Electron microscopy in tumor diagnosis: indications for its use in the immunohistochemical era

Tumor biomarkers for diagnosis, prognosis and targeted therapy

Tumor biomarkers, the substances which are produced by tumors or the body's responses to tumors during tumorigenesis and progression, have been demonstrated to possess critical and encouraging value in screening and early diagnosis, prognosis prediction, recurrence detection, and therapeutic efficacy monitoring of cancers. Over the past decades, continuous progress has been made in exploring and discovering novel, sensitive, specific, and accurate tumor biomarkers, which has significantly promoted personalized medicine and improved the outcomes of cancer patients, especially advances in molecular biology technologies developed for the detection of tumor biomarkers. Herein, we summarize the discovery and development of tumor biomarkers, including the history of tumor biomarkers, the conventional and innovative technologies used for biomarker discovery and detection, the classification of tumor biomarkers based on tissue origins, and the application of tumor biomarkers in clinical cancer management. In particular, we highlight the recent advancements in biomarker-based anticancer-targeted therapies which are emerging as breakthroughs and promising cancer therapeutic strategies. We also discuss limitations and challenges that need to be addressed and provide insights and perspectives to turn challenges into opportunities in this field. Collectively, the discovery and application of multiple tumor biomarkers emphasized in this review may provide guidance on improved precision medicine, broaden horizons in future research directions, and expedite the clinical classification of cancer patients according to their molecular biomarkers rather than organs of origin.

Qualitative disorder measurements from backscattering spectra through an optical fiber

In the processes related to the development of cancer, there are different genetic and epigenetic events involved that result in structural changes of the affected cells. In the early stages of the disease, these changes occur at the nanoscale, remaining undetectable by conventional light microscopy, due to diffraction-limited resolution (∼250 - 550 nm). In this sense, a technique termed partial wave spectroscopy (PWS) allows the detection of these nanostructural changes by measuring a statistical parameter called disorder strength (L _d ). PWS uses a combination of a tunable filter and a camera to acquire the backscattering spectra for each pixel on the image. In this paper, we study and validate the possibility of obtaining a qualitative measurement of the disorder using the spectrum of the averaged spatial information. Instead of using spatial information and measuring sequentially spectral ranges, we measure the backscattered signal gathered by an optical fiber by means of a spectrograph. This will allow this method to be applied in systems where it is not possible to acquire a complete high resolution image for many spectral bands, while significantly enhancing speed.

Undifferentiated sinonasal malignant melanoma: A case report

Undifferentiated sinonasal malignant melanoma (MM) is a rare type of tumor, which can be easily misdiagnosed. The present study reports a 41-year-old male patient who presented with a 4-day history of epistaxis. Clinical examination and radiological imaging lead to the detection of a mass in the right sinonasal region. Histopathological examination revealed that the mass was composed of malignant epithelioid cells arranged in nests and sheets. These cells displayed a hemangiopericytoma-like pattern with antler-like branching vessels. Immunohistochemical staining revealed that the tumor cells exhibited negative expression of melanocytic markers. This increased the difficulty of distinguishing undifferentiated MM from other malignant tumors located in the sinonasal area, particularly undifferentiated nasopharyngeal carcinoma. The diagnosis of undifferentiated MM was determined by ultrastructures, including the mature melanosomes and premelanosomes, in tumor cells by transmission electron microscopy. The present study suggests that the analysis of cancer stem cell marker and vasculogenic mimicry may be an important auxiliary tool for the diagnosis of MM.

[What is new in 2010 for electron microscopy in surgical pathology?]

Différentes méthodes complémentaires permettant d’optimiser le diagnostic et le pronostic des lésions observées dans un laboratoire d’anatomopathologie ont permis, ces dernières années, d’améliorer considérablement l’offre de soins aux patients. Ces méthodes correspondent essentiellement aux techniques d’immuno-histochimie et de biologie moléculaire. La place d’une autre technique autrefois largement utilisée en anatomopathologie, la microscopie électronique (ME), est à l’inverse de plus en plus restreinte. La ME est une méthode longue, difficile, onéreuse, nécessitant un personnel hautement qualifié. Elle est de moins en moins implantée dans un laboratoire de pathologie et devient surtout réservée à des centres universitaires et de recherche. Toutefois, la ME reste un outil indispensable pour le pathologiste. En effet, elle permet parfois de confirmer, et plus exceptionnellement de poser, le diagnostic de certaines lésions tissulaires et cellulaires observées en pathologie humaine. La ME est aussi d’un apport très important pour la compréhension de la physiopathologie de certaines maladies humaines émergentes, notamment d’origine infectieuse. Nous abordons dans cette revue les principales indications actuelles de la ME, en insistant sur certains domaines de la pathologie humaine, comme les maladies infectieuses et certaines tumeurs.

Extrathoracic Mesothelial Proliferations and Their Mimics

Mesothelial proliferations, either reactive or neoplastic in nature, often pose difficult diagnostic dilemmas. Electron microscopy continues to be a gold standard in the identification of mesothelial differentiation. However, it is very common to apply long panels of antibodies for that purpose. In most cases, light microscopy and immunohistochemistry will solve the problem. However, the definitive, specific, and sensitive immunohistochemical marker is still lacking. This is particularly true in peritoneal and testicular mesothelial tumors, in which common embryologic origin with epithelial elements results in overlapping immunohistochemistry and morphology. The particularities of peritoneal and testicular mesothelial proliferations, and the main tumors that may mimic them in these sites, as well as the value and limitations of immunohistochemistry and electron microscopy in their differential diagnosis are the subject of this review.

