Pleural diseases involve the parietal and visceral pleura and may be of either inflammatory or malignant origin, often resulting in pleural effusions. The diagnostic evaluation of pleural effusions includes chemical and microbiological studies, as well as cytological analysis, which can provide further information about the etiological disease process. However, 40% of pleural effusions remain undiagnosed after an initial thoracocentesis. [1, 2]
Pleural biopsy is recommended for evaluation and exclusion of infectious etiologies such as tuberculosis or malignant disease, particularly malignant mesothelioma.  Connective tissue disorders such as rheumatoid disease can also present with pleural involvement, requiring pleural biopsy for diagnosis. In addition, pleural thickening in the absence of pleural effusion may require further histological evaluation. It is important to understand that the etiology of pleural effusion remains unclear in nearly 20% of cases. 
Various biopsy techniques are available to diagnose pleural disease. These range from older techniques, such as blind or closed pleural biopsy, to newer techniques including image-guided and thoracoscopic biopsy. The latter techniques have higher diagnostic yield and provide better diagnostic sensitivity. In addition, the use of immunohistochemistry provides increased diagnostic accuracy. 
Indications for pleural biopsy include the following:
Recurrent pleural effusion of unknown etiology
Pleural mass or thickening
Closed Needle Pleural Biopsy
Cope needles and Abrams needles, as shown in the images below, are most commonly used for blind or closed needle biopsy. This procedure is generally performed in the setting of a large pleural effusion without any imaging other than chest radiography.
The patient is positioned and the biopsy site is selected after careful physical examination and review of imaging. Under aseptic measures, lidocaine is injected locally to anesthetize the selected site. A small skin nick is made with a scalpel blade.
The Cope needle with stylet is introduced through the skin incision at the upper surface of the rib in order to prevent neurovascular bundle damage. The needle is advanced until pleural fluid is obtained. The stylet is then removed and the biopsy trocar introduced. A 50-mL syringe is attached with a biopsy needle, which provides a closed system through which pleural fluid may be withdrawn, confirming the location of the biopsy needle in the pleural space. The biopsy needle is turned, with the right-angled projection facing downward. Both the outer cannula and the biopsy trocar are partially withdrawn until the parietal pleura is engaged. Gentle traction is applied to the biopsy trocar with one hand, and the outer cannula is advanced with a rotary motion. This action allows dissection of pleural tissue and intercostal muscle.
The biopsy needle is removed, during which the patient is instructed to make an “EEEEE” sound to minimize the risk of air entry. The biopsy specimen is collected with the attached syringe applying positive pressure. The needle site is observed for bleeding complications, and a pressure dressing is applied to prevent subcutaneous accumulation of pleural fluid.
The Abrams pleural biopsy needle consists of 3 parts, with 2 concentric tubes and a stylet. The outer tube has a trocar point and a deep notch behind the trocar point that can be closed with inner tube rotary movement, allowing cutting of the pleural tissue. The general technique for pleural biopsy with the Abrams needle is similar to that described for the Cope needle.
Blind pleural biopsy is also performed using a Tru-cut needle in the setting of moderate to large pleural effusions, with results that are comparable with those obtained with Abrams and Cope pleural biopsy needles. [5, 6] However, the Tru-cut needle is generally used with image guidance via ultrasonography or CT scanning.
Complications and precautions
Injury to adjacent organs during pleural biopsy, including liver, kidney, and spleen, is rare. Chest radiography is recommended to exclude immediate postprocedure complications, including pneumothorax. The incidence of pneumothorax with closed needle biopsy is approximately 8%-18%. 
Hemorrhagic states are considered a relative contraindication to pleural biopsy. The coagulation profile should be corrected prior to any biopsy procedure to minimize the risk of bleeding, including chest wall hematoma and hemothorax.
Needle biopsy of the pleura is useful for establishing the diagnosis of malignant or tuberculous pleural effusion. Multiple pleural biopsies are taken to increase the diagnostic yield. Pleural biopsy in combination with pleural fluid cytology improves the yield.  Needle biopsy of parietal pleural is more valuable in patients with suspected tuberculous effusion than in those with malignant effusion. The initial biopsy may demonstrate granuloma in 50%-80% of patients. 
In a recent study by Pandit et al using the Abrams needle, pleural biopsy tissue yielded the diagnosis of tuberculosis and malignancy in 90.9% and 63.2% of cases, respectively, and tubercular granuloma were present histopathologically in all cases of tuberculosis. The analysis of the pleural fluid for acid-fast bacilli stain was negative in all cases of confirmed tuberculous effusion, with a pleural tissue acid fast stain positive in only 22% of cases.  Granulomatous pleuritis is not specific for tuberculosis; it is also found in other disease processes, including fungal infections, sarcoidosis, and rheumatoid disease.
