Which features are used to characterize pulmonary nodules on CT imaging?

• A. Size, attenuation, borders, calcification, fat content, and enhancement
• B. Only size matters
• C. Color and texture
• D. Patient symptoms

Answer: (A)

Pulmonary nodules on CT are evaluated by a combination of features that together help distinguish benign from malignant lesions and guide management. The size provides a rough risk estimate: larger nodules carry a higher probability of cancer, though small nodules can also be malignant. Attenuation or density tells you whether the nodule is solid, part-solid, or ground-glass, and helps classify it further as likely benign or potentially malignant when considered with other features. Borders describe how the lesion interfaces with surrounding lung: smooth, well-defined margins favor benign processes, while irregular, spiculated, or lobulated margins raise concern for malignancy due to tumor invasion or desmoplastic reaction. Calcification patterns are informative: certain patterns such as central, laminated, or popcorn calcifications strongly suggest benign etiologies like granulomas or hamartomas, whereas irregular or absent calcification can be more worrisome. Fat within a nodule is a clue to a hamartoma when macroscopic fat is present. Enhancement after contrast can indicate vascularity; nodules that show marked enhancement are more suspicious for neoplastic processes, although enhancement must be interpreted alongside the other features. Considering all these aspects together—size, density, margins, calcification and fat content, and enhancement—provides the most reliable CT-based characterization of pulmonary nodules. For example, a nodule with smooth borders, dense central calcification, and fat content is typically benign, whereas a nodule with spiculated margins and rapid growth would prompt higher concern for malignancy. Color, texture, and patient symptoms do not reliably define nodule nature on CT, so they’re not primary features used for characterization.