Rolled edge sign | Radiology Signs

Answer:

The rolled edge sign is the appearance of a calcified pleural plaque seen en face: the dense calcified perimeter of the plaque is projected tangentially and stands out as a sharp rim, while the thin central portion is projected face-on and appears comparatively lucent, so the lesion looks like a raised-edged disc lying on the lung. The same plaque viewed in profile against the chest wall gives the familiar holly leaf outline with its knobbly, nodular border. Plaques are the commonest manifestation of asbestos exposure and appear after a latency usually exceeding 20 years. Their distribution is characteristic and is the key to recognition: they arise from the parietal pleura over the posterolateral chest wall between the sixth and ninth ribs, over the domes of the diaphragm and along the mediastinal pleura, and they characteristically spare the costophrenic angles and the lung apices. Plaques are markers of exposure only; they do not by themselves cause functional impairment and are not premalignant, though the exposure they indicate carries a risk of mesothelioma and bronchogenic carcinoma. CT is far more sensitive and separates plaques from the two mimics that trouble radiography: extrapleural fat, which is bilateral, symmetric, smooth and of fat attenuation, and the normal serratus anterior and subcostalis muscles seen tangentially. Diffuse pleural thickening, which does involve the costophrenic angle and may cause restriction, is a separate entity.

Why is it called so?

The dense calcified rim projected around a lucent centre gives the impression that the edge of the plaque has been rolled up like the lip of a dish.

Pathophysiology

Inhaled amphibole fibres reach the periphery of the lung and are cleared through the visceral pleura into parietal pleural lymphatic stomata, where they lodge at the sites of preferential drainage over the lower lateral chest wall and diaphragm. The retained fibres provoke a chronic low-grade inflammatory and fibrogenic response with deposition of acellular, basket-weave hyalinised collagen on the parietal pleura, which over decades undergoes dystrophic calcification. Because the plaque is a discrete plate that is thickest at its raised margins and thin in the middle, its radiographic appearance depends entirely on the angle at which the X-ray beam meets it, which is why the same lesion produces a holly leaf in profile and a rolled edge en face.

Alternative names: Rolled edge appearance of a pleural plaque

Other associated named signs: Holly leaf sign of a plaque in profile, the comet tail sign of rounded atelectasis, and shaggy heart border of asbestosis

References

1. Roach HD, Davies GJ, Attanoos R, Crane M, Adams H, Phillips S. Asbestos: when the dust settles an imaging review of asbestos-related disease. Radiographics. 2002;22 Spec No:S167-84. PMID: 12376609.