The high post-test probability of a cytological examination renders further investigations to establish a diagnosis of epithelial malignant pleural mesothelioma redundant

The aim of the study was to establish in a prospective and blinded manner the diagnostic yield of morphology, immunocytochemistry (ICH) and electron microscopy (EM) in the cytological analysis of malignant pleural mesothelioma (MPM). Pleural fluid from consecutive patients, 14 with a histologically proven MPM, 12 with a malignant pleuritis due to adenocarcinoma (AC), and 13 with a reactive pleural effusion (RM), was separately analyzed. Smears were incubated with monoclonal antibodies (Tag72, Ber-Ep4, anti-CEA, EMA). These were considered suggestive for MPM when only EMA stained positive, for AC when three out of four markers stained positive, and for RM when no marker stained positive. The post-test probability of the morphological, ICH, and EM analysis were 92, 100, 92% or MPM, 91, 100, 86% for AC, and 88, 88, 90% for RM, respectively. We concluded that the high post-test probability of a combined morphological and ICH diagnosis of MPM warrants to cease further diagnostic procedures in these patients. Electron microscopy did not add to accuracy of diagnosis.

The comparative roles of electron microscopy and immunohistochemistry in the diagnosis of soft tissue tumours

Electron microscopy has contributed to the diagnosis of soft tissue tumours for four decades, and immunohistochemistry for two. Because of its relative ease of use and interpretation, the latter technique has become extensively and routinely applied to identify lines of differentiation in benign soft tissue tumours and in sarcomas. The use of electron microscopy has declined but retains a role because few antibodies are wholly specific or fully sensitive, some tumours are polyphenotypic or divergent in differentiation, and others have no specific antigens. Immunohistochemistry is superior in diagnosis of smooth muscle tumours, small round cell tumours, sarcomas with epithelioid morphology, and most synovial sarcomas. Electron microscopy is of particular value for peripheral nerve sheath tumours, marker-negative synovial sarcomas, pleomorphic sarcomas and mesotheliomas. As with all adjunctive techniques, immunohistochemistry and electron microscopy should be used in a complementary fashion according to the nature of the diagnostic problem.

Establishment of permanent cell lines purified from human mesothelioma: morphological aspects, new marker expression and karyotypic analysis

This study reports the establishment of three major subtypes of human mesothelioma cells in tissue culture, i.e. the epithelioid, sarcomatoid and biphasic forms, and compares their phenotypic and biological characteristics. Primary cells isolated from biopsies or pleural exudates were subcultured for over 50 passages. We evaluated immunoreactivity using various mesothelial markers related to histological patterns of these cell lines. For epithelioid cells, calretinin and cytokeratin were found to be useful and easily interpretable markers as for control mesothelial cells. The biphasic form was only partially positive and the sarcomatoid type negative. Vimentin was expressed by all cell lines. BerEP4, a specific marker for adenocarcinoma, was negative. Interestingly, while the macrophage marker CD14 was negative, immunoreactivity for a mature macrophage marker (CD68) was expressed by all cell types, suggesting that this marker might constitute an additional tool useful in the differential diagnosis of mesothelioma. At the ultrastructural level, a cell surface rich in microvilli confirmed their mesothelial origin. PCR analysis revealed that none of the cell lines contained SV40 DNA. Karyotypic analyses showed more complex abnormalities in the epithelioid subtype than in the sarcomatoid form. These cell lines may be useful in the study of cellular, molecular and genetic aspects of the disease.

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.

Electron microscopy in pathology articles: a retrospective appraisal

Electron microscopy (EM) is a valuable standard tool in basic research and teaching. However, its use in diagnosis is limited, either for strategic reasons or budgetary constraints. This means that its many potential applications are more often neglected, either as an ancillary tool, quality control method, or gold standard, to complement, support, or confirm results of pathological studies. To evaluate the use of EM in this setting, the authors analyzed all articles (n = 2,531) in the three top indexed diagnostic pathology journals for a period of 60 months from July 1993 to June 1998. A total of 448 articles in which the use of EM was indicated, according to standard surgical pathology textbooks, were selected. Both the actual and the potential EM content of each article were scored, as follows: zero, illustrative, supportive, gold standard (for confirmation of research results), extensive, and predominant. Of the total number of articles in which EM was indicated, 77% made use of the technique. EM support was lacking most frequently in articles on serosal neoplasms and on new diagnostic strategies (p < .00005). There was no definite trend toward an increase or decrease in the use of EM during the period analyzed. The authors conclude that EM is used in most reports on diagnostic pathology, when it is indicated. However, a small but non-negligible percentage of articles (23%) could benefit from including EM as an ancillary, control, or gold standard method to complement, support, or confirm their results.

Electron microscopy in tumour diagnosis: continuing to complement other diagnostic techniques

The histopathological diagnosis of tumours has been transformed by immunohistochemistry. Used with experience and judgement, a panel of antibodies or antisera, combined when necessary with antigen retrieval, will enable the accurate typing of most problematic tumours. This has led many histopathologists to question whether the electron microscope has any residual utility for tumour diagnosis; the machines are large, costly to purchase and maintain, and will accept only minute samples of tissue. The following articles by Mierau and by Eyden, both strong advocates, comment on the current and future role of electron microscopy in tumour diagnosis.

Electron microscopy for tumour diagnosis: is it redundant?

The histopathological diagnosis of tumours has been transformed by immunohistochemistry. Used with experience and judgement, a panel of antibodies or antisera, combined when necessary with antigen retrieval, will enable the accurate typing of most problematic tumours. This has led many histopathologists to question whether the electron microscope has any residual utility for tumour diagnosis; the machines are large, costly to purchase and maintain, and will accept only minute samples of tissue. The following articles by Mierau and by Eyden, both strong advocates, comment on the current and future role of electron microscopy in tumour diagnosis.