Diffuse Intrapulmonary Malignant Mesothelioma Masquerading as Interstitial Lung Disease: A Distinctive Variant of Mesothelioma

Diffuse intrapulmonary mesothelioma mimicking pulmonary lepidic adenocarcinoma: a rare case report and review of the literature

Mesothelioma, with various clinical manifestations, radiological features, and histomorphological types, can be divided into epithelioid, sarcomatoid, and biphasic types, according to their histomorphological characteristics. There is a rare growth pattern of pleural mesothelioma: diffuse intrapulmonary mesothelioma (DIM), with a distinctive pattern of predominantly intrapulmonary growth, has no or minimal pleural involvement, and simulates interstitial lung disease(ILD) clinically and radiologically. A 59-year-old man presented to the hospital with recurrent pleural effusions for 4 years and a history of asbestos exposure. Computed tomography (CT) showed bilateral pure ground-glass opacity lesions, and the tumor cells showed a lepidic growth pattern pathologically. Immunohistochemical staining was positive for CK, WT-1, calretinin, D2-40, CK5/6, and Claudin4, while TTF-1, CEA, EMA, CK7, CK20, and other epithelial markers were negative. BAP1 loss its expression, and MTAP was positive in cytoplasm. CDKN2A was negative tested by Fluorescence in situ hybridization (FISH). The final diagnosis was DIM. In conclusion, we should recognize this rare disease to avoid misdiagnosis and delayed treatment.

When the Diagnosis of Mesothelioma Challenges Textbooks and Guidelines

The diagnosis of malignant mesothelioma (MPM) does not pose difficulties when presenting with usual clinico-radiologic features and morphology. Pathology textbooks and national/international guidelines generally describe the findings of classic MPM, underlining common clinical presentation, the gold standard of sampling techniques, usual morphologic variants, immunohistochemical results of several positive and negative primary antibodies in the differential diagnosis, and the role of novel molecular markers. Nevertheless, MPM often does not follow the golden rules in routine practice, while the literature generally does not sufficiently emphasize unusual features of its manifestation. This gap may potentially create problems for patients in sustaining a difficult diagnosis of MPM in clinical practice and during legal disputes. Indeed, the guidelines accidentally tend to favor the job of lawyers and pathologists defending asbestos-producing industries against patients suffering from MPM characterized by uncommon features. The current review is aimed at underlining the wide spectrum of clinical and radiological presentation of MPM, the possibility to consistently use cytology for diagnostic intent, the aberrant immunohistochemical expression using so-called specific negative and positive primary antibodies, and finally proposing some alternative and more unbiased approaches to the diagnosis of MPM.

Pseudocarcinomatous Mesothelioma: A Hitherto Unreported Presentation closely simulating primary lung cancer

Malignant mesothelioma (MM) has a wide range of clinical, radiologic, and pathologic presentations, mimicking lung cancer or interstitial lung diseases when predominantly involving the lung parenchyma. The case herein refers to a 79-year-old man, active smoker without asbestos exposure, incidentally discovered to have a pulmonary nodule in the right upper lobe (1.5 cm). The lesion was misinterpreted as primary lung adenocarcinoma at the frozen section in light of the predominant lepidic growth pattern. Definitive examination confirmed neoplastic proliferation along alveolar structures. However, the unusual globous shape of tumor cells along the alveoli abruptly merging with normal pneumocytes prompted us to perform some immunostains that surprisingly revealed a mesothelial differentiation (positive staining with calretinin, cytokeratins (CK5/6), D2-40, and negativity with BRCA-associated protein 1 (BAP1), Thyroid Transcription Factor 1 [TTF-1], claudin-4, carcinoembryonic antigen [CEA], and napsin). MM represents the pathologic counterpart of so-called pseudomesotheliomatous carcinoma, since it appears as a localized pulmonary neoplastic nodule displaying a predominant lepidic growth pattern (pseudocarcinomatous mesothelioma). The challenging diagnostic features of this unique case and a review of similar cases in the literature are discussed.

Pathology of Malignant Pleural Mesothelioma

Despite multiple diagnostic toolkits, the diagnosis of diffuse malignant pleural mesothelioma relies primarily on proper histologic assessment. The definitive diagnosis of diffuse malignant pleural mesothelioma is based on the pathologic assessment of tumor tissue, which can be obtained from core biopsy sampling, pleurectomy, or other more extensive resections, such as extrapleural pneumonectomy. Given its rarity and overlapping microscopic features with other conditions, the histologic diagnosis of diffuse malignant pleural mesothelioma is challenging. This review discusses the pathologic features and the differential diagnosis of diffuse malignant pleural mesothelioma, including select diagnostic pitfalls.

