A comparative evaluation of immunohistochemical markers for the differential diagnosis of malignant pleural tumours

Pleural Mesothelioma: Current Practice and Approach

Pleural mesotheliomas represent one of the most common diagnostic challenges in thoracic pathology. The diagnosis of pleural mesothelioma weighs heavily on clinical and radiologic information. In addition, in the past, before the era of immunohistochemistry, the diagnosis was aided with the use of special histochemical stains-PAS, D-PAS, and mucicarmine, which now very much have been replaced by immunohistochemical stains. In the era of immunohistochemistry, a combination of carcinomatous epitopes and positive mesothelioma markers has become paramount in the diagnosis of mesothelioma, and more recently the use of molecular techniques has become another ancillary tool in supporting such a diagnosis. At the same time, the treatment and clinical outcome of these patients may in some measure be determined by the histopathological features of the tumor and one that also over the years has changed from a palliative type to surgery, chemotherapy, radiotherapy, or a combination of these types. The histopathological growth patterns of mesothelioma are also wide, and in some cases may mimic other tumors that may be primary or metastatic to the pleura. Therefore, the assessment of the diagnosis of mesothelioma is one that requires a global view of the different factors including clinical, radiologic, pathologic-including immunohistochemistry and molecular diagnosis.

Utility of BerEp4/calretinin and desmin/epithelial membrane antigen (EMA) dual immunocytochemical staining in effusion cytology

BACKGROUND

Pleural mesothelioma (PM) is typically diagnosed late during the disease. Earlier detection can increase the chance of effective therapy. Recurrent pleural effusions are the earliest symptoms displaying an array of cytomorphological changes from reactive atypia to malignancy. Diagnosis is possible on effusion cytology by applying molecular and immunocytochemical markers, the main difficulty being when to suspect PM and to differentiate PM from metastatic adenocarcinoma and reactive mesothelial proliferations.

METHODS

We evaluated the diagnostic performance of two immunocytochemical dual stains (BerEp4/Calretinin and Desmin/Epithelial Membrane Antigen (EMA)) on 149 ethanol-fixed cytospin preparation as an initial step to solve the mentioned diagnostic difficulty. The immunocytochemical reactivity pattern was evaluated by two independent investigators. The final diagnosis corresponded to PM (n = 20), metastatic adenocarcinoma (n = 83), and mesotheliosis (n = 46) in these cases.

RESULTS

Calretinin had 99% specificity and 98% sensitivity for indicating a mesothelial phenotype, while BerEp4 distinguished the adenocarcinoma cases with 98% specificity and 99% sensitivity. EMA displayed 96% specificity and 99% sensitivity in malignant cases, while Desmin without EMA present showed 99% specificity and 96% sensitivity for indicating benign mesothelial proliferation.

CONCLUSIONS

Interpretation of the four immunoreactions is improved when performed as dual stains. The dual staining is a useful tool in the initial handling of atypical effusions and guides the subsequent choice of antibody panels for more detailed subclassification of malignant effusions.

Immunocytochemistry of effusions: Processing and commonly used immunomarkers

Definitive cytopathological interpretation of some of the effusion fluids may not be possible based on cytomorphological evaluation alone. As discussed in other reviews, this is due to various reasons specifically applicable to effusion fluids including remarkably wide morphologic spectrum of reactive mesothelial cells overlapping with some well to moderately differentiated metastatic carcinoma. The challenge is subject to various factors including level of interpreter training or experience, institutional demographics (such as type of prevalent diseases, predominant sex and age group), technical advances in ancillary support, and expertise in cytopreparatory processing. In such cases immunohistochemistry performed on cell-block sections is simple objective adjunct with or without other ancillary techniques. Ongoing increase in number of immunomarkers along with rabbit monoclonal antibodies with relatively higher affinity is further refining this field. SCIP (subtractive coordinate immunoreactivity pattern) approach, discussed as separate dedicated review article, facilitates refined interpretation of immunoreactivity pattern in coordinate manner on various serial sections of cell-blocks. However, many variables such as delay after specimen collection, specimen processing related factors including fixation and storage; ambient conditions under which paraffin blocks are archived (for retrospective testing); antigen retrieval method; duration of antigen retrieval step; antibody clone and dilution; and antibody application time are common with application of immunohistochemistry in other areas. This review is dedicated to highlight technical aspects including processing of effusion specimens for optimum immunocytochemical evaluation along with commonly used immunomarkers in effusion cytopathology. This review focuses on the technical and general information about various immunomarkers.

Thoracic mesenchymal malignant tumors and programed cell death ligand-1 status: Clinicopathologic and prognostic analysis of eight pulmonary sarcomatoid carcinomas and eight malignant mesotheliomas

BACKGROUND

The current study aimed to evaluate the significance of clinicopathological factors, particularly the immunohistochemistry of programed cell death ligand-1 (PD-L1), in eight cases each of pulmonary sarcomatoid carcinoma (PSC) and malignant pleural mesothelioma (MPM) at our hospital.

METHODS

From January 2004 to December 2020, a total of 16 consecutive patients (eight with PSC and eight with MPM diagnosed via surgical resection or biopsy) were included in this study. After retrospectively reviewing the patient characteristics, the associations between PD-L1 status and age, sex, stage, histological type, and prognosis were investigated.

RESULTS

PD-L1-positive staining was observed in four (50%) PSC cases and one (12.5%) MPM case. Among the four PD-L1-positive PSC cases, two showed high PD-L1 expression in the vimentin-positive sarcomatoid compartment. Moreover, among those with PSC, two survived for about 10 years, whereas the others died within 5 years. No clear correlation was found between PD-L1 expression and prognosis. Among the patients with MPM, four survived for more than 2 years, with the longest being 9 years. Among MPM cases who received nivolumab, one patient with positive PD-L1 staining in the sarcomatoid survived, whereas the other with negative PD-L1 staining did not.

CONCLUSION

The present study showed that sarcomatoid carcinoma had a higher PD-L1 expression compared to non-small-cell lung cancer and that both PSC and MPM tended to exhibit PD-L1 positivity in the sarcomatoid compartment. Moreover, while immune checkpoint inhibitors may somewhat prolong the prognosis of both tumors, further studies with a larger cohort are necessary to confirm our results.

Antibody-Drug Conjugates in Thoracic Malignancies: Clinical Trials Reveal Both Promise and Challenges

Thoracic malignancies are the main cause of cancer-related deaths worldwide. The need to develop new therapies is therefore urgent. The recognition of new potential therapeutic targets in thoracic malignancies has prompted the development of a number of antibody-drug conjugates. This new class of potent anticancer agents is supposed to more specifically and directly target the tumor while limiting toxicity for healthy tissues by delivering a toxic payload to tumor cells that are recognized by the presence of specific cell surface antigens. Progress in the development of antibody-drug conjugates over the last decade has been significant, with several promising advances. Unfortunately, many failures have also been encountered, often because of unexpectedly severe toxicities that contradicted the assumed mechanism of action, and major challenges remain. Various techniques to reduce the toxicities associated with antibody-drug conjugates are being studied, and the panorama of antibody-drug conjugates in clinical stages continues to increase and evolve. Current efforts in the conjugation and linker chemistries could result in the successful construction of clinically effective compounds. The future clinical development of antibody-drug conjugates could benefit from the identification of such payloads that can provide more safe and effective derivatives. Highly potent compounds with reasonable aqueous solubility, non-immunogenic profile, and stability in storage and the bloodstream should be important aspects of research into cytotoxic payloads.