In a large retrospective analysis of 414 patients, needle biopsy of the pleura was determined to be nonspecific, except in patients with tuberculous pleurisy. 
Multiple studies have compared the diagnostic sensitivity of the Cope needle with that of the Abrams needle.  In a 2006 study of 57 patients with pleural tuberculosis, the diagnostic yield for the Cope needle was 85% compared to 57% for the Abrams needle. However, this finding did not reach statistical significance. The incidence of pneumothorax was higher with the Cope needle than with the Abrams needle.  In addition, the Cope needle requires more patient cooperation to exhale maximally in order to create less negative intrapleural pressure and thus minimize the risk of pneumothorax.
One study utilized a cytological brush to increase the yield of the closed pleural biopsy procedure with the Cope needle. This technique was superior (91% yield) to that achieved either with pleural fluid cytology (67% yield) or pleural biopsy (58% yield) in malignant pleural effusions. 
In a 2010 study by James et al, 48 patients with pleural effusion underwent closed pleural biopsy with a Tru-cut biopsy needle. The diagnostic yield of closed pleural biopsy was 62.2% in cases of all exudative pleural effusion, 76.2% in cases of tuberculous pleural effusion, and 85.7% in cases of malignant pleural effusion. 
Given the inability to target the abnormal thickened pleura and the frequent complications (eg, pneumothorax) associated with a closed pleural biopsy,  this procedure is restricted to patients with a large pleural effusion and has largely been replaced with image-guided pleural biopsy.
Image-Guided Pleural Biopsy
The procedural yield of pleural biopsy using ultrasonography or CT guidance is increased owing to the ability to precisely target an abnormal area of the pleura.  Ultrasonography is more sensitive in detecting loculated pleural effusions. It also has the advantage of providing a real-time approach to the biopsy without radiation. CT guidance allows better visualization of the extent of focal pleural masses, in addition to a clearer delineation of parenchymal pathology.
An area of pleural abnormality is identified using ultrasonography or CT imaging. The patient is then positioned according to the pleural lesions to be biopsied—prone for paravertebral lesions and supine for lateral or anterior lesions. Automated cutting needle devices, as shown in the images below, provide better histological samples than fine-needle aspiration. Three or more samples are generally obtained to ensure adequate pleural tissue for histopathological diagnosis.
Utilizing a sterile technique, a local anesthetic agent is administered. The large coaxial needle with stylet is then advanced under ultrasound or CT guidance into the pleural lesion, as depicted in the images below.
The stylet is then removed manually, and the cutting needle device is placed with a tip proximal to the biopsy site to allow the “throw” of device. The tissue is obtained with the activation of the biopsy device (see image below). Multiple pleural biopsies can be collected while keeping the coaxial outer needle in place.
Diagnostic advantages and limitations
Image-guided pleural biopsy is safe and allows for the ability to biopsy abnormal pleural tissue. The cutting biopsy needle appears to be more sensitive for malignancy than fine-needle aspiration, with a sensitivity of 91% in the diagnosis of mesothelioma.  The complication rates are lower for image-guided biopsy than for blind pleural biopsy, particularly in relation to pneumothorax.  Patients who are unable to hold their breath during the biopsy, either because of underlying lung pathology or positive pressure ventilation, are more likely to develop the complications of pneumothorax and lung injury.
The advancement of endoscopic instrumentation has allowed for the ability to directly visualize the pleural space in a less-invasive fashion. This minimally invasive procedure is known as pleuroscopy and is performed by a pulmonologist in the endoscopy suite or in the operating room under conscious sedation with local anesthesia. The endoscope is introduced into the pleural cavity by making a window between the ribs. This allows direct visualization of pleural pathology, biopsies, and chest tube placement with pleurodesis for recurrent pleural effusions.
The semirigid pleuroscope used for the procedure is similar to a bronchoscope in design and handling. The difference is that the pleuroscope shaft has two sections—the larger proximal rigid portion and flexible distal end, which moves with the handle. The pleuroscope has a working channel to accommodate the biopsy forceps and other instruments. A disposable plastic trocar allows passage of the scope through the chest wall.
Pleuroscopy is performed with a semirigid bronchoscope that functions similarly to a flexible bronchoscope. Continuous cardiopulmonary monitoring with electrocardiography and pulse oximetry is conducted.
An intravenous narcotic (fentanyl) and benzodiazepine (midazolam) are used for conscious sedation. Alternatively, general anesthesia with intubation can also be considered.
The patient is placed in the lateral decubitus position, with the affected side facing upward.
