Lymphocytic Interstitial Pneumonia

The pathogenesis of cyst development is unclear, but it may arise from air trapping caused by peribronchiolar smooth muscle proliferation [18]. Small centrilobular nodules correspond to hyperplastic muscle or pneumocyte hyperplasia, and focal areas of GGO may be due to smooth muscle proliferation, hemosiderosis, or pulmonary hemorrhage. Interlobular septal thickening represents edema caused by obstruction of pulmonary lymphatics.

HRCT findings of LIP include areas of GGO, poorly defined centrilobular nodules, and thin-walled cysts with a basal predominance [27] (Fig. 23.4). Although the cysts may vary in size (1–30 mm), they are usually smaller than 30 mm. The cysts are typically less numerous than LAM or Langerhans cell histiocytosis. Other HRCT findings include peribronchovascular thickening, interlobular septal thickening, subpleural nodules, lymphadenopathy, and areas of consolidation.

Patient Prognosis

The management of LAM is basically supportive, including care for recurrent pneumothorax and oxygen for dyspnea. Lung transplantation is the last treatment option. Sirolimus, as an mTOR inhibitor, can be the promising medical therapy [24]. Predicting the prognosis of individual patient is difficult. More advance disease at the time of diagnosis and rapid decline in lung function are the poor prognostic factors.

CT–Pathology Comparisons

The cysts in LIP may result from overdistension of airspaces distal to bronchioles that are partly obstructed by the lymphocytic infiltration [28]. Thickening of bronchovascular bundles, poorly defined centrilobular nodules, and interlobular septal thickening reflect the involvement of perilymphatic interstitium.

Lymphocytic Interstitial Pneumonia

Pathology and Pathogenesis

The definition of LIP by American Thoracic Society/ European Respiratory Society 02 consensus classification is limited to the diseases with extensive alveolar septal infiltration of lymphoid cells based on the concept that LIP is one of the interstitial pneumonias [25]. The definition also excluded many of the previously diagnosed LIPs with predominant involvement of interstitium other than alveolar septa such as bronchovascular bundles and interlobular septa, which should be called diffuse lymphoid hyperplasia (Fig. 23.4).

Symptoms and Signs

The majority of patients with LIP are women. The onset of symptoms typically occurs between the ages of 40 and 70 years [26]. Patients present with respiratory symptoms including cough and slowly progressive dyspnea, sometimes associated with pleuritic chest pain. Systemic symptoms such as weight loss, fever, fatigue, arthralgia, and night sweating are less common. In those patients with Sjögren’s syndrome, dry mouth or dry eye may be observed.

Patient Prognosis

Corticosteroids are commonly employed and provide improvement in 50–60 % of patients. Up to one-third of patients may die within several years of diagnosis from progression of disease or infectious complications related to immunosuppressive therapy. Malignant transformation to lymphoma has been described.

Cystic Pulmonary Metastasis, Particularly

Angiosarcoma

Pathology and Pathogenesis

Pulmonary metastasis of angiosarcomas commonly appears as extensive solid nodules; but, cystic or cavitary pulmonary lesions have also been reported. The cystic wall is composed of alveolar wall structures containing infiltrating spindle cell tumor. The spindle cell tumor comprises slit-like blood vessels harboring internal red blood cells. The tumor cells show strongly positive staining for CD31 and CD34 [29].

Symptoms and Signs

Pulmonary metastasis of angiosarcoma is most frequently from the heart and the pulmonary artery trunk. Hemoptysis