Endobronchial lipoma

ABSTRACT Endobronchial lipomas are rare benign lung tumors that can cause bronchial obstruction and parenchymal damage. While an uncommon etiology, they are often misdiagnosed due to a clinical presentation similar to obstructive pulmonary pathologies such as COPD and asthma. Upon review of English-language literature, under 50 cases of endobronchial lipomas were documented in the prior 10 years (2011-2021). There are no clear guidelines regarding the management of this particular entity, but typically interventional debulking is the treatment of choice. Here we present another unique case of endobronchial lipoma along with our diagnostic and therapeutic methodology. The patient underwent bronchoscopic debulking via a cryotherapy probe. Based on the histopathologic analysis, a diagnosis of endobronchial lipoma was made. Endobronchial lipomas must remain in any clinician’s differential when a patient presents with dyspnea. We report the unique location of this lipoma based on our literature review and the importance of investigating endobronchial lesions due to a possible diagnosis of endobronchial lipoma.


INTRODUCTION
Endobronchial lipomas are rare benign lung tumors that can cause bronchial obstruction and parenchymal damage. They can mimic chronic o b s t r u c t i v e p u l m o n a r y d i s e a s e ( C O P D ) o r asthma. 1 Diagnosis is made by imaging studies, mainly computed tomography scan (CT scan), and then confirmed by a biopsy. Early diagnosis is essential to prevent possible bronchial obstruction or further complications. Bronchoscopic resection has now become the preferred mode of treatment versus surgical intervention. 1

METHODS
A search on PubMed was conducted using the keywords "endobronchial lipoma." Only articles between 2011-2021 were considered. At the time of search under these parameters, there were 48 results. Of the 48 results, 35 articles, including case reports or any mention of a patient with endobronchial lipoma, were used. Foreign articles were used only if the full article was written in English. Articles reporting myxomas or hamartomas without specifying endobronchial lipoma were excluded. One article was used that included 4 case reports, 2 of which were reported to be endobronchial lipoma. 2 Any meta-analysis or clinicopathological reviews were also excluded from Table 1.

RESULTS
We reviewed the literature between 2011-2021. Of the 32 articles that were encountered, there were a total of 35 reports of patients with endobronchial lipoma (Table 1).
Of the reported cases, 17 cases were of the left lung bronchi, and 20 were of the right lung bronchi ( Table 2). One of the cases detailed an endobronchial lipoma at the bifurcation of the left upper and lower lobe bronchi. The majority of cases involved patients that were ≥ 60 years old (26 cases) and male (27 cases). One article did not identify the patient's gender. Most were treated with bronchoscopic resection (electrocautery, laser). There were 3 articles that did not specify their method of treatment.

CASE REPORT
We present a 70-year-old male patient who had progressive dyspnea on exertion, chest pain, and lightheadedness 2 months after bicuspid aortic valve replacement surgery. He had routine imaging studies pre-operatively. His past medical history was significant for hypertension, atrial fibrillation, obstructive sleep apnea, hyperlipidemia, chronic diverticulitis, and sigmoid abscess post colectomy.
CT scan of the chest revealed a hypodense lesion in the right middle lobe bronchus with negative Hounsfield values consistent with the macroscopic fat component ( Figure 1A). Subsequently, endobronchial ultrasound (EBUS) was indicated, where a right middle lobe mass was found with 99% obstruction ( Figure 1B).
He underwent debulking using a cryotherapy probe followed by hemostasis control with an argon plasma coagulation probe; about 50% was resected. Histopathologic examination revealed ciliated bronchial epithelial lining underneath endobronchial glands and mature adipose tissue with no cartilaginous structure ( Figure 2). Thus, the final diagnosis of endobronchial lipoma was rendered. On follow-up, no pulmonary nodules were noted.

DISCUSSION
Endobronchial lipomas are rare. They have an incidence of 0.1 to 0.5% of all lung tumors. 1,33 Though benign, it can cause bronchial obstruction and subsequent complications, such as early-onset dyspnea and wheezing. Unfortunately, their ultimate diagnosis can be easily overlooked, as providers may initially investigate the diagnosis of other more common obstructive pathologies (i.e., COPD, asthma). They usually present insidiously, most commonly in older men. Further symptoms can include dyspnea, cough, fever, chest pain, hemoptysis, and pneumonia. 3 Management options can vary among cases of endobronchial lipomas, the most common and effective treatment being bronchoscopic resection. Among cases analyzed since 2010, according to one review, seventy three percent of endobronchial lipomas were resected bronchoscopically. 1 Methods of bronchoscopic resection include cryotherapy, laser, electrosurgery, and mechanical debulking. 1,3 According to case reports by Huisman et al., 34 electrocautery can also be used as an effective treatment.
U p o n r e v i e w o f 1 0 c a s e s i n t h i s series, 3,6,7,[9][10][11]25,26,28,30 regardless of lipoma location, most of the diagnoses of endobronchial lipoma were secondary to presenting symptoms such as non-specific throat pain, shortness of breath upon exertion, and/ or cough. These symptoms showed gradual resolution when the lipoma was resected. While an incidental diagnosis of endobronchial lipomas has been made, this is rather rare; diagnosis typically only occurs after the patient presents with relevant respiratory symptoms.
Similar to the cases seen in the literature review, our patient also presented with initial symptoms of labored breathing and chest pain. Unique to our case is the specific location of the mass. While the majority of cases presented in the right main or right lower lobe bronchi (Table 2), ours was located in the right middle lobe bronchus.
O u r p a t i e n t u n d e r w e n t d e b u l k i n g a n d cauterization, similarly following the trend of the other reported bronchoscopic mass resections seen in the case review. More invasive procedures, like lobectomies, were reserved for cases in which there was irreversible parenchymal damage, suspicion of diagnosis, or if bronchoscopic resection was not    obstruction. There is a significant need to investigate endobronchial lesions as endobronchial lipoma should remain in the differential diagnosis.