Aberrant Cytokeratin 20 Reactivity in Epithelioid Malignant Mesothelioma: A Case Report

Malignant mesothelioma is an uncommon neoplasm that should be distinguished from the more common pulmonary adenocarcinomas and other metastatic lesions. Although diagnosis is based on morphologic features, immunohistochemical stains such as Calretinin, WT-1, CK-5/6, D2-40, Ber-Ep4, and MOC-31 are routinely used. Other organ-specific immunohistochemical markers are used when metastases from unknown primary lesion is suspected clinically. Here, we report a case of pleural epithelioid malignant mesothelioma expressing CK20. A 68-year-old male presented to the Emergency Department with nonproductive cough and progressive shortness of breath. Chest x-ray showed a large left-sided pleural effusion. Metastasis from a gastrointestinal primary was clinically suspected. Cytopathologic examination of the pleural fluid demonstrated atypical cells singly and in clusters with round nuclei, prominent nucleoli, and dense cytoplasm. The cell block demonstrated single and clusters of atypical cells positive for calretinin, D2-40, WT-1, CK-5/6, and CK7. Ber-EP4, MOC-31, TTF-1, Napsin-A, and CDX-2 were negative. CK20 was diffusely positive. A diagnosis of atypical mesothelial proliferation with aberrant CK20 expression was made. A subsequent pleural biopsy demonstrated sheets of highly atypical cells that were diffusely and strongly positive for the mesothelial markers and CK20. Multiple studies have shown malignant mesotheliomas to lack CK20 reactivity. To our knowledge, this is the first case report of a diffuse and strong CK20-positive mesothelioma. Such aberrant expressions should be kept in mind when cases are histologically atypical or lack reactivity for multiple mesothelial markers, especially when a gastrointestinal primary malignancy is suspected.

Differential Diagnosis of Epithelioid Malignant Mesothelioma With Lung and Breast Pleural Metastasis: A Systematic Review Compared With a Standardized Panel of Antibodies-A New Proposal That May Influence Pathologic Practice

CONTEXT.—

Pleural mesothelioma is a rare cancer with an often-challenging diagnosis because of its potential to be a great mimicker of many other tumors. Among them, primary lung and breast cancers are the 2 main causes of pleural metastasis. The development and application of targeted therapeutic agents have made it even more important to achieve an accurate diagnosis. In this setting, international guidelines have recommended the use of 2 positive and 2 negative immunohistochemical biomarkers.

OBJECTIVES.—

To define the most highly specific and sensitive minimum set of antibodies for routine practice to use for the separation of epithelioid malignant mesothelioma from lung and breast metastasis and to determine the most relevant expression cutoff.

DESIGN.—

To provide information at different levels of expression of 16 mesothelial and epithelial biomarkers, we performed a systematic review of articles published between 1979 and 2017, and we compared those data to results from the Mesothelioma Telepathology Network (MESOPATH) of the standardized panel used in routine practice database since 1998.

RESULTS.—

Our results indicate that the following panel of markers-calretinin (poly)/thyroid transcription factor 1 (TTF-1; clone 8G7G3/1) and calretinin (poly)/estrogen receptor-α (ER-α; clone EP1)-should be recommended; ultimately, based on the MESOPATH database, we highlight their relevance which are the most sensitive and specific panel useful to the differential diagnosis at 10% cutoff.

CONCLUSIONS.—

Highlighted by their relevance in the large cohort reported, we recommend 2 useful panels to the differential diagnosis at 10% cutoff.

Lack of expression of ALK and CD30 in breast carcinoma by immunohistochemistry irrespective of tumor characteristics

CD30 is a member of the tumor necrosis factor family of cell surface receptors normally expressed in lymphocytes, as well as some lymphomas, but has been described in other malignancies. Anaplastic lymphoma kinase (ALK) is a tyrosine kinase receptor that belongs to the insulin receptor superfamily, and is normally expressed in neural cells, but has been detected in several malignancies. There is conflicting data in the literature that describes the expression of these receptors in breast cancer, and the aim of this study is to test the expression of CD30 and ALK in a cohort of Middle Eastern patients with breast carcinoma.Cases of invasive breast cancer from the archives of AUBMC were reviewed over a period of 9 years, and the blocks that were used for immunohistochemical staining for ER, PR, Her-2/neu were selected. Immunohistochemical staining for CD30 (JCM182) and ALK (5A4 and D5F3) was performed.Two hundred eighty-four cases were identified (2 cases were male), with a mean age of 55 ± 12. CD30 and ALK expression was not seen in any of the cases.Our cohort showed complete negativity to both CD30 and ALK, adding to the conflicting data available in the literature, and more studies are needed to reliably identify a trend of expression of CD30 and ALK in breast carcinoma, especially in the Middle East.

A phase 2, open-label study of brentuximab vedotin in patients with CD30-expressing solid tumors

Purpose Brentuximab vedotin (BV) is an anti-CD30 antibody-drug conjugate used in the treatment of several types of lymphomas. Expression of the target antigen has also been reported on a variety of malignant tumors of nonlymphoid origin. This phase 2, open-label study evaluated the safety and antitumor activity of BV in patients with CD30-expressing nonlymphomatous malignancies. Methods Patients were dosed with 1.8 or 2.4 mg/kg BV once every three weeks. Antitumor activity was assessed at Cycles 2, 4, and every 4 cycles thereafter. Patients with stable disease or better were eligible to continue treatment until disease progression, unacceptable toxicity, or study closure. Results Of the 2693 patients screened, 3.8% had solid tumors with CD30 expression and 63 eligible patients with solid tumors enrolled in this study. The most common CD30 positive solid tumors were testicular cancer and mesothelioma. Both subtypes had more than one patient with an objective response. The median duration of BV exposure was 6.1 weeks. The disease control rate, defined as achieving stable disease or better at any point during the study, was 55%. The objective response rate was 11%, with a median duration of response of 2.92 months. The most common adverse events reported were fatigue (57%), nausea (33%), and decreased appetite (32%). Conclusion The safety profile of BV in patients with solid tumors was similar to the known safety profile of BV. In solid tumors, BV had modest activity as a single agent, which was similar to other second-line treatments already available to patients.

Use of the Total Cancer Care System to Enrich Screening for CD30-Positive Solid Tumors for Patient Enrollment Into a Brentuximab Vedotin Clinical Trial: A Pilot Study to Evaluate Feasibility

Background

One approach to identify patients who meet specific eligibility criteria for target-based clinical trials is to use patient and tumor registries to prescreen patient populations.

Objective

Here we demonstrate that the Total Cancer Care (TCC) Protocol, an ongoing, observational study, may provide a solution for rapidly identifying patients with CD30-positive tumors eligible for CD30-targeted therapies such as brentuximab vedotin.

Methods

The TCC patient gene expression profiling database was retrospectively screened for CD30 gene expression determined using HuRSTA-2a520709 Affymetrix arrays (GPL15048). Banked tumor tissue samples were used to determine CD30 protein expression by semiquantitative immunohistochemistry. Statistical comparisons of Z- and H-scores were performed using R statistical software (The R Foundation), and the predictive value, accuracy, sensitivity, and specificity of CD30 gene expression versus protein expression was estimated.

Results

As of March 2015, 120,887 patients have consented to the institutional review board–approved TCC Protocol. A total of 39,157 fresh frozen tumor specimens have been collected, from which over 14,000 samples have gene expression data available. CD30 RNA was expressed in a number of solid tumors; the highest median CD30 RNA expression was observed in primary tumors from lymph node, soft tissue (many sarcomas), lung, skin, and esophagus (median Z-scores 1.011, 0.399, 0.202, 0.152, and 1.011, respectively). High level CD30 gene expression significantly enriches for CD30-positive protein expression in breast, lung, skin, and ovarian cancer; accuracy ranged from 72% to 79%, sensitivity from 75% to 100%, specificity from 70% to 76%, positive predictive value from 20% to 40%, and negative predictive value from 95% to 100%.