Assessment and Management of Occupational Hypersensitivity Pneumonitis

The diagnosis and treatment of occupational hypersensitivity pneumonitis (OHP) remain complex and challenging in the absence of diagnostic gold standards or clinical guidelines. This review provides an update of the recent literature regarding the different presentations of OHP and the diagnostic yield and value of the diagnostic tests currently available, which include occupational and medical history, laboratory tests (serum-specific immunoglobulins, environmental sampling), imaging, bronchoalveolar lavage, transbronchial biopsy, transbronchial cryobiopsy, surgical lung biopsy, and specific inhalation challenges. These tools provide a precise differential diagnosis within the framework of interstitial lung diseases. However, among the chronic fibrotic forms, distinguishing OHP from sarcoidosis, nonspecific interstitial pneumonia and idiopathic pulmonary fibrosis remains a diagnostic challenge. Avoidance of exposure is pivotal for OHP management, whereas corticosteroids are fundamental in the pharmacological approach to this disease. In addition, studies describing the long-term benefits of immunosuppressive and antifibrotic agents have increased the use of these treatments in OHP.

An unusual case of chylothorax

Pleural effusions occur in up to 70% of cases of malignant pleural mesothelioma (MPM). However, MPM rarely presents as a chylous effusion making it a diagnostic challenge. There are only six reported cases to date. Most cases of chylothoraces due to malignancy are due to lymphoma or bronchogenic carcinoma. We report an interesting case of MPM in a 75-year-old man who presented with recurrent chylothorax. He reported a four-month history of dyspnea and chest discomfort. Chest x-ray revealed a pleural effusion. Pleural fluid analysis was consistent with a chylothorax. Pleural fluid cytology was negative for malignancy. Computed tomography of the chest showed pleural calcifications, mediastinal adenopathy and left lung infiltrate. A fine needle aspirate of the lymph node and transbronchial biopsy specimen (TBBX) of the left lung infiltrate showed extensive reactive appearing mesothelial cells but none that appeared malignant. A video assisted thoracoscopic surgery was suggested but the patient declined. He returned 3 months later with recurrent pleural effusion and worsening airspace disease. Thoracentesis revealed a chylothorax again. Repeat analysis of TBBX and lymph node specimens showed extensive reactive appearing mesothelial cells. Due to concern for MPM, ancillary testing was obtained - loss of BRCA1 associated protein (BAP-1) and CDKN2A/p16 gene deletion. BAP1 staining was lost in the mesothelial cells supporting MPM. This case highlights a rare cause of MPM presenting as a chylous effusion. In a patient with an unknown etiology of chylothorax, MPM must remain in the differential.

The pathological and molecular diagnosis of malignant pleural mesothelioma: a literature review

Malignant pleural mesothelioma (MPM), an asbestos-induced tumor, represents significant diagnostic challenges for pathologists. Its histological diagnosis is stepwise and should be based on morphological assessment, supported by clinical and radiological findings, and supplemented with immunohistochemistry (IHC) and, more recently, molecular tests. The main diagnostic dilemmas are the differential diagnoses with benign mesothelial proliferations and other pleural malignant tumors. The present review is an update regarding the morphological, immunohistochemical, and molecular features with respect to MPM diagnosis. Data sources include a survey of the biomedical literature from PubMed (http://www.ncbi.nlm.nih.gov/pubmed) and textbooks focusing on the pathological diagnosis of MPM and associated immunohistochemical and molecular markers. The histological findings of MPM could facilitate its diagnosis and provide important prognostic information. The immunohistochemical approach should rest on the application of a panel including positive (mesothelial-related) and negative markers with greater than 80% sensitivity and specificity, which need to be selected based on morphology and clinical information. Moreover, in challenging cases, fluorescent in situ hybridization (FISH) testing for the p16 deletion and IHC to evaluate the loss of BRCA1-associated protein 1 (BAP1) expression could be useful in distinguishing benign from malignant pleural proliferations.

The Third Italian Consensus Conference for Malignant Pleural Mesothelioma: State of the art and recommendations

Malignant Pleural Mesothelioma (MPM) remains a relevant public health issue, and asbestos exposure is the most relevant risk factor. The incidence has considerably and constantly increased over the past two decades in the industrialized countries and is expected to peak in 2020-2025. In Italy, a standardized-rate incidence in 2011 among men was 3.5 and 1.25 per 100,000 in men and women, respectively, and wide differences are noted among different geographic areas. The disease remains challenging in terms of diagnosis, staging and treatment and an optimal strategy has not yet been clearly defined. The Third Italian Multidisciplinary Consensus Conference on Malignant Pleural Mesothelioma was held in Bari (Italy) in January 30-31, 2015. This Consensus has provided updated recommendations on the MPM management for health institutions, clinicians and patients.

