Progressive Massive Fibrosis

Fig. 2.4 Lung masses as progressive mass Þbrosis in a 73-year-old man. (a) Lung window of thin-section (1.5-mm section thickness) CT scan obtained at level of the azygos arch shows two masses (arrows) in posterior aspect of both upper lobes. Also note small nodules in both lungs. Combined Þndings of two large masses and surrounding small nodules in upper lung zones are suggestive of progressive massive Þbrosis and pneumoconiotic small nodules. (b) Mediastinal window image demonstrates internal calciÞcations (arrows) within progressive massive Þbrosis. Also

note calciÞed lymph nodes in the mediastinum. (c) Low-magniÞcation (×10) photomicrograph of biopsy specimen obtained from different patient with progressive massive Þbrosis discloses large amount of Þbrous tissue containing black pigments (anthracosis). (d) LowmagniÞcation (×40) photomicrograph shows numerous well-circum- scribed black nodules (arrows) mainly in centrilobular location along bronchovascular bundles. Pigmented Þbrosis (open arrows) adjacent to pleura may be seen as pleural-based small nodule at thin-section CT

Progressive Massive Fibrosis

Pathology and Pathogenesis

PMF develops in a background of simple coal workerÕs pneumoconiosis (CWP) (Fig. 2.4). PMF is identiÞed as zones of pigmented Þbrosis that tend to be bilateral and distributed in the upper lobes posteriorly. There is replacement of lung tissue by Þbrosis, with interspersed, abundant, pigmented coal dusts.

Symptoms and Signs

Shortness of breath is the main symptom of PMF. Cough, sputum, and wheezing sound are often present. Symptoms

and signs of right heart failure are found in severe advanced cases. Acute exacerbation by asthmatic airway narrowing or superimposed pneumonia may develop.

CT Findings

PMF appears as a mass usually with irregular margins and associated with adjacent paracicatricial emphysema and lung parenchymal architectural distortion [5, 17]. They are usually bilateral and symmetric (Fig. 2.4). When present, calciÞcation may be punctate, curvilinear, or massive (Fig. 2.4). Cavitation also can occur as the result of ischemia or superimposed mycobacterial infection. On MR images, PMF appears as a low signal intensity on T2-weighted image,

Fig. 2.5 Lung mass representing actinomycosis in a 60-year-old man. (a) Lung window of thin-section (1.5-mm section thickness) CT scan obtained at level of inferior pulmonary veins shows a 42-mm-sized fusiform mass in the right middle lobe. (b) Mediastinal window image shows a geographic central necrotic area (arrow) within lesion. (c) Gross pathologic specimen obtained with right middle lobectomy

displays area of pneumonic consolidation harboring internal round necrotic cavity (arrows). (d) Low-magniÞcation (×40) photomicrograph discloses parenchymal lesion of chronic inßammation and Þbrosis with many lymphoid follicles (arrows). Within abscess cavity, a basophilic material (open arrow) is noted. Inset: magniÞed view of basophilic material, consistent with a sulfur granule

which provides a clue for the differentiation of lung cancer from PMF [12].

CT–Pathology Comparisons

PMF is usually associated with an increased amount of Þbrous tissue and foci of necrosis (Fig. 2.4). Because of Þbrous tissue within PMF, most lesions appear as a low-signal-intensity lesion on T2-weighted image. Necrosis within PMF appears as a focal hyperintense area within PMF on T2-weighted image and low-attenuation area on CT. On enhanced MR images, rim enhancement is present in more than half of cases,

which is caused by collapsed alveoli secondary to emphysema. The remaining lesions do not enhance. This lack of enhancement is thought to reßect the hypovascular nature of the hyaline collagenous tissue of PMF lesion [12].

Patient Prognosis

Since lung Þbrosis is irreversible, prognosis is grave. Patients should be removed from further exposure. Improvement of lung function by bronchodilators and prevention of pneumonia are very important in the management of patients with PMF [18].