Diagnostic utility of calretinin immunohistochemistry in cytologic cell block preparations

BAP1 and Claudin-4, But Not MTAP, Reliably Distinguish Borderline and Low-grade Serous Ovarian Tumors From Peritoneal Mesothelioma

Peritoneal mesothelioma (PM) and serous neoplasms can be difficult to differentiate, particularly in small biopsies. BRCA1-associated protein 1 (BAP1) is expressed in benign tissues, but over 50% of PMs demonstrate complete loss of nuclear expression. Claudin-4, a tight junction protein, is expressed in most epithelial tumors but not in mesotheliomas. Methylthioadenosine phosphorylase (MTAP) is frequently co-deleted with cyclin-dependent kinase inhibitor 2a in mesotheliomas. These markers have proven useful in separating mesothelioma from its mimics, particularly when tumors are pleural based. In the peritoneum, BAP1 loss has been rarely reported in high-grade serous carcinomas, but overall, these markers have been minimally evaluated in ovarian serous borderline tumors and low-grade serous carcinomas. Thus, we assessed the utility of BAP1, claudin-4, and MTAP in the differential diagnosis of PM and low-grade serous neoplasms. Eighteen PM (16 epithelioid, 1 biphasic, and 1 sarcomatous), 24 low-grade serous carcinomas, and 25 serous borderline tumors were stained for BAP1, claudin-4, and MTAP. Loss of BAP1 nuclear expression was observed in 12 (67%) PM (11 epithelioid, 1 biphasic) but was retained in all serous tumors. Claudin-4 was positive in all serous tumors and negative in all PM. Complete loss of cytoplasmic MTAP was noted in 3 (17%) PMs and 1 (4%) serous borderline tumor, while all low-grade serous carcinomas showed retained expression. BAP1 loss reliably distinguishes PM from serous tumors, although it lacks sensitivity. Claudin-4 is a reliable marker to exclude PM. MTAP loss may occur in both PM and serous tumors, and thus is not useful in distinguishing these entities.

Immunocytochemistry of effusion fluids: Introduction to SCIP approach

Due to the remarkably wide morphologic spectrum of reactive mesothelial cells, some of the effusion fluids may be difficult to interpret with objective certainty by cytomorphology alone. Cytomorphology of well to moderately differentiated adenocarcinomas (responsible for the bulk of malignant effusions) may overlap with floridly reactive mesothelial cells. Even mesotheliomas including diffuse malignant epithelioid mesothelioma, are usually cytomorphologically bland without unequivocal features of malignancy. The intensity of challenge depends on the interpreter's training or experience level, institutional demographics of patients (such as type of prevalent diseases, predominant sex and age group), technical support, and quality of cytopreparatory processing. In general immunocytochemistry is valuable adjunct to facilitate objective interpretation with or without other ancillary techniques as indicated. An increasing number of immunomarkers is further refining the contribution of immunohistochemistry to this field. However, application of immunohistochemistry to effusion fluids is relatively challenging because of many variables. Multiple factors 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 identical to application of immunohistochemistry in other areas. The significant challenge related to the potential compromization of the immunoreactivity pattern due to exposure to non-formalin fixatives / reagents is also applicable to effusion fluid specimens. The immunoreactivity results would be compared and corelated with cumulative metadata based on the reported studies performed and validated on formalin-fixed paraffin-embedded tissue sections. Deviating from such protocols may lead to suboptimal results, which is not uncommon in clinical practice with potential compromization of patient care and related liability. Because of this, it is critical to perform immunocytochemistry on formalin-fixed cell-block sections only. In addition, unless the interpretation criteria for immunohistochemical evaluation of effusion fluids are not modified specifically, it may not be productive in resolving some challenging cases. However, this aspect is not well elaborated in the literature. A basic and critical challenge is finding and locating the cells of interest in cell-block sections of effusion fluids. A unique approach is to choose a fundamental immunopanel which highlight the mesothelial and inflammatory cells in reactive effusion fluids to create the basic map. This allows detection of a 'second-foreign' population which can be immunocharacterized further with the help of subtractive coordinate immunoreactivity pattern (SCIP) approach elaborated here.