Conclusions

The TCC gene expression profiling database guided tissue selection that enriched for CD30 protein expression in a number of solid tumor types. Such an approach may improve screening efficiency for enrolling patients into biomarker-based clinical trials.

Potential application and prevalence of the CD30 (Ki-1) antigen among solid tumors: A focus review of the literature

BACKGROUND

CD30 (Ki-1) is a cell membrane protein derived from the tumor necrosis factor (TNF) receptor family. The CD30 antigen has been associated primarily with Hodgkin lymphoma (HL) and systemic anaplastic large cell lymphoma (sALCL). Brentuximab vedotin (BV) is an antibody-drug conjugate targeting the CD30 antigen. FDA approval for BV includes relapsed and refractory HL and sALCL. The CD30 antigen also has been identified in many solid tumors, predominantly of germ cell origins and early clinical data is promising.

OBJECTIVE

Perform a focus literature review evaluating the prevalence of the CD30 antigen among nonlymphomatous tumors with a potential correlate for CD30 targeted therapy.

ELIGIBILITY CRITERIA

Inclusion criteria: all retrospective reviews and case reports citing CD30 positivity or negativity in non-lymphomatous malignancies in which data were presented based on location.

EXCLUSION CRITERIA

studies with hematopoetic malignancies, cutaneous malignancies, non-human populations, and non-english publications.

INCLUDED STUDIES

A total of 119 articles met these criteria and are summarized in this manuscript.

CONCLUSION

The CD30 antigen has shown variable prevalence among non-hematopoetic tumors, most notably among germ cell tumors and mesothelioma. With additional, preclinical and properly powered clinical studies, CD30 targeted therapy such as that of BV, alone or in combination with other agents may prove to be a strong candidate in the treatment of various CD30⁺ malignancies.

Brentuximab vedotin for treatment of non-Hodgkin lymphomas: A systematic review

BACKGROUND

Brentuximab vedotin (BV) is an antibody-drug conjucate (ADC) comprising a CD30-directed antibody, conjugated to the microtubule-disrupting agent MMAE via a protease cleavable linker. BV is FDA approved for use in relapsed classical Hodgkin lymphoma (HL) and relapsed systemic anaplastic large cell lymphoma (sALCL). There are multiple publications for its utility in other malignancies such as diffuse large B-cell lymphoma (DLBCL), mycosis fungoides (MF), Sézary syndrome (SS), T-cell lymphomas (TCL), primary mediastinal lymphoma (PMBL), and post-transplant lymphoproliferative disorders (PTLD). We believe that BV could potentially provide a strong additional treatment option for patients suffering from NHL.

OBJECTIVE

Perform a systematic review on the use of BV in non-Hodgkin lymphoma (NHL) and other CD30⁺ malignancies in humans.

DATA SOURCES

We searched various databases including PubMed (1946-2015), EMBASE (1947-2015), and Cochrane Central Register of Controlled Trials (1898-2015).

ELIGIBILITY CRITERIA

Inclusion criteria specified all studies and case reports of NHLs in which BV therapy was administered.

INCLUDED STUDIES

A total of 28 articles met these criteria and are summarized in this manuscript.

CONCLUSION

Our findings indicate that BV induces a variety of responses, largely positive in nature and variable between NHL subtypes. With additional, properly powered prospective studies, BV may prove to be a strong candidate in the treatment of various CD30⁺ malignancies.

CD30 as a therapeutic target for lymphoma

Hodgkin's lymphoma (HL) and ALK(+) anaplastic large-cell lymphoma (ALCL) have become highly curable due to the success of modern regimens of chemotherapy and radiotherapy. However, up to one-third of the patients experience relapse or do not respond to first-line therapy, and half of them relapse again after secondary therapy with limited options for further treatment. In the last 15 years, monoclonal antibodies (mAbs) directed to surface receptors became a new and valuable therapeutic option in many hematologic malignancies. Due to its restricted expression on normal activated lymphocytes and its high expression on malignant cells, CD30 represents an attractive target molecule for HL and ALCL therapy. However, unconjugated CD30 mAbs have demonstrated a lack of objective clinical responses in patients with recurrent HL. CD30 exhibits complex signaling pathways, and binding of its natural ligand or anti-CD30 mAbs can induce apoptosis but may also promote proliferation and activation depending on the cellular context. Moreover, CD30 rapidly internalizes after crosslinking, which counteracts efficient recruitment of immunologic effectors but also provides the opportunity to transfer cytotoxic payloads coupled to CD30-specific mAbs into the tumor cells. Several tumor targeting approaches have been studied, including radio-immunoconjugates, immunotoxins, immunoRNases, immunokinases, and antibody drug conjugates (ADCs). In 2011, the ADC brentuximab-vedotin, consisting of the CD30-specific chimeric mAb cAC10 and the potent tubulin toxin monomethyl auristatin E, gained regulatory approval as a well tolerated and highly active drug in patients with refractory and relapsed HL and ALCL. SGN-35 is on the way to being incorporated in the standard management of CD30(+) lymphoma with significant therapeutic impact. This review gives a critical overview about anti-CD30 therapies with unconjugated, engineered, and conjugated mAbs and the therapeutic challenges of treatment of CD30(+) lymphoma.

CD30 is a potential therapeutic target in malignant mesothelioma

CD30 is a cytokine receptor belonging to the TNF superfamily (TNFRSF8) that acts as a regulator of apoptosis. The presence of CD30 antigen is important in the diagnosis of Hodgkin disease and anaplastic large cell lymphoma. There have been sporadic reports of CD30 expression in nonlymphoid tumors, including malignant mesothelioma. Given the remarkable success of brentuximab vedotin, an antibody-drug conjugate directed against CD30 antigen, in lymphoid malignancies, we undertook a study to examine the incidence of CD30 in mesothelioma and to investigate the ability to target CD30 antigen in mesothelioma. Mesothelioma tumor specimens (N = 83) were examined for CD30 expression by IHC. Positive CD30 expression was noted in 13 mesothelioma specimens, primarily those of epithelial histology. There was no significant correlation of CD30 positivity with tumor grade, stage, or survival. Examination of four mesothelioma cell lines (H28, H2052, H2452, and 211H) for CD30 expression by both FACS analysis and confocal microscopy showed that CD30 antigen localized to the cell membrane. Brentuximab vedotin treatment of cultured mesothelioma cells produced a dose-dependent decrease in cell growth and viability at clinically relevant concentrations. Our studies validate the presence of CD30 antigen in a subgroup of epithelial-type mesothelioma tumors and indicate that selected mesothelioma patients may derive benefit from brentuximab vedotin treatment.

Claudin-4 as a marker for distinguishing malignant mesothelioma from lung carcinoma and serous adenocarcinoma

We compared claudin-4 with Ber-EP4 and carcinoembryonic antigen as markers to distinguish mesothelioma from lung adenocarcinoma, poorly differentiated lung squamous cell carcinoma, and serous adenocarcinoma of the uterus or ovary. All mesothelioma specimens were negative for claudin-4, but 3 of 18 specimens were focally positive for Ber-EP4. In contrast, lung adenocarcinoma including poorly differentiated adenocarcinoma was highly positive for claudin-4, but expression of Ber-EP4 and carcinoembryonic antigen varied widely. Claudin-4 in poorly differentiated squamous cell carcinoma had a lower positive expression rate than in adenocarcinoma. Granular claudin-4 immunoreactivity was conspicuous in poorly differentiated squamous cell carcinoma; this immunoreactive pattern was also observed in mesothelioma. Claudin-4 was thus considered very useful marker for distinguishing mesothelioma and adenocarcinoma, even if histological specimens are small, as in biopsies that contain limited numbers of tumor cells. However, it should be mentioned that claudin-4 has a limit in discrimination between squamous cell carcinoma from mesothelioma.

