Focal organizing pneumonia with reversed halo sign

Diagnosis

Focal organizing pneumonia with reversed halo sign </<span class="end-tag" />P

Findings

A chest radiograph (Figure 1) showed pleural thickening in the region of the costophrenic sulcus, enlargement of the hilar and paratracheal lymph nodes, and a mass in the right upper lobe. A CT scan con&#64257;rmed the mass and its solid peripheral margin and heterogeneous center (Figure 2). Bronchoscopy and &#64257;ne-needle aspiration of the right-upper-lobe opacity revealed lymphoid cells. </<span class="end-tag" />P
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>Over the next 3 years, the patient underwent chemotherapy for CLL. A follow-up CT scan of the chest 3 years later showed the same right-upper-lobe lesion, which was unchanged in size and texture. </<span class="end-tag" />P

Discussion

Organizing pneumonia occurs over a wide age range&mdash;most commonly in the &#64257;fth and sixth decades of life&mdash;without a gender preference. Patients have vague symptoms, usually a subacute presentation of fever, nonproductive cough, malaise, weight loss, and mild dyspnea over a time course of weeks to months.<Sup>1 </<span class="end-tag" />Sup>The physical examination often yields lung crackles in the affected areas, but the examination may be normal. On pulmonary function tests, a mild-to-moderate restrictive pattern, reduced carbon monoxide diffusion capacity, and mild hypoxemia are exhibited. Laboratory &#64257;ndings are consistent with an in&#64258;ammatory process, including mild leukocytosis and elevations in C-reactive protein and erythrocyte sedimentation rate. </<span class="end-tag" />P
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>The histopathologic features of organizing pneumonia reveal intra-alveolar and intrabronchiolar polypoid granulation tissue, so-called Masson bodies, with &#64257;broblasts, myo&#64257;broblasts, and loose connective tissue. Sometimes the granulation tissue contains in&#64258;ammatory cells, eg, macrophages, plasma cells, and neutrophils with eosinophilia.<Sup>1,2 </<span class="end-tag" />Sup></<span class="end-tag" />P
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>Chest radiography commonly shows patchy, bilateral lower lobe areas of parenchymal opacity with a bias for the periphery of the lung. Air bronchograms can be present. On CT, several different manifestations of organizing pneumonia have been described. The most common appearance consists of bilateral, patchy, consolidative and ground-glass opacities, which are seen more often in the peripheral and lower lung regions. The dimensions range from a few centimeters to an entire lobe of the lung. Other presentations of organizing pneumonia include focal lesions, ringlike shadows, and nodular, bronchocentric, perilobular, and bandlike opacities. </<span class="end-tag" />P
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>Focal organizing pneumonia may be dif&#64257;cult to distinguish from malignancy. Diagnosis often requires biopsy or resection, which may yield a solitary mass with an irregular margin and spiculation. The mass tends to be &#64258;at or ovoid (rather than rounded) and may contain air bronchograms or may cavitate. It tends to be peripheral in location and may be in contact with the pleura. </<span class="end-tag" />P
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>A linear pattern of organizing pneumonia occurs in isolation or along with other patterns. It is seen as 2-cm or longer bands or arcs of opacity that measure at least 8 mm in width. Its margins may be smooth or irregular. Air bronchograms may be present. These bands may either extend toward the lung periphery in a radial fashion associated with bronchi or may appear peripheral without association with bronchi. </<span class="end-tag" />P
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>A recently described unusual appearance of organizing pneumonia consists of rings and crescents; initially 2 cases were described by Voloudaki et al.<Sup>3 </<span class="end-tag" />Sup>This appearance has also been dubbed the &ldquo;reversed halo sign&rdquo; (Figures 1 through 4). It consists of a central area of ground-glass opacity that is surrounded completely or partially by a ring or crescent of consolidation. Histologically, the central ground-glass area corresponds to alveolar septal in&#64258;ammation and cellular debris, while the outside ring or crescent represents granulation tissue within alveoli and bronchioles (Figures 5 and 6). </<span class="end-tag" />P
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>Historical review of CT scans from patients with biopsy-proven organizing pneumonia by Kim et al<Sup>4 </<span class="end-tag" />Sup>revealed a ring or crescent pattern in 6 of 31 patients.<Sup>4 </<span class="end-tag" />Sup>A small comparison group of patients with biopsy-proven Wegener&rsquo;s granulomatosis, bronchioloalveolar carcinoma, eosinophilic pneumonia, or Churg-Strauss syndrome failed to show any similar CT &#64257;ndings of a ring or crescent pattern. This suggests that the reversed halo, ring, or crescent patterns are more speci&#64257;c for organizing pneumonia than are the most commonly seen patchy ground-glass and consolidative patterns. </<span class="end-tag" />P
><p><B>CONCLUSION </<span class="end-tag" />B></<span class="end-tag" />p><P

>The reverse halo sign is an uncommon but relatively speci&#64257;c radiologic sign of cryptogenic organizing pneumonia. Radiologists should become familiar with this relatively new addition to the spectrum of imaging &#64257;ndings in organizing pneumonia. </<span class="end-tag" />P

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>Cordier JF. Organising pneumonia. Thorax. 2000;55:318-328. </<span class="end-tag" />LI
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>Oikonomou A, Hansell DM. Organizing pneumonia: The many morphological faces. Eur Radiol. 2002;12:1486-1496. </<span class="end-tag" />LI
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>Voloudaki AE, Bouros DE, Froudarakis ME, et al. Crescentic and ring-shaped opacities. CT features in two cases of bronchiolitis obliterans organizing pneumonia (BOOP). Acta Radiol. 1996;37:889-892. </<span class="end-tag" />LI
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>Kim SJ, Lee KS, Ryu YH, et al. Reversed halo sign on high-resolution CT of cryptogenic organizing pneumonia: Diagnostic implications. AJR Am J Roentgenol. 2003;180:1251-1254