Hamartoma

Hamartomas are the most common benign pulmonary tumors and are found in 0.25% of all autopsies.

They are usually incidental findings on chest films, where they appear as round or lobulated solitary lesions typically less than 4 cm in diameter.

They are most frequently encountered in the 6th decade of life.

Although they are benign, a clinical evaluation and diagnosis is necessary for their identification and to rule out other malignancies.

Hamartomas, by definition, are overgrowths of normal mature tissue within their normal organ or tissue of origin.

Therefore, they are best considered a developmental anomaly rather than a true neoplasm.

Pulmonary hamartomas are composed of

a mixture of cartilage (often calcified),

respiratory epithelium,

smooth muscle,

fat,

fibrous connective tissue,

and marrow.

Clinically they may be located endobronchially and produce obstructive symptoms or as well circumscribed nodules within the parenchyma.

They may exhibit slow growth which can be followed by serial chest x-rays.

On section they often contain foci of calcification.

Diagnosis is best accomplished by a conservative investigative techniques such as fine needle aspiration.

Once diagnosed, they do not need to be removed unless there is radiographic documentation of growth, or the mass is producing symptoms based upon its size or location. Cases of malignancy arising from hamartoms are very rare.

Upon microscopic examination, benign, mature cartilage is the predominant component with a mixture of fat cells, mesenchymal elements, and epithelial cells.