Application of immunohistochemistry in the diagnosis of epithelioid mesothelioma: a review and update

A large number of immunohistochemical markers that can assist in the differential diagnosis of epithelioid mesotheliomas are currently available. Because these markers are expressed differently in the various types of carcinomas that can metastasize to the serosal membranes and can potentially be confused with epithelioid mesothelioma, their selection for inclusion in a diagnostic panel largely depends on the differential diagnosis, as well as on which ones work the best in a given laboratory. Traditionally, the panels used in the differential diagnosis of epithelioid mesothelioma have consisted of a combination of positive mesothelioma markers and broad-spectrum carcinoma markers. At present, a wide variety of organ-associated carcinoma markers such as thyroid transcription factor-1 and napsin A for the lung, PAX 8 and PAX 2 for the kidney, and Müllerian-derived tumors; gross cystic disease fluid protein-15 and mammaglobin for the breast; and CDX2 for intestinal differentiation are available, which can assist in establishing the site of origin of an adenocarcinoma when included in a diagnostic panel. This article provides updated information on the composition of the panels of markers recommended in the various differential diagnoses.

Podoplanin is a useful marker for identifying mesothelioma in malignant effusions

The diagnosis of malignant mesothelioma in serosal effusions continues to be a major challenge because some of its cytomorphological features closely resemble adenocarcinomas. Immunohistochemistry is a valuable tool in the differentiation of epithelioid mesothelioma from metastatic adenocarcinomas. However, no single antibody has demonstrated absolute sensitivity or specificity. In this study, we evaluated the value of immunostaining pattern for podoplanin to differentiate mesothelioma from adenocarcinomas of various origins.Cell blocks from previously collected paraffin-embedded cell blocks of 86 effusions (18 mesothelioma, 35 reactive mesothelium, 9 breast adenocarcinoma, 14 ovarian adenocarcinoma, and 10 lung adenocarcinoma) were retrieved from the file of the Department of Pathology at University of Michigan and Lund University in Sweden and were used for the study. Slides prepared from the cell blocks were stained for podoplanin. The percentage of immunostained cells was recorded as follows: 1+ (5-25%), 2+ (26-50%), and 3+ (>50%). A stain result involving <5% of cells was considered negative. The intensity of positive results was evaluated as strong, moderate, or weak.Podoplanin is expressed in 94% of malignant mesothelioma cases (17/18), 97% (30/31) of cases of reactive mesothelial, 0% of lung adenocarcinoma cases (0/9), 0% of breast adenocarcinoma (0/9), and 7% of ovarian adenocarcinoma (1/14). All positive cases of malignant mesothelioma and reactive mesothelium showed strong membranous reactivity to podoplanin. The one positive case of ovarian adenocarcinoma showed a weak membranous podoplanin immunostaining.On the basis of our results and published data, we believe that membranous podoplanin immunoreactivity, in conjunction with calretinin, would be more specific than CK5/6 and WT-1 in differentiating epithelioid malignant mesothelioma from adenocarcinoma of the lung, breast, and ovary.

Heparanase expression: a potential ancillary diagnostic tool for distinguishing between malignant cells and reactive mesothelium in body cavity effusions

OBJECTIVE

Heparanase, an endoglycosidase that cleaves heparan sulphate, is frequently expressed in carcinomas and was suggested to play a role in cell invasion and metastasis. We investigated whether heparanase expression may serve as a reliable marker to discriminate benign mesothelial cells from malignant cells shed into body cavities.

METHODS AND RESULTS

Cytological smears of effusions from 51 hospitalized patients were immunostained for heparanase. Strong immunoreactivity was noted in 35 of 40 (88%) carcinoma samples and in all three malignant mesothelioma cases. Only rare (<3%) reactive mesothelial cells were noted showing a faint negligible staining. Specificity was 100%, sensitivity 88%, and positive and negative predictive values were 100% and 89% respectively.

CONCLUSIONS

Our results suggest that heparanase may be of value as a complementary component in a diagnostic panel of markers, contributing to its reliability and accuracy.

Immunohistochemical marker panels for distinguishing between epithelioid mesothelioma and lung adenocarcinoma

The distinction between epithelioid mesothelioma and lung adenocarcinoma remains an important diagnostic challenge for surgical pathologists. The aim of the present study was to select a limited and appropriate panel of antibodies that can differentiate between epithelioid mesothelioma and lung adenocarcinoma. Specimens of 90 epithelioid mesotheliomas and 51 lung adenocarcinomas obtained from Japanese cases were examined using calretinin, WT1, AE1/AE3, CAM5.2, cytokeratin (CK) 5/6, vimentin, epithelial membrane antigen (EMA), thrombomodulin, CEA, CA19-9, and CA125. Ninety-six percent of epithelioid mesotheliomas were positive for calretinin; 99% for WT1; 100% for AE1/AE; 97% for CAM5.2; 70% for CK 5/6; 91% for vimentin; 96% for EMA; 71% for thrombomodulin; 77% for mesothelin; 7% for CEA; 17% for CA19-9; and 85% for CA125. In contrast, 33% of lung adenocarcinomas were positive for calretinin; 16% for WT1; 100% for AE1/AE3, CAM5.2, and EMA; 41% for CK 5/6; 47% for vimentin; 20% for thrombomodulin; 69% for mesothelin; 98% for CEA; 73% for CA19-9; and 80% for CA125. For distinguishing between epithelioid mesothelioma and lung adenocarcinoma, the combination of CEA, calretinin and each WT1 or thrombomodulin was suggested to be the best panel of immunohistochemical markers.

What are the current best immunohistochemical markers for the diagnosis of epithelioid mesothelioma? A review and update

Numerous immunohistochemical markers that can assist in the diagnosis of epithelioid mesotheliomas, some of which have only recently been recognized, are currently available. Because the various types of carcinomas express these markers differently, their selection for inclusion in a diagnostic panel can vary according to the differential diagnosis. This article provides a critical review of all of the information that is presently available on those markers that are believed to have the greatest potential for assisting in distinguishing between epithelioid mesotheliomas and those carcinomas with which they are most likely to be confused. Information is also provided regarding the panels of immunohistochemical markers that are, at present, recommended in these differential diagnoses.

Applications and limitations of immunohistochemistry in the diagnosis of malignant mesothelioma

Malignant mesothelioma is an uncommon malignant epithelial neoplasm originating from the serosal surface of body cavities. Because serosal surfaces are a common site of metastatic spread for a variety of malignant neoplasms originating from internal organs, separating malignant mesothelioma from metastatic tumors is of clinical importance. The diagnosis of malignant mesothelioma is complex and usually requires a multimodal approach that includes careful clinical history and physical examination, imaging studies, and tissue sampling for multimodal evaluation including routine histology, histochemistry, electron microscopy, and immunohistochemical tests. Of these, immunohistochemistry has emerged as the most valuable and readily available modality for the routine evaluation of these tumors. Unfortunately, no specific antibodies have yet been developed that can be accepted as exclusive for these tumors. The immunohistochemical diagnosis of malignant mesothelioma therefore depends on the use of a panel of stains that includes markers that are commonly expected to react with these tumors ("positive" markers) and markers that are not commonly expected to react with these tumors ("negative" markers). Additionally, the selection and utility of these various markers can vary considerably based on a constellation of circumstances, including patient sex, histologic appearance of the tumor (ie, epithelioid vs. sarcomatoid, etc), and various other clinical circumstances. Herein, we will review the currently available immunohistochemical markers used for the diagnosis of malignant mesothelioma and offer suggestions for the use of appropriate panels of stains based on specific morphologic types and clinical circumstances.

