A hilar mass is an abnormal growth in the lung’s hilum, a region near the center of each lung that serves as a crucial gateway for major blood vessels and airways. While concerning, a hilar mass is not always indicative of cancer. Both non-cancerous and cancerous conditions can cause a mass in this area.
Understanding Hilar Masses
The hilum is a wedge-shaped area on the medial, or middle, aspect of each lung. It is the specific point where the main bronchus, pulmonary arteries, pulmonary veins, and nerves connect to the lung tissue. This entire collection of structures, along with associated lymph nodes, forms what is known as the lung root.
Enlargement of the hilum can occur due to tumors, elevated pressure in the pulmonary arteries, or enlarged lymph nodes. Such a growth might obstruct airways, compress blood vessels, or irritate nerves, potentially leading to various symptoms. Hilar masses are often detected incidentally during imaging studies performed for other reasons.
Common Non-Malignant Causes
Non-cancerous conditions frequently cause hilar masses, often due to enlarged lymph nodes. Infections are a common reason for lymph node swelling, including bacterial infections like tuberculosis, which can mimic lung malignancy. Fungal infections, such as histoplasmosis and coccidioidomycosis, especially in endemic areas, also lead to enlarged hilar lymph nodes.
Inflammatory conditions, like sarcoidosis, are another frequent cause. Sarcoidosis, characterized by granuloma growth, often presents with bilateral hilar lymph node enlargement. Though less common, it can also appear as a solitary mass, making differentiation from cancer challenging. Benign tumors, such as hamartomas, are also non-malignant causes. These common benign lung tumors are composed of disorganized normal lung tissues. While usually found in the peripheral lung, hamartomas can occur in the hilar region and are often discovered incidentally.
Malignant Causes
Hilar masses can also arise from various cancerous conditions. Primary lung cancers commonly manifest as masses in the hilar region, including types like squamous cell carcinoma, small cell lung cancer, and adenocarcinoma, which originate within the lung itself. These cancers often involve the main bronchus or surrounding hilar lymph nodes.
Beyond primary lung cancers, metastatic cancers that have spread from other parts of the body can also appear as hilar masses. Cancer cells can travel through the lymphatic system and cause enlargement of the hilar lymph nodes. Common primary cancers that may metastasize to the hilar lymph nodes include breast cancer, colon cancer, kidney cancer, and lymphomas. When cancer is the cause, the mass usually requires prompt diagnosis and treatment due to its potential for rapid progression.
Diagnostic Approach
Determining the nature of a hilar mass typically involves a structured diagnostic approach, beginning with imaging studies. A chest X-ray is often the initial step, though a more detailed view is usually needed due to the overlap of structures in the hilum. Computed tomography (CT) scans provide detailed cross-sectional images, helping to visualize the size, location, and characteristics of the mass more clearly. A positron emission tomography (PET) scan may also be used to assess metabolic activity, which can help differentiate between cancerous and non-cancerous growths.
Following imaging, a definitive diagnosis often requires obtaining tissue samples. Bronchoscopy, where a thin, flexible tube is inserted into the airways, allows direct visualization and biopsy of central lesions. Endobronchial ultrasound (EBUS) is often performed during bronchoscopy to guide fine-needle aspiration of lymph nodes or masses. For inaccessible masses, a CT-guided biopsy, where a needle is inserted under CT guidance, can obtain tissue. In some instances, a surgical biopsy may be necessary for a sufficient sample. Patient medical history and a physical examination also provide important context.