Isolated lung nodules, must it be lung cancer?

What is an isolated pulmonary nodule?

Solitary Pulmonary Nodule (SPN) is a solitary lung lesion that is less than 3 cm in diameter. It is surrounded by lung tissue and is not associated with other abnormalities of the lung or nearby lymph nodes.

An isolated pulmonary nodule is usually asymptomatic. It is like a “sleeper” that grows quietly in the body and is often detected during a chest x-ray (usually only nodules >1 cm in diameter are detected by x-ray). In the United States, approximately 150,000 isolated pulmonary nodules are detected on chest radiographs or CT scans each year.

After an isolated pulmonary nodule is found, further evaluation is often needed. Most isolated lung nodules are benign, but they can also be early primary lung cancer, or cancer from another site that has metastasized to the lungs. Different departments have different diagnoses and different management, and it is important to know how to make an accurate diagnosis as it is easy to misdiagnose clinically.

Also, if lung cancer is diagnosed, the 5-year survival rate is 55% in the early stages and only 4% in the late stages, so early diagnosis and treatment is very important.

Is an isolated lung nodule always lung cancer?

No.

No. In fact, there are many possible causes of isolated lung nodules:

Tumors (both benign and malignant).
- Lung cancer
- Metastatic lung cancer (metastasis from other sites to the lungs)
- Lymphoma (tumor of lymphoid tissue)
- Carcinoid tumor (a small, slow-growing, metastatic tumor)
- Malignant tumor (an abnormal mass formed by misaligned growth in normal tissue)
- Fibroma (a fibrous connective tissue tumor)
- Neurofibroma (a noncancerous tumor of nerve fibers)
- Germ cell tumor (a tumor composed primarily of immature, undifferentiated cells)
- Sarcoma (a malignant tumor of connective tissue origin)

Infectious inflammation: sarcoidosis (small granulomatous inflammatory lesions)
- Bacterial infections: such as tuberculosis or nocardia (purulent granulomatous lesions of the lung produced by Nocardia)
- Fungal infections: histoplasmosis, coccidioidomycosis, budding mycosis, or cryptococcosis
- Lung abscess (septic necrotizing lesion of lung tissue)
- Spherical pneumonia (infection caused by a virus or bacteria; alveoli filled with fluid and cells)
- Encapsulosis (a type of cyst caused by the larvae of Echinococcus spp.)

Non-infectious inflammation.
- Rheumatoid arthritis (a connective tissue disease; the main symptom is joint pain)
- Wegener’s granulomatosis (a necrotizing inflammatory disease of small blood vessels)
- Nodular disease (a granulomatous lesion of unknown etiology, often involving multiple organs)
- Lipoid pneumonia

Congenital factors.
- Arteriovenous malformation
- Pulmonary isolation (a rare congenital developmental anomaly of the lung)
- Pulmonary cysts (cystic lesions containing gas, fluid, or semisolid material)

Other causes.
- Pulmonary infarction (death of part of the lung tissue due to a sudden lack of blood supply)
- Circular lung atelectasis (reduction or loss of air in part of the lung)
- Mucus embolism (the lung is filled with mucus)
- Progressive massive fibrosis of the lung, also known as pneumoconiosis, “black lung disease”