OP is rare. The exact aetiology of this inflammatory reaction remains unclear [11]. OP does not exhibit a sex predilection and is more common in older people, with a mean age of onset of 50–60 years [12]. Rare cases have been reported in children. OP is clearly not related to smoking [10]. Lazor et al. reported that OP is more prevalent in non-smokers or ex-smokers, and the proportion was higher among females [13]. In our study, the mean age of patients was 61.25 ± 11.33 (31–82) years, 17 (70.8%) patients were male, and 18 (75.0%) patients were non-smokers or ex-smokers.
Patients may remain asymptomatic in 30 to 70% of cases [14]. Common symptoms included cough, dyspnoea, fever, weakness, pleuritic chest pain, weight loss and haemoptysis [15, 16]. OP is characterized by a mild flu-like illness with nonspecific symptoms [3]. A diagnosis of OP should be considered in patients with a suspected infective pulmonary disorder not responding to antibiotic therapy [17]. In our patients, the most common symptoms included cough, sputum, fever, shortness of breath, and chest pain, haemoptysis, and weakness. Blood tests and pulmonary function test (PFT) do not make a significant contribution to the diagnosis of OP. In the present study, normal blood test in 15(62.5%) patients, and normal PFT in 20 (83.3%) patients.
There are no specific radiological signs for OP. The most typical imaging pattern of OP is a migratory bilateral patchy alveolar infiltrate [14, 18, 19]. Niksarlıoğlu et al. reported that consolidation was observed in 76.6% of their cases [12]. Maimon et al. found that consolidation was present in 77% of their cases, 86% had ground glass opacities (GGO), and 32% had nodules [20]. Similar to the previous studies, consolidation was observed in 12 (50%) and mass-like lesions were observed in 6 (25%) of our cases.
Spontaneous remission of OP is rare, therefore, the diagnosis of OP typically requires treatment if the patient is symptomatic [21, 22]. OP exhibits rapid clinical, imaging and functional improvements with corticosteroid treatment. Some cases with mild or recurrent OP have good response treated with macrolide [23]. Series of OP associated with rheumatoid arthritis have described good results when treated with methotrexate, cyclophosphamide and azathioprine [24]. Others series show that tocilizumab could be a therapeutic alternative in refractory OP associated with systemic lupus erythematosus (SLE) [23, 25]. Relapses are common upon corticosteroid dose reduction or treatment suspension, thus often leading to prolonged treatment [26,27,28]. Recurrence rates vary between 9 and 58% [10, 12, 29]. However, long-term corticosteroid treatment often results in significant side-effects, such as gastrointestinal bleeding, bone fracture, diabetes mellitus, arterial hypertension, upper respiratory tract infections, urinary tract infections and body weight increase [30, 31]. In our study, 14 patients were treated by surgery because cannot tolerate the side effect of steroid.
OP is often found in the shadows of lung cancer [32, 33]. The coexistence of OP with lung cancer has been reported [34]. Zhao’s study of 45 patients with lung cancer concluded that OP lesions may resemble lung carcinoma, and OP may be misdiagnosed as a malignancy [1]. Zhao sought to determine CT features that could differentiate OP from lung carcinoma, however, they concluded that small OP lesions may resemble lung carcinoma [18]. In our study, the main radiological manifestation was consolidated, mass-like lesion and GGO. CT scans revealed lesions with irregular margins (41.7%), air bronchogram (29.2%), significant enhancement (25%), lymphadenectasis (20.8%), pleural effusion (12.5%), and pleural indentation (8.3%). These features also represent typical manifestations of lung cancer on imaging modalities. Three patients were direct treated by surgery because suspected lung cancer according to the image. After the development of OP, its pathological changes are irreversible, and loss of normal organizational structure and function is observed. The main component of OP is fibrous tissue. Although the lesion size does not initially increase for a short period of time, it will not shrink or be absorbed. Previous studies have indicated that it may lead to scarring or cancer [35, 36]. So, we think surgery should be performed if the patient cannot tolerate the side effect of steroid or had not responded to treatments.
Complete lesion resection with preservation of uninvolved pulmonary parenchyma remains the fundamental goal in the surgical treatment of OP. If surgical management confirmed, small-range pneumonectomy should be performed, such as segmentectomy or wedge resection, to preserve as much of the functional lung tissue as possible. Hilar lymphadenectomy cannot be recommended as a routine procedure for the treatment of OP. For larger lesions or the mass is located at the hilum, lobectomy can be performed. The frozen pathological sections should be examined during the operation to avoid extending the resection. In our study, 24 patients were treated by surgery. Three patients were treated by surgery because the family history of lung cancer, 7 had not responded to corticosteroid therapy, and 14 cannot tolerate the side effect of steroid. We performed 11 wedge resections, 9 segmentectomy, and 4 lobectomies. We performed 4 lobectomies because those mass is large and close to the hilum of the lung, and wedge resection is very difficult. Among these procedures, VATS was utilized in 20(83.3%) cases, and the postoperative hospitalization time was 3.67 ± 1.13 [3,4,5,6,7] days. We are following them 59.1 ± 34.5 months (range 2 to 134 months). There were no obvious discomfort and complication. The prognosis was good in all patients after the operation, and no long-term complications were noted.
