Isolated middle lobe atelectasis: aetiology, pathogenesis, and treatment of the so-called middle lobe syndrome.

Abstract

ABSTRtACT Isolated atelectasis of the middle lobe has been known for many years as the "middle lobe syndrome". Several clinical studies have shown that it may be caused by malignant tumours. A 10-year study of 135 patients with isolated middle lobe atelectasis is presented. Fifty-eight patients (43 %) had malignant tumours. Of 38 who had a thoracotomy, lung resection was possible in 25.In 20 patients regional or systemic dissemination of the tumour had been diagnosed before operation. Seventy-seven patients had benign diseases, of which 74 were non-specific infections. Bronchography was performed in 46 of these cases, and all had abnormal findings in the middle lobe, eight revealing definite bronchiectasis. In three cases tuberculosis was found. In 16 cases the benign diagnosis was established at thoracotomy. Only three patients out of 58 with malignant tumours lived more than five years. Atelectasis of the middle lobe is always a sign of potential malignancy especially in patients with a previously normal chest radiograph.

Middle Lobe Syndrome: A Review of Clinicopathological Features, Diagnosis and Treatment

“…The most common cause of extrinsic compression of the right middle lobe bronchus is enlargement of the peribronchial lymph nodes [4]. This can be due to granulomatous infections such as histoplasmosis that cause adenopathy, but other fungal infections and typical and atypical mycobacterial infections are also well-described etiologies of obstructive MLS [3,10,11,12,13,14]. Furthermore, adenopathy due to sarcoidosis or lymph node metastases has also been described in obstructive MLS [3].…”

“…Obstructive MLS can be caused by endobronchial lesions or extrinsic compression of the right middle lobe bronchus. Tumors, both benign and malignant, have been estimated to account for about one quarter of cases of MLS [3,9], but it is important to note that many MLS studies have excluded patients with identifiable neoplasms [1,3]. Among the benign tumors that can cause obstruction are hamartomas, but malignant causes include primary lung cancer and metastases [3,9].…”

“…This can be due to granulomatous infections such as histoplasmosis that cause adenopathy, but other fungal infections and typical and atypical mycobacterial infections are also well-described etiologies of obstructive MLS [3,10,11,12,13,14]. Furthermore, adenopathy due to sarcoidosis or lymph node metastases has also been described in obstructive MLS [3]. Other less common causes of obstruction of the right middle lobe bronchus include aspirated foreign objects (particularly in children), broncholiths that erode endobronchially from adjacent calcified lymph nodes, inspissated mucus associated with cystic fibrosis or allergic bronchopulmonary aspergillosis, and endoluminal granulomas associated with sarcoidosis [15,16].…”

“…Tumors, both benign and malignant, have been estimated to account for about one quarter of cases of MLS [3,9], but it is important to note that many MLS studies have excluded patients with identifiable neoplasms [1,3]. Among the benign tumors that can cause obstruction are hamartomas, but malignant causes include primary lung cancer and metastases [3,9]. The most common cause of extrinsic compression of the right middle lobe bronchus is enlargement of the peribronchial lymph nodes [4].…”

“…There is limited literature on MLS, probably because of its multiple etiologies, varied presentation and lack of consistent clinical definition [3,4]. The most common definition of MLS is recurrent or chronic collapse of the middle lobe of the right lung.…”