The role of computed tomography in assessing pleural malignancy prior to thoracoscopy

PURPOSE OF REVIEW

Computed tomography (CT) scanning is part of the routine diagnostic work up of patients with suspected pleural malignancy but has a wide variation in the reported sensitivity and specificity. This review was to appraise the recent literature on the utility of CT scanning.

RECENT FINDINGS

When investigating patients for suspected pleural malignancy, the sensitivity of a malignant CT report may be higher than previously reported (68%), but the specificity seems significantly lower (78%). The predictive value of CT scanning (on all patients with pleural effusions) may be increased using a CT scoring system. Recent meta-analyses of the utility of PET give differing opinions on the value of this imaging modality. Further work needs to be done to define its place in the diagnostic pathway.

SUMMARY

CT scoring systems may allow further risk stratification. However, a low negative predictive value of a 'negative' CT scan could lead to false reassurance and missed malignancy. PET/CT does not currently appear to add additional diagnostic value. Pulmonary emboli should be considered in all patients being investigated for clinically suspected malignant pleural disease. Respiratory physicians should be mindful of rare or unusual presentations.

Epithelioid pleural mesothelioma concurrently associated with miliary pulmonary metastases and minimal change nephrotic syndrome - A hitherto undescribed case

Malignant pleural mesothelioma (MPM) is the aggressive disease typically spreading along the pleural surface and encasing the lung, leading to respiratory failure or cachexia. Rare cases with atypical clinical manifestation or presentation have been reported in MPM. We experienced a unique case of MPM concurrently associated with miliary pulmonary metastases and nephrotic syndrome. A 73-year-old Japanese man with past history of asbestos exposure was referred to our hospital for the investigation of the left pleural effusion. Chest computed tomography showed thickening of the left parietal pleura. Biopsy specimen of the pleura showed proliferating epithelioid tumor cells, leading to the pathological diagnosis of epithelioid MPM with the aid of immunohistochemistry. After the diagnosis of MPM, chemotherapy was performed without effect. Soon after the clinical diagnosis of progressive disease with skull metastasis, edema and weight gain appeared. Laboratory data met the criteria of nephrotic syndrome, and renal biopsy with electron microscopic examination revealed the minimal change disease. Steroid therapy was started but showed no effect. Around the same time of onset of nephrotic syndrome, multiple miliary lung nodules appeared on chest CT. Transbronchial biopsy specimen of the nodules showed the metastatic MPM in the lung. The patient died because of the worsening of the general condition. To our knowledge, this is the first case of MPM concurrently associated with multiple miliary pulmonary metastases and nephrotic syndrome.

Global mesothelioma epidemic: Trend and features

Background:

Mesothelioma incidence has taken epidemic proportions in various countries. The trend of the epidemic remains undefined.

Objective:

To collect the most recent available data on mesothelioma incidence in order to determine the present trend of the epidemic.

Materials and Methods:

Data of the Cancer and Mesothelioma Registries have been reviewed. In addition, numerous researchers were contacted to obtain supplementary information.

Results:

The highest incidence rates are reported from some countries in Europe (United Kingdom, The Netherlands, Malta, Belgium), and in Oceania (Australia, New Zealand). Relatively low incidence/mortality rates are reported from Japan and from Central Europe. In many countries a trend to increase continues to be observed. Data are not available for the mostly populous countries.

Conclusion:

Mesothelioma epidemic does not show signs of attenuation. The lack of data for a large majority of the world does not allow that the consciousness of the risks related to asbestos exposure is reached.

FISH analysis of intrapulmonary malignant mesothelioma without a clinically detectable primary pleural lesion: an autopsy case

Patients with malignant mesothelioma typically present with a pleural effusion or pleural thickening and masses. A rare autopsy case of mesothelioma presenting with multiple bilateral lung nodules without clinically detectable pleural lesions is presented. A definitive diagnosis of the video-assisted thoracic surgery specimen could not be made, though a pattern of fibrosis mimicking organizing pneumonia was identified. Despite corticosteroid therapy, follow-up chest computed tomography showed enlargement of multiple nodules accompanied by the appearance of pleural thickening and effusions. The patient died of respiratory failure 11 months after initial presentation. Autopsy and retrospective analysis of the video-assisted thoracic surgery specimen using a p16 fluorescence in situ hybridization assay showed p16 homozygous deletion. The final diagnosis was sarcomatoid mesothelioma, and the lung nodules were intrapulmonary metastases from a clinically undetectable pleural sarcomatoid mesothelioma. It is important both to consider the possibility of mesothelioma with unusual clinical, radiological and pathological presentations and to remember that p16 fluorescence in situ hybridization analysis can play an important role in the diagnosis of mesothelioma.