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.

h-Caldesmon, a Useful Positive Marker in the Diagnosis of Pleural Malignant Mesothelioma, Epithelioid Type

Although a large number of immunohistochemical markers that can facilitate the differential diagnosis between epithelioid pleural mesothelioma and lung adenocarcinoma involving the pleura have proven to be valuable, no single antibody has demonstrated absolute sensitivity and/or specificity in making this distinction. Using immunohistochemical analysis with h-caldesmon, a specific marker for smooth muscle tumors, we examined 70 cases of epithelial mesotheliomas and 70 cases of lung adenocarcinomas. In addition, immunohistochemistry for muscle markers, such as desmin, alpha-smooth-muscle actin, muscle-specific actin, myoglobin, myogenin, myosin, and MyoD-1, was performed on all mesothelioma cases. Reactivity for h-caldesmon was obtained in 68 (97%) of the 70 epithelial mesotheliomas, but in none of the adenocarcinoma cases. All mesothelioma cases were found to be negative for the other muscle markers examined. We conclude that h-caldesmon is a highly sensitive and specific marker and suggest its inclusion in the immunohistochemical panel for the differential diagnosis of epithelioid mesothelioma versus lung adenocarcinoma.

Mesothelioma with rhabdoid features: an ultrastructural and immunohistochemical study of 10 cases

Mesotheliomas with rhabdoid morphology are rare and only two individual case reports have been documented in the literature. This author reports a series of 10 cases of mesotheliomas with rhabdoid features, nine of which originated in the pleura and one in the peritoneum. Eight of the patients were men and two were women. Six patients had a history of asbestos exposure. Histologically, seven of the mesotheliomas were epithelioid, two sarcomatoid, and one biphasic. The proportion of the rhabdoid cells seen in these cases constituted 15-75% of the individual tumors. Cytoplasmic staining in the rhabdoid cells was seen for pan-keratin and vimentin in all 10 cases, for keratin 7 in eight of eight, for calretinin in nine of 10, and for keratin 5/6 in seven of nine. Nuclear positivity for WT1 was observed in the rhabdoid cells of four of seven cases and membranous reactivity for mesothelin in four of six, and for podoplanin in two of six. Only one case showed desmin positivity in sparse cells in the nonrhabdoid component of the tumor. All of the cases were negative for CEA, MOC-31, TAG-72, CD15, CD34, bcl2, muscle-specific actin, and TTF-1. Ultrastructural studies revealed paranuclear collections of intermediate filaments, but no evidence of rhabdomyoblastic differentiation was seen. The mean survival of five of the six patients for whom this information was available was 3.8 months. The remaining patient had a survival time of 1 year. It is important for pathologists to be aware that mesotheliomas can present rhabdoid features, not only because they can be confused with other malignancies that can exhibit a similar morphology, but also because of their apparently unusually aggressive behavior. The value of immunohistochemistry and electron microscopy in the differential diagnosis of these tumors is discussed.

Sensitivity and specificity of immunohistochemical markers used in the diagnosis of epithelioid mesothelioma: a detailed systematic analysis using published data

AIMS

Immunohistochemistry is frequently employed to aid the distinction between mesothelioma and pulmonary adenocarcinoma metastatic to the pleura, but there is uncertainty as to which antibodies are most useful. We analysed published data in order to establish sensitivity and specificity of antibodies used to distinguish between these tumours with a view to defining the most appropriate immunohistochemical panel to use when faced with this diagnostic problem.

METHODS AND RESULTS

A systematic analysis of the results of 88 published papers comparing immunohistochemical staining of a panel of antibodies in mesothelioma with epithelioid areas, and pulmonary adenocarcinoma metastatic to the pleura. Results for a total of 15 antibodies were analysed and expressed in terms of sensitivity and specificity. The most sensitive antibodies for identifying pulmonary adenocarcinoma were MOC-31 and BG8 (both 93%), whilst the most specific were monoclonal CEA (97%) and TTF-1 (100%). The most sensitive antibodies to identify epithelioid mesothelioma were CK5/6 (83%) and HBME-1 (85%). The most specific antibodies were CK5/6 (85%) and WT1 (96%).

CONCLUSIONS

No single antibody is able to differentiate reliably between these two tumours. The use of a small panel of antibodies with a high combined sensitivity and specificity is recommended.

Ber-H2 (CD30) immunohistochemical staining of human fetal tissues

OBJECTIVE: CD30 antigen has long been considered to be restricted to the tumour cells of Hodgkin's disease and of anaplastic large cell lymphoma as well as to T and B activated lymphocytes. It is now apparent that the range of normal and neoplastic cells, which may express CD30 antigen, is much wider than was at first thought. In order to gain insight into the physiological function of CD30 antigen, we studied the distribution of its expression in the tissues of fetuses from week 8^th to week 16^th.

MATERIALS AND METHODS: We investigated the immunohistochemical expression of CD30 antigen in paraffin-embedded tissue samples representing all systems from 30 fetuses after therapeutic abortion at 8^th to 10^th and 12^th to 16^th week of gestation, respectively, using the monoclonal antibody Ber-H2.

RESULTS: Our results demonstrated that CD30 is expressed early in human fetal development (8^th to 10^th week of gestation) in several fetal tissues derived from all three germ layers (gastrointestinal tract, special glands of the postpharyngeal foregut, urinary, musculoskeletal, reproductive, nervous, endocrine systems), with the exception of the skin and hematolymphoid system (thymus), in which the antigen is expressed later on (10^th week onwards). Expression of CD30 was restricted to the hematolymphoid system in the 12-16 weeks of gestation. No expression of the marker was observed in the respiratory and cardiovascular systems during the entire period examined.

CONCLUSIONS: CD30 antigen is of importance in cell development, and proliferation. It is also pathway-related to terminal differentiation in many fetal tissues and organs.

Lymphohistiocytoid mesothelioma: a clinical, immunohistochemical and ultrastructural study of four cases and literature review

Lymphohistiocytoid mesothelioma (LHM) is a term proposed to designate a variant of mesothelioma that assumes a histiocytoid morphology and contains intense lymphocytic infiltrates. Reports on this variant are few, and its clinicopathologic and ultrastructural characteristics are still to be defined. The authors have studied 4 such cases that were identified among 120 mesotheliomas in the electron microscopy (EM) files of a single institution between 1982 and 2002. Histologically, all 4 lesions were composed of diffuse proliferations of cells with a histiocytoid appearance, admixed with an intense lymphocytic infiltrate. All 4 were associated with an unequivocal sarcomatoid component. Immunohistochemical (IHC) studies showed that the majority of histiocytoid cells were positive for CD68 and vimentin in all 4 cases, suggesting fibrohistiocytic differentiation. Immunoreactivity for calretinin and AE1:AE3 was only very focally identified in 3 of 4 cases. All cases were negative for CEA (M), Leu-M1, and B72.3. The lymphocytic component in all 4 cases was almost entirely composed of CD3- and CD8-positive, small, mature T cells, with only a minor component of CD20-positive cells and occasional eosinophils. Although all cases contained numerous CD68 positive atypical cells, co-expression of CD68 and either calretinin or keratin by individual cells was difficult to demonstrate by immunohistochemistry. Ultrastructurally, 3 of the 4 cases demonstrated very focal mesothelial differentiation as evidenced by long and slender surface microvilli, including the case with negative immunoreactivity for calretinin and cytokeratin. Review of the literature yielded 6 additional LHM cases. Analysis of all 10 cases showed a male predominance (8:2) with a mean age of 58 years (31-73 years). All 10 cases involved the pleura. Three of 10 patients had known asbestos exposure. Six of 10 patients died of disease at 2-20 months after the diagnosis (mean, 6.9 months). The findings suggest that LHM is a distinct morphological variant of sarcomatoid mesothelioma for which mesothelial differentiation is difficult to document. Many of the cells composing these tumors exhibit fibrohistiocytic differentiation. The unusual morphological pattern of LHM makes a combined modality approach, including IHC, EM, and a knowledge of the clinical/radiologic findings, essential in achieving a correct diagnosis.

