[A new one in the lung and pleura neoplasms classification (WHO, 2021, 5th edition)]

The article contains an overview of the new WHO classification of thoracic tumors (2021). As in the previous edition of 2015, considerable attention is paid to neoplasms of the lungs and pleura. The article presents current data on molecular genetic features and morphological manifestations of a number of new lung tumors, with a detailed histological and immunohistochemical data. Thoracis undifferentiated tumor with SMARCA4 deficiency and bronchiolar adenoma are described. Emphasis is placed on the algorithms of morphological diagnostics, including a complete description of the tumor and facilitating the study in the practice of a pathologist. The main morphological criteria of mesothelial tumors of the pleura are given; describes in detail the procedure for assessing the degree of malignancy of diffuse epithelioid pleural mesothelioma and non-mucinous lung adenocarcinomas.

The use of a next-generation sequencing-derived machine-learning risk-prediction model (OncoCast-MPM) for malignant pleural mesothelioma: a retrospective study

BACKGROUND

Current risk stratification for patients with malignant pleural mesothelioma based on disease stage and histology is inadequate. For some individuals with early-stage epithelioid tumours, a good prognosis by current guidelines can progress rapidly; for others with advanced sarcomatoid cancers, a poor prognosis can progress slowly. Therefore, we aimed to develop and validate a machine-learning tool-known as OncoCast-MPM-that could create a model for patient prognosis.

METHODS

We did a retrospective study looking at malignant pleural mesothelioma tumours using next-generation sequencing from the Memorial Sloan Kettering Cancer Center-Integrated Mutation Profiling of Actionable Cancer Targets (MSK-IMPACT). We collected clinical, pathological, and routine next-generation sequencing data from consecutive patients with malignant pleural mesothelioma treated at the Memorial Sloan Kettering Cancer Center (New York, NY, USA), as well as the MSK-IMPACT data. Together, these data comprised the MSK-IMPACT cohort. Using OncoCast-MPM, an open-source, web-accessible, machine-learning risk-prediction model, we integrated available data to create risk scores that stratified patients into low-risk and high-risk groups. Risk stratification of the MSK-IMPACT cohort was then validated using publicly available malignant pleural mesothelioma data from The Cancer Genome Atlas (ie, the TCGA cohort).

FINDINGS

Between Feb 15, 2014, and Jan 28, 2019, we collected MSK-IMPACT data from the tumour tissue of 194 patients in the MSK-IMPACT cohort. The median overall survival was higher in the low-risk group than in the high-risk group as determined by OncoCast-MPM (30·8 months [95% CI 22·7-36·2] vs 13·9 months [10·7-18·0]; hazard ratio [HR] 3·0 [95% CI 2·0-4·5]; p<0·0001). No single factor or gene alteration drove risk differentiation. OncoCast-MPM was validated against the TCGA cohort, which consisted of 74 patients. The median overall survival was higher in the low-risk group than in the high-risk group (23·6 months [95% CI 15·1-28·4] vs 13·6 months [9·8-17·9]; HR 2·3 [95% CI 1·3-3·8]; p=0·0019). Although stage-based risk stratification was unable to differentiate survival among risk groups at 3 years in the MSK-IMPACT cohort (31% for early-stage disease vs 30% for advanced-stage disease; p=0·90), the OncoCast-MPM-derived 3-year survival was significantly higher in the low-risk group than in the high-risk group (40% vs 7%; p=0·0052).

INTERPRETATION

OncoCast-MPM generated accurate, individual patient-level risk assessment scores. After prospective validation with the TCGA cohort, OncoCast-MPM might offer new opportunities for enhanced risk stratification of patients with malignant pleural mesothelioma in clinical trials and drug development.

FUNDING

US National Institutes of Health/National Cancer Institute.

[Morphological diagnostics of malignant pleural mesothelioma]

The World Health Organization (WHO) classification differentiates between pleural tumors of mesothelial and mesenchymal origin as well as lymphoproliferative disorders, with malignant mesotheliomas forming the most common pleural primary tumor. Histologically, epithelioid (40-60 %), sarcomatoid (20-40 %), and biphasic mesotheliomas (20-40 %) are distinguished. The certain morphological diagnosis of a malignant pleural mesothelioma requires the establishment of mesothelial differentiation by means of an appropriate panel of antibodies to exclude pleural dissemination of a pulmonary or extrapulmonary epithelial malignancy and also requires the establishment of at least focal invasive growth to distinguish from reactive mesothelial proliferation. The exclusion of a malignant pleural mesothelioma may induce further differential diagnostic considerations, e. g. concerning the assignment to a certain primary tumor after the establishment of carcinomatous pleuritis.