Evaluation of DNA/RNA quality from cell block of malignant mesothelioma and lung adenocarcinoma

Malignant mesothelioma (MM) is a rare and highly lethal tumor that arises from mesothelial tissue on the surface of the chest and abdominal cavity. Cytological examination of body fluids, including pleural fluid and ascites, is essential for the differentiation of malignant mesothelioma from other carcinomas, such as lung and gastrointestinal carcinomas and metastatic tumors. To evaluate the effectiveness of cell block preparation procedures, which are used for immunocytochemical staining and genetic panel analysis of tumor-specific gene mutations, we used various fixatives. We also evaluated the effects of immunostaining, and the quality of nucleic acids for genetic analysis.

METHODS

Cell blocks were prepared using the malignant mesothelioma cell lines MESO4 and H226 and non-small cell lung carcinoma cell line HCC78. The cells were fixed using 10% neutral buffered formalin and four different fixatives for liquid cytology. Fixed cells were formed into cell clusters using sodium alginate or centrifugation, and paraffin-embedded cell blocks were prepared.

RESULTS

Cell blocks were morphologically evaluated by hematoxylin and eosin and immunocytological staining, and the nucleic acid quality was evaluated by DNA/RNA extraction, qPCR, and next-generation sequence analysis. D2-40 and WT1 staining differed depending on the fixation solution and the cell cluster formation method; however, the degree of nucleic acid degradation was not impaired by any method.

CONCLUSION

Although the morphological evaluation of cytology specimens is affected by the method of cell block preparation, it is still useful for nucleic acid extraction and gene panel analysis, as long as there are sufficient amounts of tumor cells.

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.

Utility of a limited panel of calretinin and Ber-EP4 immunocytochemistry on cytospin preparation of serous effusions: A cost-effective measure in resource-limited settings

Background:

Differentiation between reactive, but morphologically atypical, mesothelial cells and adenocarcinoma in effusions can be problematic. Elaborate immunohistochemical panels have been devised. Techniques like DNA analysis, flow/image cytometry, and K-ras mutation analysis are research oriented and difficult to perform in routine, especially in resource-poor centers. We evaluated the efficacy of a limited two-antibody panel comprising calretinin and Ber-EP4 on cytospin and cell block preparations, in 100 effusion samples.

Materials and Methods:

Fifty cases of reactive mesothelial hyperplasia and 50 cases of adenocarcinoma diagnosed by cytomorphology in ascitic/pleural fluid specimens over a 2-year period were assessed. The diagnoses were confirmed by clinical/histopathologic correlation. Cytospin smears were made in all. Cell blocks were prepared, wherever adequate fluid was available. Immunocytochemistry (ICC) for calretinin and Ber-EP4 was performed.

Results:

Forty-five of the reactive effusion cases (90%) were calretinin reactive and Ber-EP4 negative. Among the adenocarcinoma cases, 49 (98%) were calretinin negative but Ber-EP4 positive. Thus, both calretinin and Ber-EP4 had a high sensitivity (90% and 98%, respectively), as well as a high specificity (100% and 86%, respectively). In the 21 reactive mesothelial cases, whose cell blocks were made, results were comparable to those on cytospin. However, of the 19 adenocarcinoma cases in which cell blocks were prepared, all were Ber-EP4 immunopositive except for three, which were positive on cytospin, implying false-negative results on cell blocks.

Conclusions:

A limited panel of two monoclonal antibodies, calretinin and Ber-EP4, may be useful in cytology, as a “primary antibody panel”, for accurate diagnosis and patient management. Additionally, ICC can be performed easily on cytospin preparations, which gave results comparable to cell blocks in our study.

