Fig. 8.2 Cryptogenic organizing pneumonia showing reversed halo sign in a 58-year-old woman. (a, b) Lung window images of thin-sec- tion (2.5-mm section thickness) scans obtained at levels of the suprahepatic inferior vena cava (a) and liver dome (b), respectively, show multifocal areas of ground-glass opacity in both lungs. Also note reversed halo sign area (arrows). (c) Low-magniÞcation (×8) photomicrograph demonstrates somewhat denser area of consolidative area

(arrows) and less dense area (open arrows) of interstitial inßammatory cell inÞltration areas. Combination of these denser and less dense areas helps form reversed halo sign. (d) High-magniÞcation (×100) photomicrograph discloses polyps (arrows) of Þbroblast tissue within lumens of respiratory bronchioles, alveolar ducts, and alveoli. The interstitium is moderately thickened by mononuclear inßammatory cell inÞltrates

improvement and normalization of the chest lesion is observed in two-thirds of patients. Spontaneous improvement also has been reported. Relapse may occur when the corticosteroids are tapered. Rapidly progressive fatal form can have a clinical course of acute interstitial pneumonia, showing a high mortality [14].

Pulmonary Mucormycosis

Pathology and Pathogenesis

The characteristic pathology features of pulmonary mucormycosis are extensive parenchymal and vascular invasion by mycelia, with resultant hemorrhagic infarction. The organisms can be differentiated from Aspergillus because they are wider, nonseptate, fragmented, and having irregular branching points, often at 90¡ angles [15].

Symptoms and Signs

Pulmonary mucormycosis is an important opportunistic mycosis in severely immunocompromised patients with hematologic malignancies and recipients of stem cell transplantation [15]. The clinical presentations of pulmonary mucormycosis are similar to those caused by Aspergillus. Concomitant sinus infection, oral necrotic lesions in the hard palate, and chest wall cellulitis are suggestive of pulmonary mucormycosis. Refractory fever despite broad spectrum antibiotics, nonproductive cough, progressive dyspnea, and pleuritic chest pain are common.

CT Findings

The most common CT Þndings of pulmonary mucormycosis are nodules or consolidation [16]. Consolidations are most commonly posterior, abutting the pleura. They may be

Fig. 8.3 Pulmonary mucormycosis in a 17-year-old woman who had a history of anaplastic large cell lymphoma 5 years ago. (a, b) Lung window images of enhanced consecutive CT scans (5.0-mm section thickness) obtained at levels of the right bronchus intermedius show dense consolidation surrounded by ground-glass opacity (a kind of halo sign). Please note internal reversed halo sign (arrows) formed by central necrosis and peripheral enhancing ring of consolidation. (c) Cut surface

of gross specimen obtained with wide wedge resection of the left upper lobe by using video-assisted thoracoscopic surgery demonstrates invasive fungal consolidative lesion harboring necrotic cavity (arrows). (d) High-magniÞcation photomicrograph (×100) discloses necrotizing pneumonia. Please note fungal organisms that have broad hyphae (arrows), thin wall, and little (pauci) septa

Fig. 8.4 Lymphomatoid granulomatosis in a 70-year-old man showing reversed halo sign. Lung window image of CT scan (5.0-mm section thickness) obtained at level of the left lower lobar bronchus shows multiple variable-sized nodules in both lungs. Please also note bilaterally enlarged hilar lymph nodes. Some nodules show reversed halo sign (arrows)

Table 8.1 Common diseases manifesting as reversed halo sign

Note: ANCA antineutrophil cytoplasmic antibody