CT–Pathology Comparisons

Rheumatoid pulmonary nodule is pathologically identical to subcutaneous rheumatoid nodule. They contain three histologically distinct zones: central fibrinoid necrosis, surrounding palisading epithelioid cells, and an outer zone of lymphocytes, plasma cells, and fibroblasts [12]. The necrotic central zone becomes cavitary or cystic, likely with the resolution of necrosis and subsequent inflation resulting from airflow in the lumen. Therefore, patients exhibit rheumatoid pulmonary nodules in various stages from new nodules with central necrosis to older nodules with cavitary or cystic changes.

Patient Prognosis

Rheumatoid lung nodules may remain stable, regress spontaneously, or enlarge. Depending on the clinical circumstances, serial radiographic follow-up or surgical resection may be required.

Cavitary Metastasis

Pathology and Pathogenesis

Cavitation in pulmonary metastases is thought to be uncommon. The primary sites were the large intestine, opposite lung, cervix, stomach, esophagus, pancreas, larynx, and mesenchymal tumors. It seems that the principal cause of necrosis and subsequent cavitation in metastatic tumors of the lung is interference with their blood supply by vascular involvement [13].

Symptoms and Signs

Significant number of patients with cavitary lung metastasis is asymptomatic. Hemoptysis can occur. Nonspecific symptoms including cough, vague chest discomfort, and dyspnea can result from a very large tumor burden. Constitutional symptoms such as weight loss, anorexia, and generalized weakness may be accompanied.

CT Findings

CT finding of cavitary metastasis consists of multiple nodules with or without cavitation (Fig. 23.2). The size of nodules range from a few millimeters to several centimeters in diameter, and nodules are usually of varying size. They tend to be most numerous in the outer third of lungs, particularly the subpleural regions of the lower zones, and have a random distribution within the secondary pulmonary lobules [14, 15]. Most nodules are round and have smooth margins. They may be lobulated, however,

and have irregular margins. The wall of cavitary metastatic nodule is generally thick and irregular, although thinwalled cavities can be found with metastases from sarcomas and adenocarcinomas [7].

CT–Pathology Comparisons

Please note section “Cavity” in Chap. 12 and section “Pulmonary Metastasis” in Chap. 19.

Patient Prognosis

Prognosis of the patients with cavitary lung metastasis is poor since the primary tumor is not highly responsive to anticancer chemotherapy.

Cysts

Definition

A cyst is a round parenchymal lucency or low-attenuating area with a well-defined interface with normal lung. Cysts have variable wall thickness but are usually thin walled (<2 mm). The cysts usually contain air but occasionally contain fluid or solid material [16] (Fig. 23.3).

Diseases Causing Multiple Cysts

Many diffuse lung diseases may manifest cysts as the primary abnormality [17, 18]. Lymphangioleiomyomatosis (LAM) (Fig. 23.3) and Langerhans cell histiocytosis (LCH) are the most common to present with diffuse lung cysts. Other interstitial lung diseases that may cause multiple cysts include lymphocyticinterstitialpneumonia(LIP)(Fig.23.4),desquamative interstitial pneumonia (DIP), subacute hypersensitivity pneumonitis, and amyloidosis. Cystic pulmonary metastasis

(angiosarcoma) (Figs. 23.5 and 23.6) and Birt–Hogg–Dube syndromealsocausemultiplepulmonarycysts.Honeycombing cysts in various interstitial lung diseases (usual interstitial pneumonia, nonspecific interstitial pneumonia, asbestosis, chronic hypersensitivity pneumonitis, advanced fibrotic sarcoidosis) also appear as multiple pulmonary cysts (please note section “Cyst” in Chap. 12 and section “Honeycombing with Subpleural or Basal Predominance” in Chap. 17).

Distribution

Please note section “Cyst” in Chap. 12 and section “Honeycombing with Subpleural or Basal Predominance” in Chap. 17.

Fig. 23.3 Lymphangioleiomyomatosis in a 37-year-old woman. (a–c) Lung window images of thin-section (1.5-mm section thickness) CT scans obtained at levels of aortic arch (a), inferior pulmonary veins (b), and liver dome (c), respectively, show multiple variable-sized air-filled cysts in both lungs. Please note involvement of lung bases that are spared in Langerhans cell histiocytosis. (d) Low-magnification (×40)

photomicrograph of surgical lung biopsy specimen depicts a cystic lesion (CYST) and its wall composed of spindle or ovoid smooth muscle cells (arrows). (e) High-magnification (×100) photomicrograph discloses clearly cystic wall composed of spindle or ovoid smooth muscle cells (arrows)

Clinical Considerations

Please note section “Cyst” in Chap. 12. LAM is associated with tuberous sclerosis (seizure, skin lesions) and is more common than sporadic or lone LAM [19]. Cystic

pulmonary metastases occur most frequently in tumors of epithelial origin and less frequently in tumors of mesenchymal (angiosarcoma, leiomyosarcoma, synovial cell sarcoma, epithelioid cell sarcoma, and endometrial stromal sarcoma) origins [20].

Fig. 23.4 Lymphocytic interstitial pneumonia in a 37-year-old man with Sjögren’s syndrome. (a, b) Lung window images of thin-section (1.5-mm section thickness) CT scans obtained at levels of aortic arch (a) and right upper lobar bronchus (b), respectively, show ground-glass opacity nodules or ground-glass opacity in both lungs along bronchovascular bundles or along subpleural lungs. Also note cystic lung

lesions (arrows). (c) Low-magnification (×40) photomicrograph of surgical lung biopsy specimen depicts peribronchiolar dense fibrosis and scanty lymphocyte aggregations (arrowheads). Such changes are also seen in interlobular septa (open arrows) and subpleural region. Please note cystic changes (arrows) of alveoli associated with bronchiolar fibrosis and inflammation