Human embryonal epithelial cells of the developing small intestinal crypts can express the Hodgkin-cell associated antigen Ki-1 (CD30) in spontaneous abortions during the first trimester of gestation

BACKGROUND

Ki-1 (CD30) antigen expression is not found on peripheral blood cells but its expression can be induced in vitro on T and B lymphocytes by viruses and lectins. Expression of CD30 in normal tissues is very limited, being restricted mainly to a subpopulation of large lymphoid cells; in particular, cells of the recently described anaplastic large cell lymphoma (ALCL), the Reed-Sternberg (RS) cells of Hodgkin's lymphoma and scattered large parafollicular cells in normal lymphoid tissues. More recent reports have described CD30 expression in non-hematopoietic and malignant cells such as cultured human macrophages, human decidual cells, histiocytic neoplastic cells, mesothelioma cells, embryonal carcinoma and seminoma cells.

RESULTS

We investigated the immunohistochemical expression of CD30 antigen in 15 paraffin-embedded tissue samples representing small intestines from fetuses after spontaneous abortion in the 8th, 10th and 12th weeks using the monoclonal antibody Ki-1. Hormones had been administered to all our pregnant women to support gestation. In addition, a panel of monoclonal antibodies was used to identify leukocytes (CD45/LCA), B-lymphocytes (CD20/L-26) and T-lymphocytes (CD3). Our findings were correlated with those obtained simultaneously from intestinal tissue samples obtained from 15 fetuses after therapeutic or voluntary abortions.

CONCLUSIONS

The results showed that: (1) epithelial cells in the developing intestinal crypts express the CD30 (Ki-1) antigen; (2) CD30 expression in these epithelial cells is higher in cases of hormonal administration than in normal gestation. In the former cases (hormonal support of gestation) a mild mononuclear intraepithelial infiltrate composed of CD3 (T-marker)-positive cells accompanies the CD30-positive cells.

‘Pseudomesotheliomatous’ carcinomas of the pleura: a 10-year analysis of cases from the Environmental Lung Disease Research Group, Cardiff

AIMS

To undertake a clinicopathological study of diffuse serosal neoplasms of epithelial histogenesis which clinically and pathologically mimic malignant pleural mesothelioma.

METHODS AND RESULTS

Over a 10-year (1990-2000) study period 53 carcinomas mimicking diffuse pleural mesothelioma ('pseudomesotheliomatous' carcinoma) were identified. The study group comprised 50 men and three females, age range 33-77 (median 68) years. In 46 (87%) cases there was a history of smoking and in 40 (76%) cases a history of asbestos exposure. Histologically the pleural 'pseudomesotheliomatous' carcinomas could be divided into two broad groups: primary pulmonary carcinomas with florid pleurotropic growth (n = 47), of which 34 (70%) were adenocarcinomas; and diffuse carcinomatous involvement of the pleura by metastatic tumour (n = 6). This latter group comprised two transitional cell carcinomas of bladder, one renal (clear) cell carcinoma, one ductal pancreatic adenocarcinoma, one prostatic adenocarcinoma and one squamous cell carcinoma of parotid gland origin. Follow-up data were available in 35 cases. Regardless of tumour type, survival was poor (median 8 months) and comparable to diffuse pleural mesothelioma.

CONCLUSIONS

Pleural 'pseudomesotheliomatous' carcinomas are uncommon (comprising 6% of referrals), pathologically heterogeneous tumours with poor prognosis. Tissue diagnosis should be obtained in all cases of suspected diffuse pleural neoplasia. By light microscopy and immunophenotype many of the tumours mimicked malignant mesothelioma. In particular, an awareness that all neoplasms exhibiting squamous differentiation may express cytokeratin 5/6 and thrombomodulin is important to prevent misinterpretation. In this respect, calretinin is regarded as the most specific and sensitive mesothelial marker. Misdiagnosis may have medico-legal implications in asbestos-related compensation claims.

The immunohistochemical diagnosis of mesothelioma: a comparative study of epithelioid mesothelioma and lung adenocarcinoma

A large number of immunohistochemical markers that can facilitate the distinction between epithelioid pleural mesotheliomas and pulmonary peripheral adenocarcinomas have recently become available. The aim of this study is to compare the value of these new markers with others that are already commonly used for this purpose and to determine which are, at present, the best for discriminating between these malignancies. Sixty epithelioid mesotheliomas and 50 lung adenocarcinomas were investigated for expression of the following markers: calretinin, cytokeratin 5/6, WT1, thrombomodulin, mesothelin, CD44S, HBME-1, N-cadherin, E-cadherin, MOC-31, thyroid transcription factor-1 (TTF-1), BG-8 (Lewisy), carcinoembryonic antigen (CEA), Ber-EP4, B72.3 (TAG-72), leu-M1 (CD15), CA19-9, epithelial membrane antigen (EMA), and vimentin. All (100%) of the mesotheliomas reacted for calretinin, cytokeratin 5/6, and mesothelin, 93% for WT1, 93% for EMA, 85% for HBME-1, 77% for thrombomodulin; 73% for CD44S, 73% for N-cadherin, 55% for vimentin, 40% for E-cadherin, 18% for Ber-EP4, 8% for MOC-31, 7% for BG-8, and none for CEA, B72.3, leu-M1, TTF-1, or CA19-9. Of the adenocarcinomas, 100% were positive for MOC-31, Ber-EP4, and EMA, 96% for BG-8, 88% for CEA, 88% for E-cadherin, 84% for B72.3, 74% for TTF-1, 72% for leu-M1, 68% for HBME-1, 48% for CD44S, 48% for CA19-9, 38% for mesothelin, 38% for vimentin, 30% for N-cadherin, 14% for thrombomodulin, 8% for calretinin, 2% for cytokeratin 5/6, and none for WT1. After analyzing the results, it is concluded that calretinin, cytokeratin 5/6, and WT1 are the best positive markers for differentiating epithelioid malignant mesothelioma from pulmonary adenocarcinoma. The best discriminators among the antibodies considered to be negative markers for mesothelioma are CEA, MOC-31, Ber-EP4, BG-8, and B72.3. A panel of four markers (two positive and two negative) selected based upon availability and which ones yield good staining results in a given laboratory is recommended. Because of their specificity and sensitivity for mesotheliomas, the best combination appears to be calretinin and cytokeratin 5/6 (or WT1) for the positive markers and CEA and MOC-31 (or B72.3, Ber-EP4, or BG-8) for the negative markers. An extensive and detailed review of the literature is also provided.

