Cellular Nonspecific Interstitial Pneumonia

Pathology and Pathogenesis

The inßammatory process in cellular NSIP is diffuse and uniform, mainly involving the alveolar walls and variably affecting the bronchovascular sheaths and pleura (Fig. 21.1). When air space organization (the organizing pneumonia pattern) is present, it is not uniformly distributed as might occur in organizing infectious pneumonia. When Þbrosis occurs in NSIP, it is usually mild and preserves lung structure. Peribronchiolar metaplasia of variable extent may be seen, but microscopic honeycombing (HC) is characteristically absent [6].

Symptoms and Signs

The typical clinical presentation of NSIP is breathlessness and cough of approximately 6Ð7 monthsÕ duration, predominantly in women, in never-smokers, and in the sixth decade of life [7]. Chest examination reveals bilateral inspiratory crackles in most patients. Digital clubbing is rarely seen in cellular nonspeciÞc interstitial pneumonia. Systemic symptoms, including fever and arthralgia, are frequently observed.

CT Findings

Cellular NSIP is often characterized by the absence of severe Þbrotic changes or HC. The most common CT Þndings of NSIP are GGO (Fig. 21.1) and Þne reticular abnormality [8]. Traction bronchiectasis may be present or absent. All these Þndings have a symmetric lower lung zone distribution. Consolidation sometimes is seen, but is not the primary abnormality of NSIP. If rapidly developing airspace consolidation or GGO is seen in a patient with NSIP, one should consider the possibility of an acute exacerbation or infection [9]. Although cellular NSIP is characterized by the absence of severe Þbrotic changes, imaging features of cellular and Þbrotic NSIP often overlap and there is no reliable way to differentiate between cellular and Þbrotic NSIP [10].

CT–Pathology Comparisons

Cellular NSIP demonstrates prominent inßammation without signiÞcant Þbrosis. Areas of GGO correspond histologically to the areas of interstitial thickening by inßammatory cells and Þbrous tissue (Fig. 21.1), whereas the areas of consolidation are related to areas of cryptogenic organizing pneumonia [11].

Patient Prognosis

Prognosis of cellular NSIP is excellent, with a 10-year survival up to 100 %. Corticosteroids are the main drugs for the treatment.

Desquamative Interstitial Pneumonia

Pathology and Pathogenesis

On scanning magniÞcation, the DIP has an eosinophilic appearance due to the presence of eosinophilic macrophages uniformly Þlling air spaces (Fig. 21.2). Mild interstitial thickening by Þbrous tissue is the rule and is uniform in appearance. When chronic inßammation is evident at scanning magniÞcation, it is centrilobular and associated with respiratory bronchioles [12].

Symptoms and Signs

The clinical presentation of patients with DIP is nonspeciÞc. It consists of chronic cough and dyspnea [13]. Physical examination reveals inspiratory crackles in approximately 60 % and digital clubbing in 25Ð50 % of patients.

CT Findings

The predominant TSCT Þnding of DIP is bilateral areas of GGO with subpleural and basal predominance [14] (Fig. 21.2). Although reticular opacity may be associated with the GGO, HC is uncommon.

CT–Pathology Comparisons

Areas of GGO on TSCT reßect the Þlling of alveolar airspaces by macrophages [15] (Fig. 21.2).

Patient Prognosis

Smoking cessation is the Þrst and most important therapeutic intervention for individuals with DIP who smoke. Pharmacologic therapy with corticosteroids is often used in patients with marked symptoms or signiÞcant impairment of lung function. Spontaneous remission has also been described. DIP can gradually progress, particularly in those who continue to smoke.