Calcified Lung Nodules: A Diagnostic Challenge in Clinical Daily Practice

Abstract

Calcified lung nodules are frequently encountered on chest imaging, often as incidental findings. While calcifications are typically associated with benign conditions, they do not inherently exclude malignancy, making accurate differentiation essential. The primary diagnostic challenge lies in distinguishing benign from malignant nodules based solely on imaging features. Various calcification patterns, including diffuse, popcorn, lamellated and eccentric, provide important diagnostic clues, though overlap among different conditions may persist. A comprehensive diagnostic approach integrates clinical history with multimodal imaging, including magnetic resonance and nuclear medicine, when necessary, to improve accuracy. When imaging findings remain inconclusive, tissue sampling through biopsy may be required for definitive characterization. This review provides an overview of the imaging features of calcified lung nodules, emphasizing key diagnostic challenges and their clinical implications.

Keywords: calcification pattern; chest CT; lung nodules; pulmonary calcifications.

Figure 1

Different patterns of calcification in a pulmonary nodule.

Figure 2

Composite image from a CT scan demonstrating a solitary small, well-defined nodule with smooth margins, fat-content and typical pop-corn calcifications. The presence of both intralesional fat and calcifications is considered definitively diagnostic for hamartoma (a). Pattern of calcification (b).

Figure 3

Chest X-ray shows a uniformly calcified lung nodule in the peripheral region of the right lower lobe (a). CT confirms the presence of a nodule with diffuse calcification, consistent with a Ghon focus, associated with ipsilateral calcific lymph nodes, forming the Ranke complex. The Ghon focus represents a site of primary tuberculosis with a fibrotic scar that may eventually calcify (b,c). Pattern of calcification (d).

Figure 4

Chest X-ray shows a calcified lung nodule in the central region upper right lobe (a). Coronal HRCT multiplanar reconstruction confirms the presence of a well-defined nodule characterized by lamellate calcification and a necrotic center consistent with tuberculoma. One of the most severe manifestations of Mycobacterium tuberculosis (MTB) infection, tuberculoma often presents as a well-defined nodule with a caseous necrotic core, most commonly affecting the lungs and central nervous system (b). Satellite nodules are present in up to 80% of cases. Pattern of calcification (c).

Figure 5

Patient with previous history of severe varicella pneumonia. HRCT shows bilateral diffuse ill-defined calcified nodules. Scattered diffuse micronodular calcifications are an uncommon late sequela of VZV pneumonia (a,b). Pattern of calcification (c).

Figure 6

CT scans of a Patient with a diagnosis of sarcoidosis demonstrating multifocal nodules characterized by central calcifications (a–c) and calcified lymph nodes are present within the mediastinum (d). Mediastinal lymphadenopathy in sarcoidosis is typically bilateral and symmetric; lymph nodes may calcify over time, commonly exhibiting ‘popcorn’, amorphous and punctate calcifications. Pattern of calcification (e).

Figure 7

Multifocal pulmonary nodules, variable in size, with smooth and lobulated contours, some of which are characterized by central calcification in a patient with biopsy-proven amyloidosis (a–c). The nodular parenchymal amyloidosis is commonly characterized by discrete nodules, heterogeneous in size, with subpleural predominance. Pattern of calcification (d).

Figure 8

Metastatic pulmonary calcification due to deposition of excess calcium in a background of normal lung parenchyma (a–c). These nodules are typically located in the upper lobes. HRCT images show fluffy centrilobular ground glass opacities, some of which calcified. Pattern of calcification (d). (Curtesy of E. Bezzon).

Figure 9

CT axial images demonstrate a peripheric lung nodule characterized by spiculated margins, small cavitation and an eccentric calcification; this lesion was a biopsy-proven adenocarcinoma (a,b). Heavy smoker patient with severe confluent centrilobular emphysema. HRCT shows a malignant nodule with a small eccentric calcification in the right upper lobe (c). A spiculated nodule with a relatively fast growth rate must always raise the concern for lung cancer in patients with smoking history. Pattern of calcification (d).

Figure 10

CT demonstrates diffuse calcified nodules in a patient with osteosarcoma (a,b) (Courtesy of M. Mereu). Bone formation and ossification in osteosarcoma and chondrosarcoma can result in calcified metastatic nodules of the lung. Pattern of calcification (c).