A poorly differentiated pulmonary squamous cell carcinoma in a free-ranging Atlantic bottlenose dolphin (Tursiops truncatus)

A free-ranging, adult, female offshore bottlenose dolphin (Tursiops truncatus) was found freshly dead in 1999 on Ocean Park Beach in San Juan, Puerto Rico. The left-lung and right-lung pleura had multiple white, firm-to-hard nodules with coagulative necrosis. Histologically, the neoplasms were characterized by multiple well-circumscribed, nonencapsulated expansile masses consisting mostly of polygonal cells with fewer circumferential flattened basaloid cells that compressed alveoli, bronchioles, and bronchi. Neoplastic cells stained positive for cytokeratin, with sporadic vimentin staining, and were negative for epithelial membrane antigen, thyroid transcription factor-1, calretinin, and human mesothelial cell antigen. A diagnosis of poorly differentiated pulmonary squamous cell carcinoma with lymph node and renal metastases was made on the basis of histomorphology and immunohistochemical staining. This is the first documentation of pulmonary squamous cell carcinoma in a dolphin.

Immunohistochemical diagnosis of epithelioid mesotheliomas: a critical review of old markers, new markers

Numerous new immunohistochemical markers that can be used in the diagnosis of mesothelioma have recently become available. As a result, new panels of antibodies that could be useful for distinguishing between epithelioid mesotheliomas and adenocarcinomas have been proposed. However, great differences of opinion exist regarding the individual value of some of these markers, especially when compared with those whose value has already been established. This article provides a critical review of the currently available information on those markers that could be useful in the diagnosis of epithelioid mesotheliomas or whose utility remains controversial. A practical approach to the diagnosis of these tumors is also provided.

Cytokeratins 20 and 7 as biomarkers: usefulness in discriminating primary from metastatic adenocarcinoma

Metastatic adenocarcinoma from an unknown primary site is a common clinical problem. The use of cytokeratins 20 (CK20) and 7 (CK7) was proposed to identify the primary sites in this situation. In this review, the results of 29 studies were summarised and the difficulties of data comparison described. Most tumours retained the CK20 phenotype during metastasis, but lung, non-mucinous ovarian, and gastric adenocarcinomas showed statistically significant differences in CK20 expression in the reported primary and metastatic cases. Ductal breast carcinomas, lung and non-mucinous ovarian adenocarcinomas showed significant differences in CK7 expression when primary and metastatic tumours were compared. CK20 positivity alone indicates metastatic spread of adenocarcinoma in several organs. CK7 negativity is consistent with metastases of adenocarcinomas in the lungs, ovaries, liver or serous membranes. CK20/7 phenotyping of adenocarcinomas is a useful diagnostic tool if based on algorithmic and probabilistic approaches and a detailed database.

Use of magnetic enrichment for detection of carcinoma cells in fluid specimens

BACKGROUND

Ascites fluid or a pleural effusion are common events in metastatic carcinoma, but they also can be associated with several other medical conditions. The standard for determination of malignancy in these situations is cytologic evaluation of these fluids. Although this method is frequently successful, there are times when it fails, even when the patient has a malignancy, either because of insufficient cells in the fluid or for other reasons. This study addresses this problem taking advantage of the recent advances in technology for detection of rare epithelial cells in liquid specimens.

METHODS

The authors examined fluid specimens from 59 patients to determine the frequency of recovery of epithelial cells compared with that achieved by conventional cytopathology. The Dynal CELLection Epithelial Enrich (Dynal AS, Oslo, Norway) method was used. This method is based on immunomagnetic selection of cells binding to EpCAM antibodies. Carcinoma cells were confirmed by morphology and, when there was sufficient material, by E-cadherin staining.

RESULTS

Grouping the cases by cytologic diagnosis, the authors found malignant cells using the cell enrichment assay in 11 of 12 malignant cases, 2 of 5 atypical cases, and 3 of 42 negative cases. Further investigations were conducted on the five cases that were cytologically negative or atypical but yielded epithelial cells after immunomagnetic enrichment. Four cases ultimately were proven malignant by other methods and one had incomplete follow-up.

CONCLUSIONS

The new methods available for epithelial cell enrichment in liquids may be used successfully on cytologic fluid specimens and may lead to increased sensitivity for detection of malignancy, and consequently more accurate staging.

The value of cytokeratins 20 and 7 in discriminating metastatic adenocarcinomas from pleural mesotheliomas

BACKGROUND

Immunohistochemistry is a useful method in the differential diagnosis between pleural mesotheliomas and metastatic adenocarcinomas to the pleura. Cytokeratin (CK) 5-6 is one of the most specific mesothelioma-associated antibodies. Cytokeratin 20 and CK7 have been used successfully in studies determining primary location of adenocarcinomas from metastases. In the current study, the value of these CKs in differential diagnosis of malignant pleural lesions was examined.

METHODS

Ninety-three autopsy-verified cases (14 mesotheliomas and 79 adenocarcinomas including 42 primary lung tumors and 37 adenocarcinomas metastatic to the pleura) were stained on CK20, CK7, and CK5-6 with commercially available primary antibodies. The staining was conducted in an automated immunohistochemical system. The results were analyzed statistically at different positivity thresholds: 10% and 0%.

RESULTS

None of the mesotheliomas stained positively for CK20 at the 10% positivity level, but 3 cases showed focal positivity in < 10% of the tumor cells. Eighty-six percent (12 of 14) of these tumors were CK7+ and 64% (9 of 14) were CK5-6+. None of the mesotheliomas expressed the CK20+/7- pattern. Lung adenocarcinomas, both primary and metastatic, and breast carcinomas were very similar to mesotheliomas with regard to expression of CK20 and CK7 but differed significantly with regard to expression of CK5-6. Conversely, gastrointestinal adenocarcinomas and pancreaticobiliary tumors expressed CK20 positivity in a high proportion, 86% (13 of 15) and 77% (7 of 9), respectively. The gastrointestinal tumors stained positively for CK7 in only 20% (3 of 15) of cases and differed significantly from the other adenocarcinomas in this aspect. The CK20+/7- pattern was typical for gastrointestinal tumors.

CONCLUSIONS

Adding CK20 and CK7 to the panel of antibodies in the differential diagnosis of pleural mesothelioma versus metastatic adenocarcinomas is useful because diffuse CK20 positivity seems to be an indicator of metastasis. Furthermore, CK7 negativity most often is associated with metastases, and the CK20+/7- pattern, typical of colorectal adenocarcinomas, is absent in pleural mesotheliomas.

The role of desmin and N-cadherin in effusion cytology: a comparative study using established markers of mesothelial and epithelial cells

The objective of the present study was to analyze the role of the mesothelial markers desmin and N-cadherin in the diagnostic panel of serous effusions. A total of 181 pleural and peritoneal effusions consisted of 101 cases cytologically diagnosed as malignant (89 carcinomas, 12 mesotheliomas), 78 benign, and 2 inconclusive specimens. All specimens were immunostained using 11 antibodies, against epithelial membrane antigen, Ber-EP4, carcinoembryonic antigen, E-cadherin, CA 125, N-cadherin, desmin, calretinin, p53, vimentin, and CD45. After evaluation of immunocytochemistry results, 110 specimens were diagnosed as malignant (98 carcinomas, 12 mesotheliomas) and 71 as benign (56 cellular, 15 paucicellular). The presence of desmin was detected in benign mesothelial cells in 47 of 56 (84%) reactive cellular specimens compared with 1 of 12 (8%) malignant mesotheliomas and 2 of 98 (2%) carcinomas. N-cadherin was expressed in 48 of 56 (86%) reactive cases, 12 of 12 (100%) mesotheliomas, and 47 of 98 (48%) carcinomas. In carcinomas, N-cadherin expression was most often seen in ovarian carcinoma but was also found in other carcinomas. Calretinin, an established marker of mesothelial cells, was detected in 52 of 56 (93%) reactive specimens, 11 of 12 (93%) mesotheliomas, and 3 of 98 (3%) carcinomas. Evaluation of staining results led to reclassification of six malignant specimens as benign, whereas 17 cases diagnosed as benign and the two diagnosed as inconclusive were classified as malignant. In conclusion, desmin appears to be a promising marker for the distinction between reactive mesothelium and malignant epithelial cells in terms of both specificity and sensitivity, and its complementary use with calretinin is recommended. Unlike calretinin, it may also prove valuable for the distinction between benign and malignant mesothelial cells. N-cadherin does not have a role in the distinction between mesothelial and epithelial cells. However, it may prove useful in the characterization of carcinomas of unknown origin. As has previously been shown, a significant number of diagnoses that are based on morphologic examination alone are modified after the use of a broad antibody panel.

