Lung Hamartoma Imaging

What Is Hamartoma?

Hamartoma is a benign (non-cancerous) growth. Tissues from a particular organ in the body may grow aberrantly, forming a tumor-like growth known as a hamartoma. Although the cells are not abnormal in hamartoma, they tend to grow abnormally, resulting in a disorganized mass. A hamartoma may occur in any organ, such as the lungs, skin, heart, brain, breast, or other organs. They tend to grow slowly and are more commonly found in males. Few are hereditary, while others may be associated with certain syndromes.

Hamartomas are usually asymptomatic unless they increase in size or are close to vital structures. Hence they are incidentally found in imaging studies which may be acquired for another diagnostic purpose. In a few cases, hamartomas may sporadically decrease in size, thus requiring no treatment; however, some may cause fatal complications. Hamartomas do not spread to other parts of the body. However, imaging tests are crucial as these benign tumors very much resemble any cancerous growth. In imaging studies, certain characteristic features of these hamartomas can distinguish them from malignant neoplasms. Biopsy offers a confirmatory and conclusive diagnosis.

What Are the Types of Hamartoma?

Hamartomas can be categorized based on the site where they occur. They are described below:

• Breast: Breast hamartomas contribute to 5 % of the breast lump.

• Skin: Hamartomas can occur anywhere on the skin, such as the face, lips, or even throughout the body, where an associated syndrome can be suspected.

• Heart: Hamartomas in the heart are the most common benign tumor in children. It may even result in cardiac failure.

• Lungs: Pulmonary (lung) hamartomas are the most common type. They may result in airway obstruction, pneumonia, or bronchiectasis.

• Brain: Hamartomas in the brain are most commonly found in the hypothalamus (a vital area in the center of the brain). It could result in seizures, hormonal imbalances, and behavioral changes.

• Kidneys: Hamartomas of the kidneys usually result in kidney dysfunction.

• Spleen: Hamartomas of the spleen may result in chronic abdominal pain.

What Is a Lung Hamartoma?

Lung hamartomas are benign tumors of the lungs caused by abnormal proliferation of normal tissues such as fat, epithelium, muscle, or cartilage native to the lung. The cells are normal, but their abnormal growth results in the formation of a disorganized mass (tumor), thereby negating the organ architecture. Pulmonary hamartomas are the most common benign lung tumors. They are more common in adults, with a rare incidence in the pediatric population. They are usually present in the peripheral lung tissues; however, a few cases may also occur in the central chest wall. Endobronchial (within the bronchus) hamartomas are rare; however, they may be symptomatic. These hamartomas usually are slow growing and hence asymptomatic in the initial stages. They are commonly found in males, usually in the fifth or sixth decade of life.

What Are the Causes of Lung Hamartoma?

The exact cause of hamartoma is still debatable; however certain theories suggest genetic predilection. Hamartomas are considered developmental anomalies as their growth rate is similar to the native tissue where they arise. Certain hereditary syndromes associated with hamartomas are:

• Tuberous Sclerosis: A genetic disorder characterized by benign tumors throughout the body.

• Cowden Syndrome: A genetic condition with multiple hamartomas on the skin and mucous membranes with an increased risk of developing cancers.

• PTEN (Phosphatase and Tensin Homolog) Hamartoma Tumor Syndrome: Occurs due to mutation of phosphatase and tensin homolog gene.

• Peutz-Jeghers Syndrome: Hamartomas in the gastrointestinal tract, also known as polyps.

What Are the Symptoms of Lung Hamartoma?

Lung hamartomas are usually asymptomatic and found incidentally on a chest x-ray or other diagnostic procedure. However, a few associated symptoms are:

• Persistent cough.

• Coughing or spitting of bloody mucus if the hamartoma impinges on blood vessels.

• Difficulty in breathing.

• Fever.

• Wheezing.

• Expectoration (cough with mucus).

• Characteristic respiratory sounds (coarse crackles during inspiration).

The patient is symptomatic if the hamartoma is larger or near critical anatomical structures.

What Are the Complications of Lung Hamartoma?

Though lung hamartomas are asymptomatic, some patients may experience fatigue, chest pain, shortness of breath, persistent cough, and other symptoms which may affect their quality of life. These pulmonary symptoms mimic a cardiovascular or a pulmonary condition such as heart failure and thus may potentially be overlooked. The critical location of a hamartoma may also increase the possibility of pneumonia (lung infection), atelectasis (partial or complete collapse of the lung), or pneumothorax (collapsed lung). In addition, endobronchial hamartomas could result in airway obstruction. Hence imaging techniques are crucial to diagnose hamartomas and distinguish them from cancerous lesions.

What Are the Imaging Tests Used to Diagnose Lung Hamartomas?

Diagnostic imaging can be used to assess the severity of the condition and also aid in delineating the management protocol. In addition, since hamartomas are associated with genetic conditions, screening tests may help identify the conditions and assess the risk of developing cancer. The diagnostic workup is given below:

• Chest X-Ray: Chest x-ray is the most straightforward and non-invasive diagnostic procedure. It is a sought-after tool specifically for an emergency diagnosis as the results are quick and direct. Pulmonary hamartomas are incidentally discovered on a routine chest x-ray as a well-defined, circular mass (coin-shaped) with smooth or lobulated margins. Calcification, if present, may appear popcorn shaped or comma-shaped. However, a chest x-ray is not very specific if the mass comprises fat or if there are multiple nodules. Advanced cases may demonstrate bronchial obstruction or signs of infection.

• Computed Tomography: Computed tomography is the preferred diagnostic tool for pulmonary nodules. It is more sensitive than an x-ray to characterize the lesion. The presence of a well-circumscribed lesion with sharp, delineated margins with intranodular fat and the characteristic popcorn-like calcifications are diagnostic features of pulmonary hamartoma. High-resolution CTs are more specific in diagnosing lung hamartomas.

• Magnetic Resonance Imaging (MRI): MRI is considered more specific and sensitive to diagnosing pulmonary hamartomas. The varying signal intensities confirm the presence of fat or calcification within a well-circumscribed nodule.

• Ultrasound: Transthoracic ultrasound is beneficial and vital in image-guided biopsy for a more precise diagnosis.

• Nuclear Imaging: Although uncommonly used, the positron emission tomography (PET) scan has increased sensitivity to diagnose and differentiate hamartoma from any malignant neoplasm. It is a radioactive imaging procedure that uses a radiotracer 18-FDG (fluorodeoxyglucose) which is a glucose analog. It has a high affinity to glucose that is found abundantly in rapidly dividing cells, such as tumor cells, as they require more energy. As a result, the tracer accumulates in the tumor cells and can be imaged using a scanner.

Conclusion:

Lung hamartoma is a benign and asymptomatic condition with an excellent prognosis if treated promptly. Diagnostic imaging becomes crucial in symptomatic patients to detect and rule out any malignancy. Imaging is also essential in asymptomatic patients for periodic screening and conservative observation.