The procedure can be initiated through an intercostal incision, or a pneumothorax can be introduced prior to the procedure, with drainage of the pleural fluid. The pneumothorax allows the lung to collapse and move away from the chest wall to facilitate trocar insertion. The site of trocar insertion depends on the suspected pathology. If malignancy is suspected, the trocar is advanced over the sixth intercostal space at the midaxillary line.  Otherwise, the fourth space is preferred, given the better visualization of the lung apex from this position. For diagnostic purposes, a single-puncture technique is used that involves a 1- to 2-cm incision in the midaxillary line between the fourth and seventh intercostal spaces of the chest wall.
Multiple parietal pleural biopsies can be obtained through the single port of entry with the flexible biopsy forceps. A double-puncture technique is preferred for adhesiolysis, lung biopsy, and complex loculated fluid drainage. A small-bore catheter or chest tube is placed at the conclusion of the procedure and can be removed after the lungs are fully inflated.
Pleural biopsy samples obtained with the semirigid pleuroscope are small, given the size of the flexible biopsy forceps. Obtaining deeper parietal pleural specimens may be limited since the biopsy forceps lack mechanical strength. Obtaining multiple (5–10) pleural biopsies from abnormal areas and taking several samples from the same location repeatedly ensures adequate biopsy depth. 
The flexible-rigid pleuroscope is considered to be a safe procedure, with no morbidity or mortality observed in a study of 51 patients.  The major concern of the procedure is pleural hemorrhage from underlying intercostal blood vessels.
Immediate pressure using forceps and a small piece of gauze can be applied to control bleeding. If bleeding is significant, an additional incision should be considered to access the pleural cavity in order to perform tissue cauterization. If bleeding is not controlled with direct pressure and cauterization, ligation of the bleeding vessels with endoclips should be considered. Ongoing bleeding may require thoracotomy.
Other common complications include prolonged air leak, subcutaneous emphysema, postprocedure wounds infections including empyema, and chest wall metastasis from mesothelioma. 
Video-Assisted Thoracic Surgery
Video-assisted thoracic surgery (VATS) allows additional access to lung tissue and operative interventions, including lung biopsies, lobectomy, pericardial window placement, and empyema drainage. VATS is carried out by surgeons in an operating room under general anesthesia using single-lung ventilation with double-lumen endotracheal intubation.
VATS is performed with rigid endoscopic equipment, including a light source, an endoscopic camera with a video monitor, and a recording system (see images below). 
The different telescopes have various angles, from 0° for direct visualization to oblique (30° or 50°) and periscopic (90°) viewing. Various sizes of trocars are deployed as a means of introduction for the rigid telescope through the chest wall.
VATS is performed after placing a double-lumen endotracheal tube or a single-lumen tube with a bronchial blocker. The patient is usually placed in the lateral decubitus position with the affected area exposed. However, the procedure can also be performed in the supine position.
Using sterile techniques, 1-3 incisions, each 0.5-1 cm, are placed. The initial port site is created by incising the skin with the scalpel, then using a hemostat to bluntly spread the fascia and muscle layers until the pleural cavity is entered. The first incision placement should be at the maximum distance from the site of dissection or inspection to allow better visualization. Surgical interventions are made over the rib to prevent any injury to the neurovascular bundle. One of the incisions is usually located at a site suitable for the placement of the chest tube at the conclusion of the procedure. The second incision is placed more cephalad in a more anterior or posterior position depending on area of interest to be biopsied.
A port is placed through the first incision and a camera is inserted. The second incision is created with direct visualization of the camera from the inside. The pleural space is then inspected and areas of interest are biopsied at multiple sites after a thorough inspection is completed. Biopsy samples can be collected with biopsy forceps or other endoscopic instruments. After completion of the biopsy, the camera is rotated between port sites to check for hemostasis. A chest tube is then placed. The lung is then reinflated, and the remaining port site is closed with absorbable sutures.
Chest tubes are removed when air leaks have resolved and drainage is at acceptable levels. Chest X- Ray is performed post procedure and after removal of the chest tube to assess for pneumothoax.
Several factors can limit this diagnostic intervention, including marked coagulopathy, an inability to obtain unilateral lung ventilation, or inability of the patient to tolerate the procedure because of hypoxemia. Adhesions represent a relative contraindication depending on their location and density.
The reported complications of VATS are similar to those seen with pleuroscopy, including mesothelioma tract metastasis. Mesothelioma has been reported to spread along the tracks of surgical biopsy incisions, chest tubes, and biopsy needles. The reported incidence of 22% for tract metastasis was higher with surgical biopsy compared to 4% with needle biopsy in one study of 100 patients.  Prophylactic radiation may be helpful, although this is controversial. [19, 20]
In patients with pleural lesions or pleural thickening, image-guided pleural biopsy should be the primary method of investigation. Thoracoscopy would be of clinical benefit in nontuberculous benign pleural effusions without pleural thickening.