Ber-EP4 immunoreactivity depends on the germ layer origin and maturity of the squamous epithelium

AIM

To map the expression of Ber-EP4 in well-differentiated squamous epithelia, metaplastic squamous epithelia and dysplastic squamous epithelia of different origins.

METHODS AND RESULTS

Squamous epithelium of different origin was stained using a standard immunohistochemistry method applied to paraffin sections. We found that normal squamous epithelium of the oral cavity, oesophagus, uterine cervix, vagina, anal canal, and branchial cysts are Ber-Ep4-negative, as are the mature squamous metaplasia of bronchial mucosa, urinary bladder mucosa and uterine cervical mucosa. In contrast, immature squamous metaplasia of bronchial mucosa, or uterine cervical mucosa, and squamous dysplasia of oral mucosa of endodermal origin, or uterine cervical mucosa in most cases expressed Ber-EP4.

CONCLUSION

Squamous epithelia of ectodermal origin never express Ber-EP4, whether normal, hyperplastic, dysplastic or neoplastic. In contrast, squamous epithelium of endodermal origin sometimes contains the target glycoproteins of Ber-EP4 when immature, metaplastic, dysplastic or neoplastic. The results indicate that the differences in expression of Ber-EP4 in squamous epithelium depend primarily on germ layer origin, and on the maturity of the epithelium.

Malignant mesothelioma: a comparison of biopsy and postmortem material by light microscopy and immunohistochemistry

AIMS

The diagnosis of malignant mesothelioma in pleural biopsies can be difficult. Survival is short and consequently many of these cases are submitted to necropsy to assist with medicolegal claims. This study compares the histological appearances and immunohistochemical profile of nine biopsy specimens with corresponding postmortem specimens.

METHODS

Archival, formalin fixed, paraffin wax embedded material was obtained from nine biopsy and corresponding postmortem cases of malignant mesothelioma. The specimens were examined by light microscopy and stained with an immunohistochemical panel of 12 commercially available antibodies including CAM5.2, HBME-1, and Ber-EP4, and antibodies to thrombomodulin, calretinin, CD44H, WT-1, carcinoembryonic antigen, Leu-M1, epithelial membrane antigen and p53.

RESULTS

There was greater variation in the range of histological appearances of mesotheliomas in postmortem specimens compared with biopsy specimens. There was also variability in the immunohistochemical staining pattern for certain antibodies including HBME-1, and Ber-EP4 and antibodies to calretinin, CD44H, WT-1, and p53.

CONCLUSIONS

All available information should be taken into account in the histological diagnosis of malignant mesothelioma. Interpretation of the immunohistochemical profile should be regarded with some caution when only postmortem material is available. When reporting a postmortem case of suspected mesothelioma, the pathologist should seek to review all available biopsy material in conjunction with the necropsy.

Immunohistochemical analysis of nuclear versus cytoplasmic staining of WT1 in malignant mesotheliomas and primary pulmonary adenocarcinomas

CONTEXT

Previous studies have indicated certain immunohistochemical markers, including WT1, may be helpful in distinguishing adenocarcinomas from mesotheliomas, but to date there are no reliable, widely accepted, commercially available antibodies positive in mesotheliomas and negative in adenocarcinomas. We compared the nuclear and cytoplasmic staining patterns of WT1 in these 2 malignancies using a commercially available antibody and examined the expression of 2 other previously reported positive markers, calretinin and thrombomodulin.

METHODS

Sixty-seven mesotheliomas and 51 adenocarcinomas, all paraffin embedded, were retrieved from recent case files. The diagnosis of mesothelioma was based on typical clinical and morphologic features, as well as immunohistochemistry; electron microscopy had been performed on 16 cases. The diagnosis of adenocarcinoma was based on typical light microscopic findings and a positive stain for mucin. Commercially available antibodies to WT1, thrombomodulin, and calretinin were applied. Because of the conflict surrounding calretinin, 2 anticalretinin antibodies (from Chemicon Inc and Zymed Laboratories) were utilized.

RESULTS

Fifty of 67 mesotheliomas showed strong nuclear staining with WT1. No adenocarcinomas (0/51) showed nuclear staining. Twenty-three of 67 mesotheliomas were positive for thrombomodulin, and 35 of 67 mesotheliomas were positive for calretinin with the Chemicon antibody. Nine of 15 mesotheliomas were positive for calretinin with the Zymed antibody.

CONCLUSIONS

Thrombomodulin and calretinin did not prove useful in discriminating between mesotheliomas and adenocarcinomas. The degree of positivity with calretinin may be dependent on the specific antibody utilized. Nuclear staining for WT1 is highly specific for mesothelioma and, in the appropriate clinical setting, can be a helpful adjunct in the distinction between adenocarcinomas and mesotheliomas.

Immunohistochemical analysis still has a limited role in the diagnosis of malignant mesothelioma. A study of thirteen antibodies

To identify the most accurate and useful panel to diagnose mesothelioma, we immunostained sections from 112 mesotheliomas, 18 adenocarcinomas, and 11 reactive pleural specimens with 13 antibodies. Positive results for mesotheliomas, adenocarcinomas, and reactive pleura, respectively, were CAM5.2, 111, 18, and 11; vimentin, 30, 3, and 3; HBME-1, 75, 10, and 8; thrombomodulin, 31, 2, and 2; calretinin, 43, 6, and 11; and CD44H, 68, 10, and 4. Positive results for adenocarcinoma markers in mesotheliomas and adenocarcinomas, respectively, were carcinoembryonic antigen, 1 and 15; LeuM1, 7 and 9; and Ber-EP4, 5 and 12. All reactive pleura were negative. Positive results for markers to help distinguish mesothelioma from reactive pleura in mesotheliomas, adenocarcinomas, and reactive pleura, respectively, were epithelial membrane antigen, 76, 17, and 6; p53, 78, 16, and 9; P-170 glycoprotein, 37, 4, and 2; and platelet-derived growth factor receptor beta, 31, 1, and 2. The differential diagnosis of mesothelioma from adenocarcinoma is based on negative markers. Individual mesothelial markers are of low sensitivity and specificity for mesothelioma. However, diagnostic accuracy is improved by the use of antibody panels. To date there are no antibodies that help distinguish mesothelioma from reactive pleura.

Immunohistochemical differential diagnosis of pleural effusions, with emphasis on malignant mesothelioma

The immunohistochemical diagnosis of atypical epithelial proliferations in pleural fluid is a challenging topic in cytopathology and surgical pathology. Mesothelioma may be simulated clinically and radiologically by several other nonneoplastic and neoplastic disorders, mandating that strict histologic, histochemical, immunohistochemical, and ultrastructural guidelines be followed for its diagnosis. Because of its availability to most laboratories, immunohistochemistry has emerged as the most commonly used procedure for the diagnosis of pleural malignancies. This review considers the current status of that investigative modality, with particular attention to lesions that are suspected to be mesothelial.