Challenges in the interpretation of peritoneal cytologic specimens

CONTEXT

The presence of malignant cells in peritoneal washings leads to classification as International Federation of Gynecology and Obstetrics stage IC or higher in ovarian carcinomas and at least International Federation of Gynecology and Obstetrics stage IIIA in endometrial carcinomas. Unfortunately, the morphologic examination of cytologic specimens has not proven to be a sensitive or specific diagnostic tool. Malignant cells might be few in number and might be unrecognized among a large population of mesothelial cells and/or macrophages, or reactive mesothelial cells might be misinterpreted as neoplastic cells leading to unnecessary chemotherapy.

OBJECTIVE

To evaluate the main pitfalls in the evaluation of peritoneal washings in patients with gynecologic malignancies and analyze the ancillary studies that might be helpful to achieve the correct diagnosis with an emphasis on immunocytochemistry.

DATA SOURCES

A comprehensive review of the literature was performed.

CONCLUSIONS

Peritoneal effusions may represent major challenges to the pathologist and can have important clinical implications. Immunostains for epithelial markers such as B72.3, MOC-31, and Ber-EP4 represent the best available markers to identify epithelial cells. Caution is advised to not overdiagnose endometriosis or endosalpingiosis as adenocarcinoma.

[Immunocytochemistry in malignant serous effusions]

Immunocytochemistry may be of valuable help in typing most malignant serous effusions. Various preparatory methods are described including centrifugation and smearing, cytocentrifugation, cell blocks and liquid based cytology. The value and usefulness of immunocytochemistry depends on the experience of each pathologist. The use of a panel of antibodies associating markers of carcinomas with markers of mesothelial cells is recommended.

The diagnostic utility of immunohistochemistry in distinguishing between epithelioid mesotheliomas and squamous carcinomas of the lung: a comparative study

As both mesotheliomas and squamous carcinomas can present a wide variety of morphological patterns, they can on occasion be confused. Recently, some groups of investigators have called attention to the difficulties that sometimes exist in distinguishing between these malignancies and the need to define a panel of markers that can assist in reaching the correct diagnosis. The aim of the present study is to compare the value of the various immunohistochemical markers currently available for the diagnosis of mesothelioma and squamous carcinoma of the lung. A total of 30 epithelioid pleural mesotheliomas exhibiting a solid or predominantly solid pattern, and 30 nonkeratinizing squamous carcinomas of the lung were investigated for the expression of the following markers: podoplanin, calretinin, mesothelin, WT1, keratin 5/6, keratin 7, p63, carcinoembryonic antigen (CEA), MOC-31, Ber-EP4, B72.3, BG-8 (Lewis(y)), leu-M1 (CD15), and thyroid transcription factor-1 (TTF-1). All 30 (100%) of the mesotheliomas reacted for calretinin, mesothelin and keratin 7, 93% each for podoplanin, WT1 and keratin 5/6, 13% for Ber-EP4, 7% each for p63, MOC-31 and BG-8, and 0% for B72.3, CEA, leu-M1 and TTF-1. All 30 (100%) of the squamous carcinomas were positive for p63 and keratin 5/6, 97% for MOC-31, 87% for Ber-EP4, 80% for BG-8, 77% for CEA, 57% for keratin 7, 40% for calretinin and B72.3, 30% for leu-M1, 27% for mesothelin, 15% for podoplanin, and 0% for WT 1 and TTF-1. After analyzing the results, it is concluded that from a practical point-of-view, a combination of two positive mesothelioma markers (WT1 and calretinin or mesothelin) with two negative mesothelioma markers (p63 and MOC-31) would allow the differential diagnosis to be established between epithelioid mesotheliomas and squamous carcinomas of the lung in nearly all instances.

Value of immunohistochemistry in distinguishing peritoneal mesothelioma from serous carcinoma of the ovary and peritoneum: a review and update

At present, a large number of immunohistochemical markers that can be used in the differential diagnosis between epithelioid peritoneal mesotheliomas and serous carcinomas are available. However, great differences of opinion exist regarding the individual value of some of these markers. This article provides a critical review of all of the information that is currently available on those markers that have the greatest potential for assisting in distinguishing between peritoneal mesotheliomas and serous carcinomas. The conclusion of this review indicates that the positive serous carcinoma markers, by and large, have a higher degree of sensitivity and specificity in assisting in discriminating between these malignancies than the positive mesothelioma markers. From a practical point of view, a combination of MOC-31 (or Ber-EP4), estrogen receptors, and calretinin immunostaining should allow a clear distinction to be made between epithelioid peritoneal mesotheliomas and serous carcinomas in most cases.

