Single Pulmonary Nodule

 

Single Pulmonary Nodule.

         PKGhatak, MD

In certain circumstances, a Chest CT scan is obtained as a part of workup - like a seat belt injury in an automobile accident or an undetermined cause of chest pain or shortness of breath, and to the surprise of the patients and doctors, a single pulmonary nodule is detected on the CT scan.

The incidence of an unsuspected Single Pulmonary Nodule (SPN) is 1 million / year in the USA. The attending doctor must give the patient the most recent information about the possible cause of the SPN. In the USA there is a 40 % chance that the SPN is a growth at the initial time of detection. The vast majority of these are benign lesions, if the nodule is less than 3 cm then only about 1 % of all the nodules so detected turn out to be malignant. Whether the SPN is malignant or benign, that depends on many factors including the radiological features of the SPL.

The first question doctor asks the patient is whether he/she had a CT scan of the chest or chest x-ray previously, if so, that x-ray/CT scan must be reviewed and compared with the recent CT of the chest. Say, 2 years earlier CT, the SPN was of the same size - it was most likely a benign lesion.

This is important because no one wants to miss a diagnosis Ca of the lung in a very early stage because the cure rate is 90 % at that stage compared with 30 % in stage II CA lung.

How to define a Single Pulmonary Nodule.

This definition is radiological and strictly adhered to.

These are the features: a discrete, well-marginated, rounded opacity, not exceeding 3 cm in diameter, surrounded by normal lung tissue; away from the hilum and mediastinum of the lung and no sign of pleural effusion, atelectasis and lymph node enlargement.

Nodules over 3 cm are called pulmonary masses. It takes 10 years for a nodule to reach the first 1 cm size.

What are common causes of SPN.

The three most common categories of SPN are benign adenoma, granuloma, and malignant tumor. The percentage of these conditions varies according to counties and even different regions of the same country. For example, in the desert region of the USA granulomas from fungal infections are more frequent than tumors, in developing counties granuloma of Tuberculosis is more prevalent.

What are granulomas.

A granuloma is a localized collection of inflammatory cells surrounded by blood vessels.

Granulomas are of two kinds- Inflammatory and No-Inflammatory.

Infectious causes are Tuberculosis, Histoplasmosis, Coccidioidomycosis, Cryptococcus, Blastomycosis, Nocardiosis, and Hydatid cysts.

Non-infectious granulomas.

Rheumatoid nodules, Granulomatous angiomatosis, Sarcoidosis.

What are benign lung tumors.

Bronchial adenomas, hamartomas, benign tumors originate from cartilage, connective tissues, muscles, etc. And a special group of bronchial adenomas called Carcinoids.

What are the radiological signs of SPN being cancer,

SPN larger than 3 cm in diameter, irregular margin, ground-glass appearance (structure of lung is visible through the lesion), stipple calcification, eccentric calcification; doubling time is short (less than 120 to 600 days). Care must be taken not to call an opacity a nodule if it is located outside the lungs, artifacts, foreign bodies, and nipple shadow.

What are the risk factors for malignancy.

Chance of malignancy increases with 30 + years of smoking history, older age; exposure to radon, asbestos, Nickle, chromium, vinyl chloride, polycyclic hydrocarbon; history of previous malignancy and chest radiation.

Nodule size and a chance of malignancy.

 5 cm nodules have a 60 % chance of malignancy, nodules 8 cm are 80-90% malignant.

What lab tests are required to diagnose benign lesions.

Serology test for collagen vascular disease, Rh factor. Serology for fungal infections, and fungal antigen tests where possible. Angiotensin converting enzyme for sarcoidosis., p ANCA and cANCA for angiitis. For Pulmonary Tuberculosis - interferon gamma release assay.

Follow up CT scan when initial CT and other tests are inconclusive.

For less than 3 cm lesions yearly CT scan. If stable for 3 years, then no further scans.

For 3 to less than 5 cm lesions 3 to 6 months interval CT scans.

For 5 to 8 cm lesions an initial biopsy is called for.

How to proceed with SPL.

If history, radiological scans including PET scans, and various blood tests are inconclusive then a Biopsy of the SPL is called for.

To improve the chance of a better yield by biopsy and with minimum damage of normal lungs, these important additions have taken place.

Skinny needle biopsy (SNB) with fluoroscopy, ultrasound, or CT guidance. Video-assisted thoracoscopic biopsy, GPS guided biopsy.

Bronchoscopic biopsy has also evolved into endobronchial ultrasound (ERUS) biopsy, electromagnetic navigation bronchoscopic biopsy.

At the present time, these modalities of SLN biopsy produced 80 % improvements over skinny needle biopsy.

What to do if SPN is a biopsy proven malignant tumor.

Surgical resection is the treatment of choice.

If the patient is not a candidate for surgical resection but has biopsy proven malignancy, then the following options are available.

External radiation therapy, Stereotactic radiosurgery, Percutaneous radiofrequency ablation.

Single Pulmonary Nodules are mostly asymptomatic when initially detected for unrelated health reasons or during lung cancer surveillance programs for chronic smokers, and the patients are more anxious than sick. A timely investigation and proper counseling must be provided. Most SLN are benign but benign lung tumors can cause pneumonia, lung abscess or hemoptysis and in rare instances turn malignant over years if not properly followed.

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