic to the liver made by FNA has not been previously documented.     

Acute monoblastic myeloid leukemic pleural effusion: Pitfalls and clues

Acute myeloid leukemic pleural effusions are uncommon with heterogenous cytomorphology and variable immunoprofiles. This imposes a difficult cytologic diagnosis. In particular, acute myeloid leukemia of monocyte lineage mimicking benign and malignant lymphoid and non-lymphoid lesions is challenging. Few cases of acute myeloid monocyte-lineage leukemia have been reported. Our aim is to report a case of a 54-year-old female patient who presented with pancytopenia and bilateral pleural effusions. We highlight the characteristic cytomorphologic features, diagnostic pitfalls and helpful hints of acute monoblastic leukemia. Initially, the cells were misinterpreted as chronic inflammatory histiocytic infiltrates with reactive mesothelial cells. The presence of frequent mitotic figures, apoptotic bodies and a two-cell population raised the possibility of neoplastic cells. The cellular infiltrate simulated lymphoma, carcinoma and melanoma tumor cells. Cellblock immunocytochemistry however showed negative B-cell, T-cell, myeloid, Langerhans cell, plasma cell and dendritic cell lineage markers. They were positive for LCA, CD68, CD4 and CD117 with a high Ki67 index. The cytologically suggested impression of acute myeloid leukemia of monocyte origin favoring monoblastic variant was confirmed by flow cytometry and bone marrow trephine biopsy. Cytomorphologic clues included agranular amphophilic cytoplasm, occasional grooved indented nuclei, tingible body macrophages, associated plasma cells and absent granulocytes. The cytologic and cellblock findings matched the bone marrow trephine biopsy features. Cytopathologists should be aware of this unusual and challenging cytologic diagnosis in patients with pancytopenia and utilize at least two monocyte markers when formulating their differential diagnosis. Certain cytomorphologic features are helpful hints for their correct recognition.     

My approach to the diagnosis of mesothelial lesions

Mesothelial lesions pose considerable diagnostic challenges not only because benign tumours, reactive proliferations and malignant mesothelioma can mimic one another, but also because the morphological patterns displayed by malignant mesothelioma can simulate a variety of epithelial and non-epithelial malignancies. Immunohistochemical markers can aid in distinguishing epithelioid malignant mesothelioma from metastatic adenocarcinoma, but because no single marker reliably separates all cases, a panel of stains is recommended. Immunohistochemical studies are of more limited value in sarcomatoid malignant mesothelioma, and other features often play an essential role. The separation of reactive mesothelial proliferations from malignant mesothelioma on small biopsy can be quite difficult, as distinguishing features, such as stromal invasion, often cannot be adequately assessed. In adequately sampled lesions, however, the distinction between malignant mesothelioma, benign mesothelial proliferations and other tumours can be achieved in most cases by using a carefully integrated approach that incorporates clinical and radiographic data, immunohistochemical studies and, in selected cases, histochemical and ultrastructural techniques.