Endobronchial Lipoma in a Never-Smoker

Endobronchial lipomas, usually found in the obese and in smokers, can cause patients significant distress with chronic cough, chest pain, dyspnea, and increased infection risk. Here we present a case of a 61 year-old obese, never-smoker gentleman who initially presented with chronic productive cough, hemoptysis, chills and night sweats; and was later found to have a right upper lobe lung parenchymal lesion. Biopsy demonstrated a picture consistent with obstructive endobronchial lipoma.


Introduction
Endobronchial lipomas have been believed to represent 0.1 to 0.5% of all lung tumors or 0.1 to 0.4% of all bronchial tumors, usually presenting in the obese and in smokers [1,2].They can be misdiagnosed as malignant lesions; and although most are fairly benign lesions, they can cause patients significant distress with chronic cough, chest pain, dyspnea, and increased risk of developing infection [3].In addition, this infection could develop into a pleural empyema if the obstruction  bronchoscopy performed another two months later showed complete obstruction of anterior segmental bronchus to the right upper lobe by a mass surrounded by what grossly appeared to be inflammatory tissue.Biopsies and cytology workup were all negative for malignancy.However, there was concern that the patient would be at risk for frequently developing pneumonia as a result of this endobronchial obstruction as well as the uncertain nature of the lipomatous lesion; and the patient subsequently received a right upper lobectomy via video-assisted thoracic surgery.
On gross, there was a right upper endobronchial 0.7 x 0.5 x 0.5 cm mass that appeared shiny, well circumscribed, and yellow (Figure 2); it was soft and slippery to the touch.Histology showed endobronchial submucosal mature adipose tissue consistent with endobronchial lipoma along with distal obstruction-related changes, including mild bronchiectasis, peri-bronchiolitis, accumulation of intra-alveolar foam cells, mild emphysematous changes, and rare multinucleated giant cells (Figure 3).AFB and GMS stains, completed to rule-out a mycobacterial reaction, were negative.

Discussion
Endobronchial lipomas are rare benign tumors originating from respiratory submucosa and are usually found in the first three subdivisions of the tracheobronchial tree [3].Similar to other reported cases, this patient was male and obese, and the lesion was in the right lung; however, these lipomatous endobronchial tumors are usually present in heavy smokers, and this patient had never been a smoker.While smoking and obesity seem to be prominent risk factors in developing endobronchial lipomas, it is unclear why [3]; this case does show that nonsmokers can also develop these lesions.
Additionally, while most cases had a chronic asthmatic picture (persistent cough, chest pain, dyspnea, etc), few cases have demonstrated hemoptysis, which may be from vascular impingement or post obstructive infection [5,6].These nonspecific respiratory symptoms can frequently be the first presentation and the endobronchial lesion may be missed on initial imaging study.
The clinical picture is similar to that of bronchial carcinoid, mucoepidermoid carcinoma, endobronchial hamartoma, and other lipomatous masses such as atypical lipomatous tumors or well-differentiated liposarcomas.While CT, PET, and other imaging techniques can help differentiate malignant tumors and hamartomas from lipomatous tumors, bronchoscopy biopsies is needed to differentiate lipomas from atypical lipomatous tumors or well-differentiated liposarcomas.While lipomas tend to be found endobronchially, very rarely, they can also be seen peripherally [7].Hamartomas are also often characterized by osteocartilagenous involvement [8]; while atypical lipomatous tumors and welldifferentiated tumors have atypical adipocytes and can demonstrate sclerosis [9].The latter two often are associated with heavy smoking, and ancillary immunohistochemistry or chromosomal translocation study may be helpful in diagnosing cases that are more challenging to differentiate [9].
Given the limited number of reported cases, it is not clear if the best treatment for this tumor would be electrocautery, cryotherapy, mechanical removal with forceps, or thoracostomy.While the literature supports that all of the above have been used, and can be safe without recurrence after two years of follow-up [10]; there is an instance in the literature of a patient whose forcep-resected lipoma recurred after four years [1].Further incidences should be examined and followed for longer periods to determine the best treatment option.

Figure 1 :
Figure 1: (a) Sagittal CT image showing obstructed bronchus and (b) Transverse CT image with PET overlay with lung lesion.

Figure 2 :Figure 3 :
Figure 2: Endobronchial lipomatous lesion in bronchus of the right upper lung lobe