Malignant Pleural Mesothelioma : Rationale for a New TNM Classification

BACKGROUND

Malignant pleural mesothelioma (MPM) is a rare but aggressive thoracic malignancy with a poor prognosis. In this regard, a well-defined staging system is of utmost importance in order to correctly diagnose and assign an appropriate treatment to the patient.

METHODS

The current TNM-staging system (7th edition) enables to either clinically or pathologically stage the severity of the disease according to extension of the tumor (T), number of nodes (N) and presence of metastases (M). Patients with stage I-III are considered for surgery, while palliative treatment is indicated for stage IV patients according to the current classification.

RESULTS

Despite its widespread use, the validity of this staging system is questioned due to the low prevalence, histological variety and retrospective nature of the previous study design. In addition, the role of specific treatment modalities including surgery, has yet to be determined, especially for treatment of early-stage disease. In this regard, the International Association for the Study of Lung Cancer (IASLC) initiated the multi-centre, prospective "Mesothelioma Staging Project" in order to address limitations of the 7th edition and to optimize the staging system in accordance to current needs.

CONCLUSIONS

An improved staging system will contribute to the design of prospective multi-institutional clinical trials investigating novel treatment strategies for mesothelioma. In this way comparison of outcome between different medical centres also becomes feasible.

Active symptom control with or without chemotherapy in the treatment of patients with malignant pleural mesothelioma (MS01): a multicentre randomised trial

BACKGROUND

Malignant pleural mesothelioma is almost always fatal, and few treatment options are available. Although active symptom control (ASC) has been recommended for the management of this disease, no consensus exists for the role of chemotherapy. We investigated whether the addition of chemotherapy to ASC improved survival and quality of life.

METHODS

409 patients with malignant pleural mesothelioma, from 76 centres in the UK and two in Australia, were randomly assigned to ASC alone (treatment could include steroids, analgesic drugs, bronchodilators, palliative radiotherapy [n=136]); to ASC plus MVP (four cycles of mitomycin 6 mg/m2, vinblastine 6 mg/m2, and cisplatin 50 mg/m2 every 3 weeks [n=137]); or to ASC plus vinorelbine (one injection of vinorelbine 30 mg/m2 every week for 12 weeks [n=136]). Randomisation was done by minimisation, with stratification for WHO performance status, histology, and centre. Follow-up was every 3 weeks to 21 weeks after randomisation, and every 8 weeks thereafter. Because of slow accrual, the two chemotherapy groups were combined and compared with ASC alone for the primary outcome of overall survival. Analysis was by intention to treat. This study is registered, number ISRCTN54469112.

FINDINGS

At the time of analysis, 393 (96%) patients had died (ASC 132 [97%], ASC plus MVP 132 [96%], ASC plus vinorelbine 129 [95%]). Compared with ASC alone, we noted a small, non-significant survival benefit for ASC plus chemotherapy (hazard ratio [HR] 0.89 [95% CI 0.72-1.10]; p=0.29). Median survival was 7.6 months in the ASC alone group and 8.5 months in the ASC plus chemotherapy group. Exploratory analyses suggested a survival advantage for ASC plus vinorelbine compared with ASC alone (HR 0.80 [0.63-1.02]; p=0.08), with a median survival of 9.5 months. There was no evidence of a survival benefit with ASC plus MVP (HR 0.99 [0.78-1.27]; p=0.95). We observed no between-group differences in four predefined quality-of-life subscales (physical functioning, pain, dyspnoea, and global health status) at any of the assessments in the first 6 months.

INTERPRETATION

The addition of chemotherapy to ASC offers no significant benefits in terms of overall survival or quality of life. However, exploratory analyses suggested that vinorelbine merits further investigation.

Cell membrane reactivity of MIB-1 antibody to Ki67 in human tumors: fact or artifact?

Ki67 immunohistochemistry is a widely used marker of the tumor proliferative fraction. Apart from the nuclear staining of dividing cells, MIB-1 monoclonal antibody was also found to stain the cell membrane of some tumor types. Indeed, such membrane reactivity was proposed as a diagnostic feature of hyalinizing trabecular tumor (HTT) of the thyroid. To verify the diagnostic role of Ki67 membrane pattern, 6 HTTs, 8 pulmonary sclerosing hemangiomas (SH), and 6 other human tumors with MIB-1 cell membrane immunoreactivity were stained by immunoperoxidase with 5 different anti-Ki67 antibodies in different experimental conditions. We show here that the cell membrane reactivity reported in HTT is produced only by MIB-1 and not by other antibodies to Ki67 (including commercially available mouse and rabbit monoclonal antibodies). In addition, this peculiar pattern is obtained only if the reaction is performed at room temperature, because automated immunostainers which operate at 37 degrees C do not produce any MIB-1 membrane localization. The same findings were obtained in the other 6 tumors. Conversely, sclerosing hemangioma of the lung did not produce any MIB-1 cell membrane reactivity in our hands. A cross-reactivity of the MIB-1 monoclonal antibody with an epitope expressed at the cell membrane level (rather than an artifact) seems the most likely explanation for this finding, because the immunoreactivity is generally intense and uniform in the membrane positive tumors. We conclude that when Ki67 immunohistochemistry is used for diagnostic purposes in a suspected HTT, only MIB-1 clone at room temperature should be employed.

