Bronchoscopic Management of Endobronchial Atypical Carcinoid With Argon Plasma Coagulation and Laser: A Rare Case With Literature Review

Atypical carcinoid belongs to a spectrum of neuroendocrine tumors that can present as central airway obstruction. We treated a 58-year-old female who presented with recurrent pneumonia. Flexible bronchoscopy showed complete obstruction of the tumor in the right lower lobe. The tumor was excised by electrocautery snare followed by laser and argon plasma coagulation (APC). Endobronchial biopsy showed atypical carcinoid with lymph node metastasis. Succeeding bronchoscopic management, the patient’s symptoms improved. In our patient, bronchoscopy with laser and APC was performed to prevent tumor recurrence after resection and reduce the risk of recurrent postobstructive pneumonia. Surveillance computed tomography at six months showed no evidence of recurrence. Bronchoscopic management should be considered in poor surgical candidates or patients with metastatic disease.


Introduction
Atypical carcinoid (AC) is a rare neuroendocrine tumor that can present as an obstructing endobronchial mass [1]. Contrasted to typical carcinoid, ACs have a higher malignant potential with lower survival rates [2,3]. Localized tumors have been historically managed by surgical resection as the mainstay of treatment [2,3]. Recent literature however has shown excellent long-term outcome after first-line bronchoscopic therapy of endobronchial carcinoid tumors in a subgroup of patients [2][3][4]. Compared to surgical resection, bronchoscopic management is minimally invasive and parenchyma sparing [2,3]. We present a case of endobronchial AC managed with bronchoscopy.

Case Presentation
A 58-year-old female developed dyspnea and a productive cough. She was diagnosed with pneumonia and received antibiotics. Despite this, her symptoms worsened. Computed tomography (CT) revealed lobulated finger-like opacities with consolidation in the right lower lobe (RLL) ( Figure 1A). Flexible bronchoscopy found that the RLL was completely obstructed ( Figure 1B). Removal of the mucoid impaction revealed an endobronchial tumor originating from the RLL medial basal segment ( Figure 1C). The tumor was then excised piecemeal using an electrocautery snare and cryoprobe (Video 1). Tumor base coagulation was performed using diode laser and argon plasma coagulation (APC) for hemostasis (Video 1). All RLL branches were ultimately visualized following debulking ( Figure 1D). The mediastinal staging was then performed with endobronchial ultrasound. Fine needle aspiration biopsy confirmed a neuroendocrine neoplasm favoring primary pulmonary AC with subcarinal and right lower paratracheal lymph node metastasis (Figures 2, 3). The patient was presented to the tumor board, deciding that she was a poor surgical candidate. Following our bronchoscopic intervention, the patient's cough and dyspnea were immediately improved. She was referred to oncology and was treated with carboplatinpaclitaxel chemotherapy with concurrent fractionated radiotherapy. Surveillance CT at six months showed no evidence of recurrence.

Discussion
ACs belong to a spectrum of neuroendocrine tumors that account for 2% of all primary lung tumors [1]. ACs account for 10% of this subgroup, while the remaining are typical carcinoid, large cell carcinoma and small cell carcinoma [3,4]. The literature on endobronchial management of AC tumors largely comes from surgical series utilizing bronchoscopic resection as an adjunct with surgery [2,5]. A recent meta-analysis by Reuling et al. noted that no randomized trials to compare bronchoscopic management alone versus surgical treatment of pulmonary carcinoid tumors have been performed at present [6]. The obvious concern is the potential for tumor regrowth despite endobronchial treatment. Another concern is the development of the late recurrent disease that would be beyond curative surgery [3]. Conversely, a prospective study noted a 7.8% recurrence in the initial bronchoscopic treatment group requiring surgery without an uncompromised outcome in survival [3].
Clinically, it is difficult to discern whether there is a remnant tumor at the resection margin during the endobronchial intervention. Previous studies have reported that additional laser ablation to the tumor bed has been efficacious to prevent tumor recurrence [7][8][9]. In our case, laser and APC therapy was performed after resection. Our technique also reduces the risk of recurrent postobstructive pneumonia. Snare electrocautery and cryoprobe following debulking were preferred due to low risk for hemorrhage.
Not all patients with AC can be treated by bronchoscopy because many tumors also include extraluminal components also known as the "iceberg phenomenon." A recent study evaluating the potential prognostic factors when considering primary bronchoscopic management found that small intraluminal tumors of ≤2 cm without signs of extraluminal growth were the most suitable for endobronchial resection, while all other tumors larger than 2 cm should be referred to surgery [3,6]. Currently, there are no guidelines for preoperative mediastinal lymph node staging for endobronchial carcinoid tumors [3][4][5][6][7]. Previous studies have shown that endobronchial intervention, without lymph node dissection, did not influence survival in patients [3,4].
Central carcinoid tumors may be associated with a mucoid impaction [10]. A bronchocele, or mucoid impaction, is a common radiographic finding best characterized as tubular opacities, also known as the finger-in-glove sign [11]. Bronchoceles are most associated with benign neoplastic processes including lipomas, endobronchial hamartomas, and papillomatosis [11]. Rarely are they associated with malignancies [11].

Conclusions
AC tumors with lymph node involvement can be effectively managed with bronchoscopic resection in carefully selected patients who are poor surgical candidates. ACs can also be associated with a bronchocele, so we recommend bronchoscopy for direct visualization and to rule out malignancy. Given the rarity of this tumor, patients should be presented to the tumor board as a multidisciplinary approach is favored. Further studies comparing endobronchial tumor ablation techniques seem warranted.

Additional Information Disclosures
Human subjects: Consent was obtained or waived by all participants in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.