Cavity

Definition

A cavity is a gas-Þlled space, shown as a lucency or lowattenuation area, with identiÞable wall (usually >4 mm in thickness) (Fig. 12.1). It can be seen within pulmonary consolidation, a mass, or a nodule. A cavity is usually produced by the expulsion or drainage of a necrotic portion of the lesion via the airways. It may contain a ßuid level [1, 2].

Diseases Causing the Cavity

Cavities are present in a wide variety of infectious and noninfectious processes. Malignancies are the most frequent noninfectious process causing lung cavitary lesion(s) and include primary lung cancer (squamous cell carcinoma) (Fig. 12.1), lymphoma, and Kaposi sarcoma particularly in HIV-infected patients, lymphomatoid granulomatosis, and metastasis from an extrathoracic malignancy. Other noninfectious causes are antineutrophil cystoplasmic antibody (ANCA)-associated granulomatous vasculitis (former WegenerÕs granulomatosis), pulmonary embolism and infarction and necrosis, and Langerhans cell histiocytosis (eosinophilic granuloma) (Fig. 12.2). Infectious conditions comprise bacterial infection (necrotizing pneumonia and lung abscess, septic pulmonary embolism (Fig. 12.3), and nocardiosis), mycobacterial infection (Mycobacterium tuberculosis (Fig. 12.4) and nontuberculous mycobacterial [NTM] pulmonary disease (Fig. 12.5)), fungal infection (aspergillosis (Figs. 12.6 and 12.7), zygomycosis, coccidioidomycosis, and cryptococcosis), and parasitic infection (paragonimiasis) [1] (Table 12.1) (Fig. 12.8).

Distribution

Fig. 12.1 Squamous cell carcinoma in a 69-year-old smoker man. Lung window image of thin-section (1.5-mm section thickness) CT scan obtained at level of suprahepatic inferior vena cava shows a cavitary lesion (arrows) having irregular and variable wall thickness in right lower lobe

mainly in the upper and middle lung zones, sparing the lower lung zones. The presence of a single or multiple large cavitary lesions in the upper lobes suggests the diagnosis of mycobacterial disease [3]. In NTM disease, cavitation is common in the upper lobes and frequently associated with apical pleural thickening and pulmonary emphysema (upper lobe Þbrocavitary form) [4]. In pleuropulmonary paragonimiasis, necrotic or cavitary nodules or masses are usually located in the subpleural or subÞssural areas [5].

Clinical Considerations

In Langerhans cell histiocytosis, the cavitating nodules are associated with noncavitating nodules and are distributed

Cigarette smoking is highly related to pulmonary Langerhans cell histiocytosis, and the cavitating nodules in the disease

Fig. 12.2 Pulmonary Langerhans cell histiocytosis in a 47-year-old smoker woman (20-pack-year smoking history). (a, b) Lung window images of thin-section (1.5-mm section thickness) CT scans obtained at levels of aortic arch (a) and inferior pulmonary veins (b), respectively, show cavitating and noncavitating nodules in both lungs. Also note variable wall thickness of cavitating nodular lesions. (c) Coronal reformatted image (2.0-mm section thickness) demonstrates nodular lesions

with upper and middle lung zone predominance. (d) High-magniÞcation (×100) photomicrograph of surgical biopsy specimen obtained from left upper lobe discloses a cystic lesion (arrows) having relatively thick wall which is composed of numerous Langerhans cells and other inßammatory cells. Also note mild inßammatory cell inÞltration in pericystic interstitium (alveolar walls)

are reversible with corticosteroid or cytotoxic drug therapy [6]. In tuberculous infection, imaging Þndings have implications as for host immune status (e.g., lymph node enlargement and lower lung zone parenchymal opacity in HIV-infected patients) of patients, but whether a patientÕs disease is due to recently transmitted (epidemiologically primary infection) or remotely acquired infection (reactivation tuberculosis) cannot be determined from the radiographic Þndings [7]. The most common risk factor for pulmonary nocardiosis is underlying lung disease such as asthma, bronchiectasis, or chronic obstructive pulmonary

disease. People with systemic immunodeÞciency associated with cancer chemotherapy, HIV infection, organ transplantation, or long-term corticosteroid use are also at increased risk for pulmonary Nocardia infection [1]. Cryptococcal infections are mostly common in immunocompromised patients such as those with AIDS, who underwent organ transplantation, or who have a hematologic malignancy. These infections are relatively rare in immunocompetent patients [8]. Paragonimiasis infection occurs when humans eat infected crabs or crayÞsh containing metacercaria of Paragonimus.

Fig. 12.3 Septic lung in a 58-year-old man with methicillin-sensitive Staphylococcus aureus who has a history of electric burn on his left thigh. (a, b) Lung window images of CT (2.5-mm section thickness) scans obtained at levels of aortic arch (a) and right bronchus intermedius

(b), respectively, show bilateral extensive areas of ground-glass opacity and consolidation. Also note variable-sized cavitary lesions (arrows) in both lungs. Pleural effusions are also seen, bilaterally

Fig. 12.4 Multidrug-resistant pulmonary tuberculosis in a 49-year- old woman. (a, b) Lung window images of CT (2.5-mm section thickness) scans obtained at levels of aortic arch (a) and right upper lobar bronchus (b), respectively, show a large thick-walled cavitary lesion (arrows in a) in volume decreased left upper lobe and another smaller cavity (open arrow) and nodular lesions (arrowheads) in left lower lobe. Also note left pleural effusion and subcentimeter nodules in right upper lobe. (c) Coronal reformatted (2.0-mm section thickness) CT image demonstrates left upper lobe cavity (arrows) and thin-walled cavity (open arrow) and nodular lesion (arrowhead) in left lower lobe.

