Patients presenting with radiologically confirmed pleural disease including (but not limited to) pneumothorax, pleural effusion, pleural thickening or pleural cancer (mesothelioma) to North Bristol NHS Trust will be screened and invited to participate by a member of the study team. The team will collect data on the patient’s demographics, past medical history and history of current illness, smoking status including cannabis, asbestos and other inhalational exposures, clinical frailty score (CFS) and performance status (PS). The team will also collect data related to their condition and its management, for example, radiological and thoracic ultrasound appearances, the number and type of interventions undertaken and digital measurements of air leaks in the case of pneumothorax. For patients with pleural effusions, if blood or pleural fluid samples are collected as part of their routine care, additional research samples will also be collected for use in current or future studies. For patients who undergo a pleural biopsy procedure following enrolment, additional tissue samples may be obtained and retained for research purposes if felt appropriate by the operator. These data and sample collections are not study-specific procedures but are performed as part of the participants’ routine clinical care. At enrolment patients will be asked to complete 2 routine questionnaires to provide patient-reported outcome measures. These are study-specific, not part of the patient’s routine care. Where necessary, additional PROMS relevant to a specific sub-study the patient may be eligible for may also be collected during the baseline assessment. Further data will be collected from the patient’s medical records at 4 months and 12 months post enrolment, to encompass the patient’s length of stay, number and type of interventions, and mortality. These two timepoints allow for the collection of complete data sets, acknowledging that some patients may have a prolonged diagnostic pathway or require recurrent procedures to manage their symptoms. A final diagnosis will be recorded after 12 months, based on the diagnosis of their treating clinician, and ratified by a second pleural specialist.