Ground-Glass Opacity with Reticulation, but without Fibrosis (Crazy-Paving Appearance)

Fig. 20.2 Usual interstitial pneumonia manifesting as subpleural patchy areas of reticulation and ground-glass opacity without honeycombing cyst in a 62-year-old man. (a) Lung window image of thin-section (1.5-mm section thickness) CT scan obtained at level of liver dome shows patchy areas of reticulation and ground-glass opacity in bilateral lower lung zones. (b) Low-magniÞcation (×4) photomicrograph of surgical biopsy specimen obtained from left

lower lobe discloses heterogeneous areas of inßammation (arrows) and Þbrosis (open arrows) in alveolar walls in terms of time and region. (c) Seven-year follow-up CT demonstrates increased extent of reticulation in both lungs. Also note new area of honeycombing (open arrow). (d) Follow-up CT in coronal reformatted view depicts reticulation predominant abnormalities with lower lung zone predominance. Also note traction bronchiectasis (open arrows)

Ground-Glass Opacity with Reticulation, but without Fibrosis (Crazy-Paving Appearance)

Definition

The crazy-paving appearance consists of a network of a smooth linear pattern superimposed on the area of groundglass opacity (GGO) on high-resolution CT scans (Fig. 20.5). Once thought as speciÞc Þnding for pulmonary alveolar proteinosis (PAP), currently the crazy-paving appearance is a nonspeciÞc Þnding seen in a variety of interstitial and airspace lung diseases [7].

Diseases Causing the Pattern

The diseases causing crazy-paving pattern include acute bacterial, viral, or Pneumocystis pneumonia (Fig. 20.6), acute interstitial pneumonia (AIP) or adult respiratory distress syndrome (ARDS), diffuse alveolar damage superimposed on usual interstitial pneumonia (UIP), diffuse alveolar hemorrhage (DAH) (Fig. 20.5), pulmonary interstitial edema, pulmonary alveolar proteinosis (PAP) (Fig. 20.7), nonspeciÞc interstitial pneumonia (NSIP), subacute hypersensitivity pneumonitis (HP), organizing pneumonia, sarcoidosis, lipoid pneumonia

(Fig. 20.8), and diffuse form of mucinous or nonmucinous

Fig. 20.3 Fibrotic nonspeciÞc interstitial pneumonia in a 50-year-old woman. (a) Lung window image of thin-section (1.0-mm section thickness) CT scan obtained at level of liver dome shows patchy areas of reticulation and ground-glass opacity in bilateral lower lung zones. Subpleural sparing (arrowheads), one of important signs that help differentiate usual interstitial pneumonia from this disease on CT, is clearly seen. Also note traction bronchiectasis (open arrows). (b) Low-magniÞcation (×40)

photomicrograph of surgical biopsy specimen obtained from right lower lobe discloses clearly temporal and regional homogeneity; namely, whole alveolar wall shows Þbrotic changes with little lymphocytic inÞltration. Also note few areas (arrows) of lymphocytic inÞltration and thickened vessel walls (arrowhead). (c) Four-year follow-up CT demonstrates slightly increased extent of reticulation in both lungs. Still subpleural sparing (arrowheads) is overt particularly in left lung

adenocarcinoma (AIS, former bronchioloalveolar carcinoma [BAC]) or lung adenocarcinoma [7, 8] (Fig. 20.9).

appearance is usually located in the right middle lobe, lingular division of the left upper lobe, or in both the lower lobes.

In most diseases, lung abnormalities show random and patchy and extensive distribution. In NSIP and organizing pneumonia, the abnormalities usually demonstrate subpleural and lower lung zone predominance. In lipoid pneumonia, the crazy-paving

The speed of disease development may help distinguish among various diseases. For example, acute disease process suggest the diagnosis of Pneumocystis or other infectious pneumonia, ARDS, AIP or acute exacerbation of

Fig. 20.4 Fibrotic nonspeciÞc interstitial pneumonia in a 60-year-old woman. (a) Lung window image of thin-section (1.0-mm section thickness) CT scan obtained at level of cardiac ventricle shows patchy areas of ground-glass opacity and reticulation. Please note involvement of central portion (arrowhead) of lung as well as subpleural lungs, which is somewhat more peculiar to nonspeciÞc interstitial pneumonia than usual interstitial pneumonia. Also note traction bronchiectasis (arrow). (b) Coronal reformatted imaged demonstrates central involvement (arrowheads) involvement of lung lesions along bronchovascular bun-

dles, not to mention of subpleural lung involvement. Also note traction bronchiectasis (arrow). (c) Low-magniÞcation (×4) photomicrograph of surgical biopsy specimen obtained from right lower lobe exhibits uniform interstitial expansion with Þbrosis and little lymphocytic inÞltration. Also note thickened vessel walls (arrowheads). (d) Somewhat closer look (×40) of surgical biopsy specimen discloses clearly temporal and regional homogeneity, namely, uniform interstitial expansion due to Þbrosis. Also thickened vessel wall, which is postinßammatory changes (arrowheads)

UIP, DAH, and interstitial edema, whereas chronic indolent course may indicate the presence of PAP, lipoid pneumonia, and diffuse form of lung adenocarcinoma or

mucinous adenocarcinoma in situ (AIS). Other patient history and clinical presentation may also be useful for helping make a speciÞc diagnosis.