The diagnostic utility of immunohistochemistry in distinguishing between mesothelioma and renal cell carcinoma: A comparative study

Both mesotheliomas and renal cell carcinomas can present a wide variety of morphological patterns. Because of this, renal cell carcinomas that metastasize to the pleura and lung may be confused with mesotheliomas. The aim of the present study was to compare the value of the various immunohistochemical markers currently available for the diagnosis of mesothelioma and renal cell carcinoma. A total of 48 mesotheliomas (40 epithelioid, 8 sarcomatoid), and 48 renal cell carcinomas (24 conventional, 12 chromophobe, 8 papillary, 4 sarcomatoid) were investigated for the expression of the following markers: calretinin, mesothelin, cytokeratin 5/6, WT1, thrombomodulin (TM), N-cadherin, CD15 (leu-M1), MOC-31, Ber-EP4, BG-8 (Lewis(y)), CD10, renal cell carcinoma marker (RCC Ma), carcinoembryonic antigen (CEA), and B72.3. All (100%) of the epithelioid mesotheliomas reacted for calretinin, mesothelin, and cytokeratin 5/6; 93% for WT1; 78% for TM; 75% for N-cadherin, 48% for CD10, 15% for Ber-EP4, 8% for MOC-31, 8% for RCC Ma, 5% for BG-8, and none for CEA, B72.3, or CD15. Of the sarcomatoid mesotheliomas, 88% expressed calretinin, 75% N-cadherin, 38% CD10, and 13% each expressed cytokeratin 5/6, WT1, and TM. All of the remaining markers were negative. Among the RCCs, 81% expressed CD10, 75% N-cadherin, 63% CD15, 50% RCC Ma, 50% MOC-31, 42% Ber-EP4, 8% BG-8, and 2% TM. The remaining markers were negative. The results indicate that calretinin, mesothelin, and cytokeratin 5/6 are the best positive mesothelioma markers for differentiating epithelioid mesotheliomas from renal cell carcinomas. The best discriminators among the antibodies considered negative markers for mesothelioma are CD15, MOC-31, and RCC Ma. An accurate differential diagnosis can be reached with the use of any 2 of the 3 recommended positive markers, which should be selected based on availability and on which ones yield the best staining results in a given laboratory. One of the recommended negative markers may be added to the panel if deemed necessary. If confirmation of renal origin is needed, RCC Ma could be useful. Calretinin is the only marker that appears to have any utility in distinguishing between sarcomatoid mesotheliomas and sarcomatoid renal cell carcinomas.

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.

Pseudomesotheliomatous angiosarcoma of the chest wall and pleura

Angiosarcoma is a rare soft tissue sarcoma that usually occurs in deep soft tissues, breast, spleen, liver, and bone. Primary thoracic parietal localization of angiosarcoma is rare and prognosis is poor. In this report, we present the CT and PET features of a patient with pseudomesotheliomatous angiosarcoma of the chest wall and pleura, which, to the best of our knowledge, have not previously been described.

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.

AP2-like cis element is required for calretinin gene promoter activity in cells of neuronal phenotype differentiated from multipotent human cell line DEV

