Fig. 14.1 Air-crescent sign in aspergillomas growing within chronic tuberculous cavities in a 76-year-old man. (a) Chest radiograph shows air-crescent signs (arrows) in both apices. Also note small nodules in the bilateral upper lung zones. (b) Lung window image of thin-section (1.5-mm section thickness) CT scan obtained at level of great vessels demonstrates aspergillomas within cavities disclosing so-called aircrescent signs (arrows) in both lung apices. Also note parenchymal band in the right apex and bullae in both apices

Aspergilloma

Pathology and Pathogenesis

Aspergilloma is the fungus growth in the lumen of a cavity in the lung without invading the tissues (Fig. 14.2). The ball usually forms in an existing cavity, particularly an old tuberculous cavity (Fig. 14.1), bronchiectasis (Fig. 14.2), abscess, or emphysema, or in a congenital cyst. Aspergilloma formation has been observed both in the bronchiectatic lung distal to an obstructing carcinoma and within the cavity resulting from necrosis at the center of a peripheral carcinoma. Microscopically, an aspergilloma consists of a dense network of hyphae (Fig. 14.2), most of which are dead. Only the hyphae at the surface are well preserved.

Conglomeration of intertwined fungal hyphae admixed with mucus and cellular debris appear as non-enhancing soft tissue mass on CT [13] (Fig. 14.2). The mass is separated from the wall of cavity by airspace, resulting in the air-crescent sign, and usually moves with position changes. Thickening of the cavity wall and pleura is due to a hypersensitivity reaction [11].

Patient Prognosis

The natural history of aspergilloma is variable. In majority of cases, the lesion remains stable. The mortality rate from hemoptysis ranges from 2 to 14 %. In asymptomatic patients, no therapy is warranted. There is no consistent evidence that aspergilloma responds to antifungal agents. Bronchial artery embolization should be considered as a temporary measure to control bleeding in patients with lifethreatening hemoptysis. The surgical resection is associated with relatively high morbidity and mortality that ranges between 1 and 23 %, although this seems to have improved over time.

Rasmussen’s Aneurysm

Pathology and Pathogenesis

The involvement of blood vessels in pulmonary tuberculosis inducing obliterative endarteritis leads to the closure of the lumen of the pulmonary and bronchial arteries before their walls have been penetrated. However, caseation sometimes advances too quickly for the artery to become completely blocked, and an aneurysm may form where the

Fig. 14.2 Air-crescent sign in an aspergilloma growing within a dilated bronchus in a 53-year-old man. (a) Lung window image of thinsection (1.5-mm section thickness) CT scan obtained at level of right inferior pulmonary vein shows an aspergilloma showing air-crescent sign within a dilated bronchus (arrows) in left lower lobe. (b) Gross pathology of resected specimen (left lower lobectomy) demonstrates a soft yellow-gray lesion (arrows) within a dilated bronchus. Air is

located between the lesion and airway wall, and the air is the source of air-crescent sign on CT scan. (c) Scanning view exhibits a dilated bronchus (arrows) harboring a fungus ball (arrowheads). (d) Highmagnification (×100) photomicrograph discloses a part of aspergilloma consisting of dense clump of fungal hyphae (arrowheads). Bronchial wall shows chronic inflammation (open arrow)

muscular and elastic coats are destroyed on the side nearer to the cavity [14].

as avidly enhancing nodules located within the walls of tuberculous cavity [16] (Fig. 14.3).

Hemoptysis is the usual presenting symptom and may be life-threatening when it is massive [15]. Otherwise, respiratory symptoms including cough and dyspnea are due to the underlying disease.

Rasmussen’s aneurysm is caused by weakening of the pulmonary artery wall from adjacent cavitary tuberculosis. Progressive weakening and fibrin replacement of the arterial wall result in pseudoaneurysm formation, and subsequent rupture with hemorrhage.

Rasmussen’s aneurysm is a focal dilatation of one of the pulmonary segmental arteries adjacent to tuberculous parenchymal change or chronic tuberculous cavity and is seen

Prognosis of Rasmussen’s aneurysm is not well known since it is a rare disease.

Fig. 14.3 Air-crescent sign in a Rasmussen’s aneurysm in a 34-year- old man. (a) Chest radiograph shows destructive tuberculous lesions in the bilateral upper lung zones in which bullae are also seen. Also note a mass showing air-crescent sign (arrows). (b) Lung window image of thin-section (2.5-mm section thickness) CT scan obtained at level of right inferior pulmonary vein shows a soft tissue mass depicting aircrescent sign (arrows) in lingular division of left upper lobe. Also note

tuberculous lesions appearing as cavitating and noncavitating nodules in the left lung and right middle lobe. (c) Mediastinal window image of enhanced CT scan obtained at same level to (a) demonstrates a highly enhancing lesion of aneurysm (arrowheads) with surrounding air crescent (arrow). (d) Coronal reformatted image (2.0-mm section thickness) exhibits the aneurysm (arrow). (e) Left pulmonary angiogram discloses the aneurysm (arrow) more clearly