A lung biopsy is a medical procedure involving the removal of a small piece of lung tissue or cells for examination under a microscope. This procedure is necessary to establish a definitive diagnosis for various lung conditions, most commonly to investigate suspicious masses or nodules identified on imaging scans. The primary goal is to determine if the abnormal tissue is cancerous, benign, or the result of an inflammatory process.
The specific name given to the lung biopsy depends entirely on the method used to collect the tissue sample. Doctors select the technique based on the location and size of the abnormality, the patient’s overall health, and the amount of tissue required for diagnosis.
Needle-Based Biopsy Procedures
Needle-based procedures are the least invasive methods for obtaining a sample, known as percutaneous or transthoracic biopsies because the needle is inserted through the skin and chest wall. These techniques rely on real-time imaging guidance, such as Computed Tomography (CT) or ultrasound, to precisely navigate the needle to the target lesion. This visualization ensures the needle accurately enters the suspicious area.
Fine-Needle Aspiration (FNA)
Fine-Needle Aspiration (FNA) uses a very thin, hollow needle to draw out a small collection of cells and fluid. This method is effective for cytological analysis, studying the characteristics of individual cells to determine if they are malignant. FNA may sometimes yield an insufficient sample for a full diagnosis.
Core Needle Biopsy (CNB)
A Core Needle Biopsy (CNB) utilizes a slightly wider needle to extract a solid, cylindrical piece of tissue, often called a core. This larger sample provides a better representation of the tissue architecture, allowing the pathologist to examine how the cells are structured. The solid sample is more reliable for detailed subtyping of cancer and performing complex molecular tests. Both FNA and CNB carry the risk of pneumothorax, or collapsed lung.
Scope-Guided Biopsy Procedures
Scope-guided methods involve the use of a bronchoscope, a thin, flexible tube equipped with a light and camera, which is passed through the nose or mouth and into the lung’s airways.
Transbronchial Biopsy (TBB)
This approach is called a Transbronchial Biopsy (TBB) when instruments are passed through the scope to pinch off small samples of lung tissue from the inner airways. TBB is useful for sampling lesions located near the central part of the lung or for diagnosing diffuse lung diseases, such as sarcoidosis.
Endobronchial Ultrasound (EBUS-TBNA)
Endobronchial Ultrasound (EBUS) integrates an ultrasound probe at the tip of the bronchoscope. The ultrasound allows the physician to visualize structures like lymph nodes and masses that lie just outside the airway walls. EBUS-guided procedures use a needle passed through the scope to sample these external structures, known as EBUS-TBNA. EBUS-TBNA is highly effective for sampling mediastinal and hilar lymph nodes, which are frequently involved in the spread of lung cancer. Sampling these nodes without external puncture improves the accuracy of cancer staging. These procedures are often performed under moderate sedation and benefit patients with centrally located lesions adjacent to major airways.
Surgical Biopsy Methods
Surgical biopsy methods are reserved for situations where less invasive procedures were inconclusive or when a significantly larger piece of tissue is required. These operations are performed in an operating room under general anesthesia.
Video-Assisted Thoracoscopic Surgery (VATS)
The most common technique is Video-Assisted Thoracoscopic Surgery (VATS). VATS is a minimally invasive procedure where a camera and specialized instruments are inserted through several small incisions between the ribs. The camera, called a thoracoscope, allows the surgeon to visualize the lung surface and remove a substantial wedge of tissue. Because VATS avoids the need to spread the ribs, patients typically experience less post-operative pain and have a faster recovery compared to traditional open surgery.
Open Lung Biopsy (Thoracotomy)
The traditional Open Lung Biopsy, or thoracotomy, involves a larger incision made on the side of the chest, often requiring instruments to spread the ribs. This method grants the surgeon direct, unimpeded access to the lung and is usually necessary when the lesion is difficult to reach, the patient has extensive scarring, or if VATS is technically challenging. Both surgical methods provide the largest, most robust tissue samples, frequently required for the definitive diagnosis of complex conditions like interstitial lung fibrosis.
Analyzing the Tissue Sample
Once the tissue is collected, it is immediately sent to a pathologist, the physician specializing in disease diagnosis through tissue examination. The sample is typically processed, fixed in a preservative like formalin, and embedded in wax to create a solid block. Extremely thin slices are then cut from this block, placed on glass slides, and stained with special dyes.
The pathologist examines these stained slides under a microscope to analyze the cellular structure, looking for abnormal cell growth, inflammation, or infection. Specific stains, such as Immunohistochemistry (IHC), are often used to identify proteins on the cells, which helps confirm the exact subtype of lung cancer. This detailed subtyping is crucial because it directly influences treatment decisions, including the selection of targeted therapies.
The pathology report ultimately provides the diagnosis, detailing whether the tissue is benign or malignant and confirming the specific type of disease present. In cases of malignancy, the report may also include the results of molecular testing, which identifies specific genetic mutations within the cancer cells. This comprehensive analysis transforms the tissue sample into actionable information for the patient’s care team.