Cytological diagnosis of malignant pleural mesothelioma

Malignant pleural disease

Malignant pleural disease represents a growing healthcare burden. Malignant pleural effusion affects approximately 1 million people globally per year, causes disabling breathlessness and indicates a shortened life expectancy. Timely diagnosis is imperative to relieve symptoms and optimise quality of life, and should give consideration to individual patient factors. This review aims to provide an overview of epidemiology, pathogenesis and suggested diagnostic pathways in malignant pleural disease, to outline management options for malignant pleural effusion and malignant pleural mesothelioma, highlighting the need for a holistic approach, and to discuss potential challenges including non-expandable lung and septated effusions.

Diagnostic utility of BAP1 for malignant pleural mesothelioma in pleural fluid specimens with atypical morphology

OBJECTIVE

To assess the utility of BRCA1-associated protein 1 (BAP1) immunohistochemistry (IHC) for the diagnosis of malignant pleural mesothelioma (MPM) in fluid samples with atypical cytology.

METHODS

Pleural fluid samples with an atypical mesothelial proliferation (diagnostic categories: 'atypical' and 'suspicious') received between January 2015 and March 2018 at a tertiary referral centre were identified. Results of routine IHC testing were recorded for each case. BAP1 by IHC was performed and a final diagnosis sought from subsequent pathology specimens, medical records, or consensus clinical diagnosis.

RESULTS

Of 50 cases identified, 41 were reported as atypical and 9 as suspicious. Seven (14%) demonstrated loss of BAP1 staining, 40 retained BAP1 staining, 1 had heterogeneous staining, and 2 had insufficient cells for analysis. All seven cases with BAP1 loss were diagnosed with MPM on follow-up. Of those with retained BAP1, 52.5% (21) were subsequently diagnosed with MPM, while 40% (16) had non-MPM diagnoses after a median follow-up of 24 months. Three cases were not further investigated based on patient and clinician decision. The case with heterogeneous staining was diagnosed as mesothelioma by clinical consensus.

CONCLUSIONS

BAP1 IHC loss is highly specific for malignancy and has value as a rule-in test. Even in a tertiary centre with clinical interest in the cytological diagnosis of MPM this investigation was able to increase diagnostic accuracy beyond routine IHC studies. Cytological criteria remain valuable, as retained BAP1 in an atypical or suspicious mesothelial proliferation cannot exclude malignancy.

A challenging diagnosis of malignant mesothelioma with osteosarcomatous differentiation metastasizing to bone

Malignant pleural mesothelioma (MPM) is an insidious primary neoplasm of the pleura that can be challenging to diagnose and is commonly considered to be only locally invasive. We present the case of a 74-year-old male who presented with clinical features of MPM but from whom pleural fluid and biopsies initially suggested benign pathology. He later developed diffuse bony metastases and re-examination of pleural biopsies using modern immunohistochemistry and molecular testing revealed a diagnosis of sarcomatoid and desmoplastic MPM with heterologous osteosarcomatous differentiation. This case not only demonstrates the rare potential of skeletal metastasis of MPM, but also highlights the importance of recognizing the utility of modern diagnostic tests and their potential to prevent the need for unnecessary invasive procedures. To our knowledge this is the first description of this rare histological sub-type presenting with skeletal metastases.

Surgical and non-surgical management of malignant pleural effusions

INTRODUCTION

Optimal management of malignant pleural effusion (MPE) is important in the care of patients with advanced cancer. Surgical (especially video-assisted thoracoscopic surgery (VATS)) and non-surgical strategies are available. Clinicians should be aware of the evidence supporting the use of different modalities to guide treatment choice. Areas covered: This review covers published evidence of the advantages and disadvantages of VATS and non-surgical alternatives for MPE management. Expert commentary: Randomized clinical trials (RCTs) are needed to define the roles and benefits of VATS as existing literature is often flawed by selection bias. Three RCTs have failed to show benefits of VATS talc poudrage over bedside talc pleurodesis. VATS-pleurectomy offered no survival advantage in a RCT of mesothelioma patients. Modification of VATS techniques has reduced the invasiveness and associated risks. Future trials should compare VATS with contemporary, non-surgical approaches (especially combined Indwelling Pleural Catheter (IPC) and chemical pleurodesis therapy). Individualized management for different subgroups of MPE patients should be a long-term research goal. Studies are needed on better patient selection, and adjunct non-invasive, supportive (e.g. nutrition and exercise) therapies.