The Solitary Pulmonary Nodule

A solitary pulmonary nodule or coin lesion is an approximately round lesion that is less than 3 cm in diameter and that is completely surrounded by pulmonary parenchyma without other abnormalities.

Lesions larger than 3 cm are called masses and are often malignant.

Pulmonary nodules are usually discovered incidentally on CXR but CT scan is considered the required standard.

Radiographic features distinguishing benign and malignant:

Margins - two pattern of margin are relatively specific for cancer.

• Corona radiata/ spiculated appearance - very fine linear strands extending 4 - 5 mm outward from the nodule.

• Scalloped border - associated with intermediate probability of cancer.

Calcification - suggest it is a benign lesion.

• laminated or central pattern is typical of granuloma.

• popcorn pattern is seen in harmartomas.

Growth rate - the volume-dobuling time for malignant bronchogenic tumours is rarely less than a month or more than a year.

If the lesion is spherical, a 30 percent increase in diameter represents a doubling of volume.