Clinicopathological findings of focal organizing pneumonia: a retrospective study of 37 cases

Abstract

Background and objective: Focal organizing pneumonia (FOP) is an uncommon disease. The etiology, and in particular the disease's relationship with infection and the incidence of idiopathic FOP, is relatively unknown. The aim of this study is to review clinical, radiological and pathological features of patients with organizing pneumonia (OP) presenting solitary lesions and to analyze possible causes.

Methods: We retrospectively reviewed 37 surgical lung biopsy or resection cases of pathologically confirmed FOP over a period of 10 years.

Results: Microscopically, 17 cases showed OP with neutrophilic infiltration or abscess, 11 with epithelioid cell granulomas or scattered multinucleated giant cells, 2 with greater eosinophilic infiltration, and the remaining 7 cases met the diagnostic criteria for pathological cryptogenic OP (COP). The 37 cases of FOP included 22 men and 15 women, aged 29-76 years, and 17 cases had a history of smoking. Cough, fever, sputum, chest or back pain and hemoptysis were the main symptoms. Seven cases were asymptomatic. The diameters of the lesions ranged from 0.2-6.0 cm (median, 3.0 cm). Fever (9/30), high-sensitivity C-reactive protein elevation (9/17) and abnormalities in pulmonary function test (8/24) existed in focal secondary OP (FSOP) patients, but these symptoms were rarely observed in focal COP (FCOP) (0/7, 1/7 and 0/7 cases, respectively). However, no statistically significant differences were found between the FSOP and FCOP.

Conclusions: Histologically, secondary factors exist in the majority of FOP cases. Idiopathic FOP is found in a minority. With respect to secondary FOP, acute infection and granulomatous inflammation are the main causes. Surgical resection alone appears sufficient for the management of FOP.

Keywords: Focal organizing pneumonia; cryptogenic; secondary.

Figure 1

CT scan of the chest, a 18.0 mm × 16.0 mm opacity with spiculated margins was present in the basal segment of the right lower lobe.

Figure 2

FSOP showing connective tissue polyps in the alveolar lumen in the lesion, but neutrophilic infiltration can be observed in the lesion (the upper left corner). (H & E, × 150).

Figure 3

Another FSOP case, with the same morphologic features as FIG 2, but scattered multinucleated giant cells can be observed in the lesion (the lower left corner). (H & E, × 150).

Figure 4

FCOP showing connective tissue polyps in the alveolar lumen in the lesion with lymphocytic infiltration in the alveolar septum and a slightly widened alveolar septum. (H & E, × 150).