Lymphomas involving the pleura: a clinicopathologic study of 34 cases diagnosed by pleural biopsy

CONTEXT

Pleural involvement by lymphoma is relatively common. However, there are very few clinicopathologic studies reported in the literature of lymphomas involving the pleura.

OBJECTIVE

To characterize the clinicopathologic features of lymphomas involving the pleura.

DESIGN

We reviewed the clinicopathologic features of 34 patients with lymphoma involving the pleura proven by biopsy and classified these neoplasms using the World Health Organization classification.

RESULTS

There were 22 men and 12 women, with an average age of 62 years (range, 22-82 years). Nine (26.5%) patients had pleural involvement as the only site of disease, 22 (64.7%) had other sites of involvement, and 3 (8.8%) had inadequate staging data. Eighteen (56.2%) of 32 patients with adequate clinical data had a history of lymphoma (including 3 patients with pleural involvement as the only disease site). In 29 (85.3%) cases, a specific diagnosis according to the World Health Organization classification could be made: 17 (58.6%) diffuse large B-cell lymphoma, 5 (17.2%) follicular lymphoma (including a case with areas of diffuse large B-cell lymphoma), 2 (6.9%) small lymphocytic lymphomas/chronic lymphocytic leukemia, 2 (6.9%) precursor T-cell lymphoblastic lymphoma/leukemia, 1 (3.4%) mantle cell lymphoma, 1 (3.4%) posttransplant lymphoproliferative disorder, and 1 (3.4%) classical Hodgkin lymphoma. The other 5 cases were B-cell lymphomas that could not be further classified. Cytologic examination of pleural fluid was performed in 15 cases and was positive for lymphoma in 8 (53.3%) cases.

CONCLUSIONS

Most patients with lymphoma involving the pleura have simultaneous evidence of systemic involvement. The most frequent type is diffuse large B-cell lymphoma, followed by follicular lymphoma. Cytologic examination can have negative results in patients with pleural involvement by lymphoma.

Review and update of uncommon primary pleural tumors: a practical approach to diagnosis

OBJECTIVE

We address the current classifications and new changes regarding uncommon primary pleural tumors. Primary pleural tumors are divided according to their behavior and are discussed separately as benign tumors, tumors of low malignant potential, and malignant neoplasms.

DATA SOURCES

Current literature concerning primary pleural neoplasms was collected and reviewed.

STUDY SELECTION

Studies emphasizing clinical, radiological, or pathologic findings of primary pleural neoplasms were obtained.

DATA EXTRACTION

Data deemed helpful to the general surgical pathologist when confronted with an uncommon primary pleural tumor was included in this review.

DATA SYNTHESIS

Tumors are discussed in 3 broad categories: (1) benign, (2) low malignant potential, and (3) malignant. A practical approach to the diagnosis of these neoplasms in surgical pathology specimens is offered. The differential diagnosis, including metastatic pleural neoplasms, is also briefly addressed.

CONCLUSIONS

Uncommon primary pleural neoplasms may mimic each other, as well as mimic metastatic cancers to the pleura and diffuse malignant mesothelioma. Correct diagnosis is important because of different prognosis and treatment implications for the various neoplasms.

Evaluation of semiautomated measurements of mesothelioma tumor thickness on CT scans

RATIONALE AND OBJECTIVES

To evaluate the clinical acceptability of semiautomated methods for the measurement of mesothelioma tumor thickness in computed tomography (CT) scans.

MATERIALS AND METHODS

A computer interface was developed to allow the acquisition of semiautomated mesothelioma tumor thickness measurements, which require the manual selection of a point along the outer margin of the tumor in a CT section. After application of an automated lung segmentation method, the computer automatically identifies a corresponding point along the inner margin of the tumor (as represented by the lung boundary), constructs a line segment between the manually selected outer tumor margin point and the computer-determined inner tumor margin point, and computes tumor thickness as the length of this line segment. Three radiologists and oncologists independently reviewed line segments representing the semiautomated measurements generated by three different algorithms at 134 measurement sites in the CT scans of 22 mesothelioma patients. The observers either accepted a measurement line segment or modified it through the interface. Differences between the initial semiautomated measurements and the measurements as modified by the observers were analyzed.