Calretinin (CR) is an EF-hand calcium binding protein expressed at high level in neurons. To identify regulatory elements in CR gene promoter, cultured rat cortical cells were transfected with constructs containing its 5'-end deletion mutants and the luciferase reporter gene. A fragment ending at -115 bp upstream of the transcription start site had high promoter activity and was able to induce expression of luciferase specifically in neuronal cells of cortical cultures. The wild type sequence of -115/+54 CR promoter fragment preferentially drove the expression of green fluorescent protein analog in cells of neuronal phenotype differentiated from multipotent human cell line DEV. Electrophoretic mobility shift assays (EMSA) revealed that the -115/-71 CR gene promoter region contains a binding site for a factor present in brain nuclear extract. Among oligonucleotides containing consensus binding sites for transcription factors within this region, the one representing AP2 binding site was able to compete formation of a protein complex. Mutations of this site prevented the binding between brain protein(s) and the -115/+54 CR gene promoter region and abolished the preferential expression of reporter gene in neuronal cells of DEV line. Thus, the AP2-like element seems to be essential for the neuron-specific activity of the CR gene promoter.

The value of Wilms tumor susceptibility gene 1 in cytologic preparations as a marker for malignant mesothelioma

BACKGROUND

It has been shown that detection of the Wilms tumor susceptibility gene 1 protein (WT1) has diagnostic utility in the distinction of mesothelioma from adenocarcinoma in tissue sections of pleural tumors. This immunohistochemical study evaluates the effectiveness of WT1 as a marker for malignant mesothelioma in paraffin sections of cell block preparations derived from effusion specimens.

METHODS

The authors evaluated 111 cell blocks for WT1 immunoreactivity, including 14 mesotheliomas and 97 metastatic adenocarcinomas from various sites.

RESULTS

Nuclear reactivity for WT1 was observed in all samples of mesothelioma. However, only 22 of 97 samples (23%) of metastatic adenocarcinoma, nearly all of which were of ovarian origin (91%), exhibited nuclear reactivity for WT1. In 14 other samples (most of pulmonary derivation), WT1 staining restricted to the cytoplasm was observed for some tumor cells and was regarded as nonspecific.

CONCLUSIONS

Based on this staining profile, WT1 represents an effective marker for mesotheliomas in cell block preparations and can aid in its distinction from pulmonary adenocarcinoma. In assessment of effusion specimens with metastatic carcinoma, nuclear reactivity for WT1 is highly suggestive of an ovary primary tumor

Comparison of antibodies to HBME-1 and calretinin for the detection of mesothelial cells in effusion cytology

The distinction of mesothelial cells in cytologic samples is often a diagnostic challenge. This is particularly true in potentially malignant effusions in which reactive mesothelial cells may simulate adenocarcinoma (ACA) cells, and in the differentiation of ACA vs. mesothelioma. We sought to determine the superior antibody for the positive identification of mesothelial cells in these circumstances. Cell block sections of 25 reactive and 8 malignant mesothelioma effusions were immunostained with an avidin-biotin procedure, using antibodies to HBME-1 and calretinin. No pretreatment of samples was necessary for the HBME-1-stained slides; microwave antigen retrieval was performed on all slides stained for calretinin. A negative control was performed on each sample. The staining intensity of tumor cells was scored on a scale of 0-3+, with the proportion of immunoreactive cells categorized as <25%, 25-50%, 50-75%, and >75%. The predominant staining pattern for HBME-1 was surface, with rare samples also exhibiting cytoplasmic staining as well. The calretinin-staining pattern was cytoplasmic, with peripheral condensation/prominence and accompanying nuclear staining. All samples were immunoreactive with both antibodies. Fifty-five percent (18/33) of samples showed significantly stronger immunoreactivity with calretinin than with HBME-1; 45% (15/33) of samples showed equivalent staining with the two markers. None of the samples in this study showed stronger immunoreactivity with HBME-1 than with calretinin. Sixty-one percent (20/33) of samples stained with HBME-1 at a moderate (2+) intensity. Fifty-five percent (18/33) of samples stained with calretinin at a strong (3+) intensity. While only 12% of samples showed >75% immunoreactivity for HBME-1, 58% of samples showed >75% of cells immunoreactive for calretinin. Calretinin is the preferred marker in identifying mesothelial cells in cytologic samples, showing the highest sensitivity for mesothelial cells, as evidenced by a more intense staining reaction in a higher percentage of cells than with HBME-1. Published 2001 Wiley-Liss, Inc.