Please note left pleural effusion. (d) Gross pathologic specimen obtained with left pneumonectomy displays a large cavity (arrows) in the left upper lobe, thin-walled cavity (open arrow) in the left lower lobe, multiple nodules containing caseation necrosis (arrowheads), and marked bronchial thickening due to inßammatory and Þbrotic changes. (e) High-magniÞcation (×100) photomicrograph of pathologic specimen discloses a necrotizing granuloma having palisading epithelioid histiocytes and eosinophilic materials (arrows) on its periphery and central caseating necrotic materials (C). Inset: small necrotizing granuloma

Fig. 12.4 (continued)

Key Points for Differential Diagnosis

1.In cavitary squamous cell carcinoma, the borders of tumor are often irregular or lobulated. The cavities are usually thick walled and have a nodular inner surface. Discordance between the inner and outer walls of a cavitary lesion (e.g., smooth inner walls and uneven outer walls or uneven outer and inner walls and discordant uneven sectors) is more common in peripheral lung cancer cavity, and concordance between the walls (e.g., smooth inner and outer walls or uneven outer and inner walls and concordant uneven sectors) is more common in single pulmonary tuberculous cavity. Thus, analyzing the characteristics of cavitary internal and external walls on CT is valuable in differentiating between peripheral lung cancer cavity and single pulmonary tuberculous thickwalled cavity [9].

C

2.In pulmonary tuberculosis, satellite centrilobular nodules or tree-in-bud patterns suggesting bronchogenic spread usually seen around the cavities. The presence of multiple cavities and young patient age (20s or 30s) suggest multidrug-resistant (MDR) tuberculosis [10].

3.The presence of a cavity on CT of the lung may help exclude the diagnosis of viral infection in immunocompromised patients and lung infection [11].

4.The air-crescent sign in invasive pulmonary aspergillosis, deÞned as crescents of air surrounding nodular lesions, is observed in up to 63 % of patients. The sign, occurring in about half of the patients with recovery from neutropenia, is caused by tissue ischemia and subsequent necrosis due to fungal angioinvasion [12]. Whether a mural nodule within a cavitary lesion is contrast-enhanced or not is one of the most important features in making a

Fig. 12.5 Nontuberculous mycobacterial pulmonary disease of upper lobe Þbrocavitary form (M. intracellulare) in a 64-year-old man. (a) Lung window image of CT scan (2.5-mm section thickness) obtained at level of great vessels shows relatively even cavity wall thickness (arrows) in left apical area. Also note variable-sized nodules. (b) Coronal reformatted image (2.0-mm section thickness) demonstrates

two cavitary lesions (arrows) in left upper lobe. Also note wall thickening (open arrow) of bronchus draining larger cavity. (c) Gross pathologic specimen obtained with left upper lobectomy discloses several thin-walled cavities (arrows), variable-sized granulomas (arrowheads), and bronchiectasis (open arrows)

Fig. 12.6 Invasive pulmonary aspergillosis in a 27-year-old woman with acute myeloid leukemia. (a) Lung window image of CT scan (2.5- mm section thickness) obtained at level of right bronchus intermedius shows a cavitating nodule (crescent sign) (arrow) in lingular division of left upper lobe and cavitating and noncavitating areas (open arrows) of

consolidation in right upper lobe. Also note bilateral pleural effusions. (b) Coronal reformatted image (2.0-mm section thickness) demonstrates multiple cavitating nodules (arrows) showing crescent sign. (c) HighmagniÞcation (×100) photomicrograph of surgical biopsy specimen disclosed fungal organisms (arrows) within cavitated infarction area

differential diagnosis between an intracavitary aspergilloma and a cavitary lung cancer [13].

5. The presence of a Òfeeding vesselÓ sign, in which a distinct vessel is seen leading to the center of a pulmonary nodule, may suggest the diagnosis of septic embolism, but the sign is nonspeciÞc (may be seen in pulmonary metastatic nodules) [14].

6.According to one CT report [8], cavitation within lung lesions in pulmonary cryptococcosis was noted in only four (17 %) of 23 patients. The

lung lesions of cryptococcosis in non-AIDS patients show an indolent course, slowly progressive even without adequate treatment and does not show a rapid resolution even with antifungal treatment [8].

7.Subpleural or subÞssural necrotic nodule with adjacent pleural thickening and subpleural linear opacities (worm migration track) leading to a necrotic nodule can be an important clue in the diagnosis of pleuropulmonary paragonimiasis on CT [5].

Fig. 12.7 Invasive pulmonary aspergillosis in an 11-year-old boy with acute lymphoblastic leukemia. (a, b) Lung window images of CT (5.0- mm section thickness) scans obtained at levels of right bronchus intermedius (a) and liver dome (b), respectively, show multiple nodules (arrows) showing halo sign. Also note a cavitating nodule (open arrow)

in superior segment of left lower lobe. (c) High-magniÞcation (×100) photomicrograph of surgical lung biopsy specimen discloses necrotizing fungal pneumonia with abscess formation. Please note blue fungal hyphae (arrows) in necrotic spaces