RESULTS

The frequency with which observers accepted the semiautomated measurements without modification was as high as 86%. Of all measurements across all observers and methods (1,206 measurements), 89% were changed by 2 mm or less.

CONCLUSION

We have developed semiautomated methods to measure mesothelioma tumor thickness. The potential of these methods has been demonstrated through an observer study. We expect these methods to become important tools for the efficient quantification of tumor extent.

Pathology of mesothelioma

In this article, progress in distinguishing mesothelioma from mesothelial hyperplasia and fibrosing pleuritis was discussed. Advances in the immunohistochemical characterization of mesothelioma, in the recognition of entities that mimic mesothelioma, and in their distinction from mesothelioma were reviewed. Cytogenetic and molecular genetic contributions to the diagnosis of pleural synovial sarcoma were briefly summarized. The diagnosis of epithelial type mesothelioma can be established in most cases. Several mesotheliomas, however, especially rare subtypes, and sarcomatoid, desmoplastic, and poorly differentiated mesotheliomas continue to present diagnostic challenges.

Staging and response to therapy of malignant pleural mesothelioma

Earlier staging systems tended to concentrate on advanced malignant pleural mesothelioma (MPM) and considerable variation arose among the different systems. This was addressed in 1997 when the International Mesothelioma Interest Group (IMIG) staging system was approved. This is not a perfect system as many of the distinctions it makes cannot be identified by current computed tomography (CT) and magnetic resonance imaging (MRI) scanning. However presurgical staging using CT and MRI can be useful in delineating the extent and volume of disease and in detecting unexpected advanced disease as well as alerting clinicians to the possibility of early stage malignant pleural mesothelioma. Patients response to therapy can be measured using the response evaluation criteria in solid tumors (RECIST) criteria involving multiple measurements of a single diameter of tumour thickness.

Modified RECIST criteria for assessment of response in malignant pleural mesothelioma

BACKGROUND

The growth pattern of malignant pleural mesothelioma makes the use of RECIST (response evaluation criteria in solid tumours) response criteria difficult. We have developed and validated Modified RECIST criteria adapted to the growth pattern of malignant pleural mesothelioma.

PATIENTS AND METHODS

We evaluated 73 patients from two clinical trials of cisplatin/gemcitabine chemotherapy in malignant pleural mesothelioma. Tumour thickness perpendicular to the chest wall or mediastinum was measured in two positions at three separate levels on thoracic CT scans. The sum of the six measurements defined a pleural unidimensional measure. Bidimensionally measureable lesions were measured unidimensionally as for RECIST. All measurements were added to obtain the total tumour measurement. A reduction of at least 30% on two occasions 4 weeks apart defined a partial response; an increase of 20% over the nadir measurement, progressive disease. The validity of the modified criteria was gauged by evaluating survival and pulmonary function.

RESULTS

Response according to these criteria predicted for superior survival (15.1 versus 8.9 months; P = 0.03) and forced vital capacity (FVC) increase during treatment (P <0.0001). A significant correlation between change in linear tumour measurement and FVC was seen (R = 0.63; P = 0.0001).

CONCLUSION

These Modified RECIST criteria for tumour response correlate with survival and lung function and can be used to measure outcome in pleural mesothelioma.

Diffuse malignant mesothelioma of the peritoneum and pleura, analysis of markers

Diffuse malignant mesothelioma of the peritoneum is a rare diagnosis. Despite many histopathologic similarities between peritoneal and pleural tumors, clinical and prognostic features may be quite different. There is a paucity of data evaluating molecular features of peritoneal mesotheliomas. Therefore, we compared the results of a battery of immunohistochemical markers, some with therapeutic implications, in patients with primary peritoneal or pleural mesotheliomas. We examined 24 peritoneal and nine pleural malignant mesotheliomas with a battery of immunohistochemical markers (cytokeratin AE1/3, calretinin, c-kit/CD117, desmin, epidermal growth factor receptor (EGFR), estrogen receptors (ER), progesterone receptors (PR), MIB-1, and cleaved caspase-3) in an attempt to distinguish any differences in this tumor arising in these two distinct locations. The results indicate that the only marker to show a significant difference in its staining pattern between these two sites was EGFR (P=0.0004). In all, 92% (22/24) of peritoneal tumors demonstrated 3+ or 4+ immunoreactivity with EGFR, opposed to only 33% (3/9) pleural tumors. There was no significant difference in immunoreactivity between the pleural and peritoneal tumors with c-kit, ER, PR, cleaved caspase 3, calretinin, and desmin. There was a trend toward increased cytokeratin (P=0.07) and MIB-1 (P=0.08) expression in the peritoneal group. There was no significant difference in age, sex, or histologic subtype between the two locations. In conclusion, despite similarities between peritoneal and pleural mesothelioma, there are differences between this neoplasm arising in these two sites. The EGFR expression is more pronounced in peritoneal tumors compared to pleural tumors. The increased expression of EGFR in the peritoneal lesions may be of clinical significance with the recent emergence of epidermal growth factor receptor-targeted therapies.

Mortality from pleural mesothelioma in Rio de Janeiro, Brazil, 1979-2000: estimation from death certificates, hospital records, and histopathologic assessments

To obtain information about the occurrence of pleural mesothelioma on a population basis in Brazil, mortality related to pleural tumors in the State of Rio de Janeiro during 1979-2000 was examined. Death certificates with pleural tumors as the main cause of death and hospital records were analyzed, together with histopathologic material, which was reevaluated. Of 217 death certificates coded as pleural tumors, 34.1% were considered wrongly coded. Results after reclassification were: definite mesothelioma = 45 cases; probable = 7; possible = 31; inconclusive = 65; other tumors = 11. Thus, the number of mesotheliomas in Rio de Janeiro in 1979-2000 is estimated to have been 83. The analysis also suggests a problem with mortality codification in the State.

Unusual intraparenchymal growth patterns of malignant pleural mesothelioma

AIMS

Malignant pleural mesothelioma is known to mimic morphologically a number of diverse reactive and neoplastic conditions. We describe three unusual intraparenchymal growth patterns of malignant mesothelioma seen in a series of 200 malignant pleural mesotheliomas. The diagnostic pitfalls associated with these findings are described and their potential medico-legal implications are highlighted.

METHODS AND RESULTS

The study group comprised 200 malignant pleural mesotheliomas. In each case diagnosis was morphologically confirmed with ancillary immunohistochemistry using a broad panel of both mesothelial and epithelial markers. The patterns of intraparenchymal growth were documented and grouped as: direct subpleural; lymphangitic; and other. The 200 malignant pleural mesotheliomas comprised 118 epithelioid, 57 biphasic and 25 sarcomatoid, subtyped according to the WHO classification. Direct subpleural invasion was seen in 42 cases, lymphangitic spread in 27 cases. Other less well-defined intraparenchymal patterns included three sarcomatoid subtype malignant mesotheliomas exhibiting an intra-alveolar growth pattern mimicking epithelioid haemangioendothelioma. One epithelioid subtype malignant mesothelioma contained an intraparenchymal tumour nodule microscopically comprising lepidic spread of neoplastic cells over maintained alveolar structures mimicking bronchioloalveolar carcinoma. One epithelioid subtype malignant mesothelioma morphologically had areas in which alveoli were distended by discohesive epithelioid neoplastic cells with no interstitial invasion. The appearances mimicked desquamative interstitial pneumonia. Immunohistochemistry played an important role in the definitive diagnosis of each unusual parenchymal tumour deposit. In 126 malignant mesotheliomas no invasion of the subjacent lung parenchyma was identified.

CONCLUSIONS

An awareness of the unusual parenchymal growth pattern in malignant mesothelioma is important to prevent misdiagnosis of other entities. In the medico-legal setting, the presence of epithelioid haemangioendothelioma or bronchioloalveolar carcinoma (in the absence of asbestosis) may be deemed to impact upon the patient's anticipated life expectancy and thereby would decrease the compensation settlement.

Pyothorax-associated lymphoma: a review of 106 cases

PURPOSE

Pyothorax-associated lymphoma (PAL) is a non-Hodgkin's lymphoma developing in the pleural cavity after a long-standing history of pyothorax. Full details of PAL are provided here.

PATIENTS AND METHODS

Clinical and pathologic findings were reviewed in 106 patients with PAL collected through a nationwide survey in Japan.

RESULTS

Age of the patients with PAL was 46 to 82 years (median, 64 years), with a male/female ratio of 12.3:1. All patients had a 20- to 64-year (median, 37-year) history of pyothorax resulting from artificial pneumothorax for treatment of pulmonary tuberculosis (80%) or tuberculous pleuritis (17%). The most common symptoms on admission were chest and/or back pain (57%) and fever (43%). Laboratory data showed that the serum neuron-specific enolase level was occasionally elevated (3.55 to 168.7 ng/mL; median, 18.65 ng/mL), suggesting a possible diagnosis of small-cell lung cancer. Histologically, PAL usually showed a diffuse proliferation of large cells of B-cell type (88%). In situ hybridization study showed that PAL in 70% of the patients was Epstein-Barr virus (EBV)-positive. PAL was responsive to chemotherapy, but the overall prognosis was poor, with a 5-year survival of 21.6%.

CONCLUSION

This study established the distinct nature of PAL as a disease entity. PAL is a non-Hodgkin's lymphoma of exclusively B-cell phenotype in the pleural cavity of patients with long-standing history of pyothorax, and is strongly associated with EBV infection. Development of PAL is closely related to antecedent chronic inflammatory condition; therefore, PAL should be defined as malignant lymphoma developing in chronic inflammation.

[Pleural mesotheliomas. Current knowledge]

Pleural mesotheliomas are rare primary tumors of the pleura. Three groups are classified under the term mesothelioma: 1) benign pleural mesothelioma for which complete surgical treatment is curative with a good prognosis; 2) localized malignant mesothelioma which is a fibrosarcoma, best treated by wide en-bloc resection; 3) diffuse malignant mesothelioma which is mainly of epithelial type. The prognosis is poor in spite of all therapeutic approaches using irradiation, chemotherapy and surgery, alone or in combination, and long-term survivals are uncommon. Two surgical approaches are currently available for patients with diffuse mesothelioma: radical extrapleural pneumonectomy and pleurectomy/decortication. Rigorous combinations of multimodality therapy are needed to improve local control and survival.

[New WHO-classification of lung and pleural tumors]

A new classification of the World Health Organization (WHO) of lung and pleural tumours will be published presently. Compared with the previous edition of 1981 the changed parts more accurately reflect the available therapeutic choices and the prognostic characteristics of the different tumour types. The classification is based on conventional light-microscopical typing. Additional techniques (from histochemistry, immune histochemistry, electron microscopy and molecular biology) have not yet decisive influence on tumour typing. The dichotomy between small-cell and large-cell carcinomas is too simplistic, as the group of large-cell carcinomas is heterogeneous, and further differentiation leads to identification of tumour types with distinct therapeutic options and prognostic characteristics. There are new criteria for the classification of neuroendocrine tumours, such as the mitotic index. It is recommended to use the newly revised classification for diagnostic purposes, epidemiology and biologic studies.

[Morphological aspects of verification of pleural neoplasms in one's life time]

Difficulties of diagnosis of pleural neoplasms in biopsies are discussed. The short history of serous tumors as entity, their classification, methodological approaches to their morphological diagnosis are outlined. It is concluded that the problem of neoplastic pleural diseases verification can be solved by clinical and morphological correlations. Histochemistry, immunomorphology, and electron microscopy should be combined with conventional morphologic methods used in biopsy investigations.

[Malignant mesothelioma. Diagnosis and treatment]

In over 90% of cases, mesothelioma initially presents as a banal pleural effusion, contributing no orientation to the diagnosis. The pleural fluid can even disappear after initial puncture. For early diagnosis, simple puncture, with or without biopsy, does not suffice. Thoracoscopy is 98% diagnostic. The course depends on the stage, the histological type and the general status. A new international TNM classification has been proposed to allow comparison of series and to choose a treatment appropriate to the stade: at stage I, intrapleural, local immuno-chemotherapy treatment gives good results; at stages II and III, surgery followed by radiation therapy are indicated; at stage IV, symptomatic treatment alone is justified.

A proposed new international TNM staging system for malignant pleural mesothelioma from the International Mesothelioma Interest Group

STUDY OBJECTIVE

investigation of the behavior and treatment of diffuse malignant pleural mesothelioma (MPM) is hindered by the lack of an accurate universally accepted staging system. To address this problem, the International Mesothelioma Interest Group (IMIG) has developed a new TNM based staging system.

METHODS

the staging system was developed at a consensus meeting of IMIG members involved in clinical research in MPM, including the originators of previously proposed staging systems. The new staging system is based on the analysis of emerging information about the impact of T and N status on survival.

RESULTS

in contrast to five previous staging systems, the T descriptors designated as T1, T2, T3 and T4, provide precise anatomic definitions of the local extent of the primary tumour. The N descriptors, designated as N0, N1, N2 and N3, are virtually identical to those used in the International Lung Cancer Staging System. The stage groupings recognize new data about the better prognosis of T1 and N0 tumours and classify those tumours into stages I and II. The adverse impact of nodal metastases on survival noted in some recent surgical series warrants placing node positive tumours in stage III. Locally advanced unresectable (T4) tumours and extrathoracic disease (N3 or M1) are classified as stage IV.

CONCLUSION

this proposed staging system reconciles and updates several earlier systems, and can provide the framework for analyzing the results of prospective clinical trials aimed at improving the currently dismal prognosis of MPM.

Aspects of histopathologic subtype as a prognostic factor in 85 pleural mesotheliomas

BACKGROUND

The prognosis of patients with pleural mesothelioma is more dependent on "pretreatment factors" than on the effect of therapeutic interventions. Histopathologic subtype is one of several important prognostic factors in pleural mesothelioma, and several studies indicate that the epithelial subtype of pleural mesotheliomas has a more favorable prognosis than the sarcomatoid. In this study, we retrospectively evaluated qualitative and quantitative aspects of the tissue specimens used for histopathologic diagnosis in 85 patients with pleural mesothelioma.

MATERIALS AND METHODS

The prognostic roles of two different histopathologic classification systems were evaluated in 85 consecutive cases of pleural mesotheliomas. Efficiency of different diagnostic procedures, influence of the size of the biopsy specimens on the histopathologic diagnosis, and immunohistochemical profiles for histopathologic subtypes of mesotheliomas were also evaluated.

RESULTS

Patients with pure epithelial mesotheliomas (n = 35), and especially those with the tubulopapillary subtype (n = 18) of epithelial mesotheliomas, survived significantly longer than those with a sarcomatoid component (n = 50). With larger biopsy specimens (surgical biopsy, autopsy), more tumors were classified as biphasic (36/78 vs 9/44, p < 0.005). The sarcomatoid mesotheliomas comprised about 20% of the tumors regardless of type of biopsy. Staining intensity for cytokeratin CAM 5.2 was equal in all types of mesotheliomas, while intensity with cytokeratin AE1/AE3 decreased from the epithelial to the sarcomatoid mesotheliomas. Staining with vimentin was most intense among the sarcomatoid mesotheliomas, while with epithelial membrane antigen it was most intense among the epithelial mesotheliomas.

CONCLUSIONS

The quality of the biopsy specimens has considerable impact on the possibility to arrive at a correct histopathologic diagnosis. Based on our results, we suggest tubulopapillary mesotheliomas be regarded as "low-grade mesotheliomas" and other types, including the epithelioid type of epithelial mesotheliomas, as "high-grade mesotheliomas." This should be taken into account when designing clinical trials.

Sarcomas and other malignancies of soft tissue, retroperitoneum, peritoneum, pleura, heart, mediastinum, and spleen

BACKGROUND

Malignant neoplasms of the structural tissues, consisting mostly of soft tissue sarcomas, are morphologically diverse and rarely treated for epidemiologic purposes as individual entities. Our understanding to date of the pattern of occurrence of sarcomas is based largely on reports of limited individual clinic experience or case-control studies, each driven by a single hypothesis, and there have been virtually no descriptions according to specific morphologic type.

METHODS

The accumulated coverage of the SEER populations offers an opportunity to correct this deficit. Each of the diagnoses has been reported and coded using a single set of rules and described in relation to the population at risk in terms of age, sex, race, calendar period, anatomic location, and outcome. In addition, each morphologic type has been compared with each of the others with respect to the pattern of occurrence and survival.

RESULTS

For most of the individual morphologic entities, the pattern of occurrence is specific and unlike other patterns. Differences according to anatomic site, age, sex, race, and period-specific survival were found. Partly because of changes in diagnostic criteria over the years, differences in secular trend, other than that for Kaposi's sarcoma, could not be verified. Although some types of sarcoma may have important genetic determinants, there is evidence of environmental causation in others; for some varieties both genetic and environmental factors may operate. There is no evidence of improvements in survival.

CONCLUSIONS

The most likely basis for the observed patterns are morphology-specific differences in etiology and growth phase. Each of the entities should be considered etiologically distinct and should be studied individually whenever possible.

Pleuropulmonary blastoma is THE pulmonary blastoma of childhood

Pulmonary blastoma was defined by Spencer and others as a neoplasm with histopathological features thought to be reminiscent of Wilms' tumor. Unlike the other embryonal-fetal neoplasms that typically occur in early childhood, the majority of pulmonary blastomas have been reported in adults. One explanation offered by Spencer for the delayed clinical presentation of pulmonary blastoma is the continued development of lung parenchyma well past the postnatal period. It has been proposed that the pulmonary blastoma is a variant of carcinosarcoma, which is seen almost exclusively in adults. The classic pulmonary blastoma is described as a neoplasm with a mixture of primitive tubular profiles, immature blastema, and a spindle cell stroma. More recently, some have included the well-differentiated adenocarcinoma of fetal type as a pure epithelial expression of pulmonary blastoma. By contrast, most cases of pulmonary blastoma in children have been described as having an exclusive mesenchymal composition, either embryonal rhabdomyosarcoma or a complex, mixed blastematous and sarcomatous neoplasm. Some pulmonary blastomas in children, particularly those with only embryonal rhabdomyosarcoma, have presented as a peripheral multicystic lesion that has been interpreted as a developmental cyst, either cystic adenomatoid malformation or bronchogenic cyst. Other tumors have been described as intrathoracic and anatomically separate from the lung, like some extralobar sequestrations. We have proposed the designation pleuropulmonary blastoma for these pulmonary or extrapulmonary neoplasms of childhood. We propose that this neoplasm is the rightful pulmonary blastoma rather than the pulmonary blastoma of Spencer, which has been the long-time pretender to the title.

Thoracoscopy in pleural malignant mesothelioma: a prospective study of 188 consecutive patients. Part 2: Prognosis and staging

BACKGROUND

Thoracoscopy appears to be essential in identifying tumors at the beginning of pleural disease.

METHODS

Between 1973 and 1990, diagnostic thoracoscopy was carried out in a prospective series of 188 patients with malignant pleural mesothelioma (MPM). Biopsy samples were obtained in all cases, and diagnosis was confirmed by the French panel of mesothelioma specialists. In all patients we noted the degree of involvement of the parietal, diaphragmatic, or visceral pleura, and classified patients according to the Butchart system: Stage I (66 patients), II (110 patients), III (4 patients), and IV (8 patients). To assess prognostic factors, a multivariate analysis of clinical and endoscopic findings was performed according to the Cox model.

RESULTS

The most favorable factors were absence of weight loss at the time of diagnosis, absence of involvement of the visceral pleura, Butchart Stage I, and epithelial histopathologic type. When Stage I patients were subdivided into two groups according to whether or not they displayed involvement of the visceral pleura, a significant difference in survival was noted (32.7 months versus 7 months, respectively; P < 0.001).

CONCLUSIONS

Based on these findings, we propose to divide Butchart or Mattson Stage I into two subgroups, i.e., Stage IA in which only the parietal or diaphragmatic pleura is involved and Stage IB in which the visceral pleura is invaded. In the International Union Against Cancer (UICC) classification, T1 should be used for tumors restricted to the parietal or diaphragmatic pleura and T2 for tumors with additional involvement of the visceral pleura.

The effect of inaccuracies in death certification and coding practices in the European Economic Community (EEC) on international cancer mortality statistics

An investigation into the effect of national death certification and coding practices on published mortality statistics in eight EEC countries is reported. Doctors in each country were asked to complete specimen death certificates for a bank of written case histories. Certificates from each country were coded by their own offices and then by a WHO reference centre. Within and between countries, discrepancies occurred both in the doctors' diagnoses and in the codes assigned to certificates. At an international level these differences had serious implications for the comparability of mortality data for cancers of the cervix and uterus, and for mesotheliomas.

Sarcomatous type of malignant mesothelioma

Thirteen malignant mesotheliomas of a sarcomatous type were studied by light microscopy and ten were studied by electron microscopy. The histologic patterns varied from tumor to tumor, often resembling other soft tissue sarcomas. Electron microscopic observation showed most of the tumors to be composed of primitive cells. Despite their mesenchymal character, many tumors contained foci of rudimentary epithelial differentiation. It is concluded that both histologic types of malignant mesothelioma, the epithelial as well as the sarcomatous, originate from the same precursor cell at various points of its differentiation and reflect the range of maturation from the mesenchymal reserve cell to the epithelial mesothelial cell.

[Pleural mesothelioma: 3 developmental forms]

In the medical literature, there have been fewer reports on benign pleural mesotheliomas than on their malignant counterparts. We have reviewed the clinical, radiological and pathological features of mesotheliomas seen at the Hôtel-Dieu in Montreal over the past ten years. This experience leads us to postulate that there are three types of mesothelioma. The malignant form is often typical. Pedunculated lesions most often prove to be asymptomatic and benign. However, we have identified an intermediate category where the definitive nature of the mesothelioma could only be established after long term follow-up of the biological behaviour of the tumor.

[Anatomo-clinical calssification of primary tumors of the pleura and possibility of their surgical treatment]

A distinction is drawn between first category includes peduncolates, giant seslocal and diffuse primary tumours of the pleura on anatomopathological grounds. The first category includes peduncolated, giant sessile, and "deceptive" forms; the latter those in which the lung is surrounded by a "pleural" and "serous" mantle. Treatment is discussed and the soundness of surgical management is stressed.