Abstract
Bronchial granular cell tumor (GCT) is exceptionally rare, accounting for only 6%–10% of all GCT cases and may be misdiagnosed because of its nonspecific clinical and radiological features. We report a 50-year-old man with a 20-day history of intermittent cough, sputum production, chest tightness, and dyspnea. Chest computed tomography revealed a 12 × 11 mm nodule in the medial segmental bronchus of the right middle lobe, resulting in incomplete lung expansion. Bronchoscopy demonstrated a polypoid mass obstructing the bronchial lumen. Histopathological examination and immunohistochemical positivity for S100, SOX10, and CD68 confirmed bronchial GCT. The patient underwent video-assisted thoracoscopic right middle lobectomy, followed by an uneventful recovery, with no recurrence at three months. This case highlights the diagnostic challenges of bronchial GCT and supports surgical resection as the preferred treatment, particularly for lesions causing substantial bronchial obstruction.
Introduction
Granular cell tumor (GCT) is a rare neoplasm originating from the neural sheath. While it can occur in various anatomical locations, the majority of cases are found in the head and neck region. Involvement of the respiratory system is rare, and cases originating from the trachea and bronchi are particularly uncommon. Given the lack of specific clinical manifestations, bronchial GCT is often misdiagnosed. Herein, we report a case of bronchial GCT managed successfully with surgical resection, aiming to enhance clinical awareness and improve diagnostic accuracy.
Case presentation
The patient is a 50-year-old male afflicted by recurrent bouts of intermittent cough accompanied by sputum, chest tightness, and dyspnea, for the preceding 20 days. The patient's medical background is devoid of noteworthy incidents, and notably, the individual explicitly denies any history of tobacco usage or smoking behavior.
Physical examination after admission revealed coarse and slightly wheezing breath sounds in the right upper lung, while the remainder was normal. On the chest computed tomography (CT) scan, a small nodular protrusion was observed in the inner segmental bronchus of the right lung middle lobe, measuring ~12 × 11 mm with uneven enhancement (Fig. 1). The inner segmental lung tissue was incompletely expanded and appeared as a wedge-shaped dense shadow with blurred edges and increased and disorganized lung texture in the surrounding area. The image diagnosis suggested a nodular shadow in the inner segment of the right lung middle lobe bronchus, accompanied by a corresponding incomplete expansion of lung tissue, indicating a potential tumor. Subsequently, bronchoscopy was performed, revealing a polypoid mass-like neoplasm in the distal lumen of the right middle lobe bronchus, characterized by its soft texture and propensity for bleeding upon contact. It completely obstructed the lumen of the inner segment of the right middle lobe (Fig. 2). Tissues samples were obtained from the lesion site and sent for pathological examination. The pathological findings showed red blood cells, occasional lymphocytes, and neutrophils in the bronchoalveolar lavage fluid of the right middle lobe. No cancer cells were observed. On histological examination using hematoxylin–eosin (HE) staining, the tissue showed ciliated columnar epithelium covering the surface, with nests of tumor cells arranged in a patchy manner beneath the epithelium. The cells were large, with round or oval nuclei, visible nucleoli in the focal area, and abundant cytoplasm that stained pink with fine granular particles (Fig. 3a and b). Immunohistochemical results: Ckpan(+), CK7(−), TTF1(−), NapsinA(−), EMA(−), CgA(+), syn(+), CD56(+), S100(+), SOX10(+), NSE(+), CD68(+), and weakly positive for Ki67(~1% positive) and MelanA. The tumor cells were negative for CK5/6, P40, HMB45, LCA, Desmin, Myogenin, MyoD1, and DOG-1. Pathological diagnosis shows granular cell tumor.
Chest CT images. Lung windowing (a–d) and soft tissue windowing (e–h) show a small nodular protrusion in the inner segmental bronchus of the right lung middle lobe, measuring ~12 × 11 mm with uneven enhancement.
Bronchoscopy images demonstrate a soft, polypoid mass in the distal lumen of the right bronchus, which is easily touched and caused bleeding upon contact. It completely obstructs the lumen of the intermediate segment of the right middle lobe.
Hematoxylin and eosin stained sections at 200× total magnification. (a) Red blood cells, occasional lymphocytes, and neutrophils in the bronchoalveolar lavage fluid of the right middle lobe. (b–d) Pathology of tissue (b, obtained by bronchoscopy. c and d, obtained by surgery) shows the large cells, with round or oval nuclei, visible nucleoli in the focal area, and abundant cytoplasm containing fine granular particles.
The patient subsequently underwent video-assisted thoracoscopic right middle lobectomy at our hospital. Postoperative pathology revealed nests of tumor cells arranged in a patchy pattern under the microscope, with relatively large cells that had round or oval-shaped nuclei. Nucleoli were visible in the focal area, and the cytoplasm was abundant, stained with fine granular particles (Fig. 3c and d). The pathological diagnosis was granular cell tumor (right middle lobe of the lung). The bronchial margins were free of tumor involvement. No lymph nodes showed any evidence of tumor metastasis. The patient underwent a follow-up chest CT >3 months after surgery and the results indicated postoperative changes in the middle lobe of the right lung with no abnormal manifestation.
Discussion
Bronchial GCTs are thought to arise from Schwann cells. Their clinical and imaging findings are nonspecific and depend largely on the degree and duration of airway obstruction. Small lesions may appear only as endobronchial nodules, whereas progressive obstruction may produce wheeze, hemoptysis, obstructive pneumonitis, consolidation, or atelectasis [1, 2]. Because these findings overlap with those of more common respiratory disorders, diagnosis may be delayed.
Although exhibiting invasiveness and malignancy, most GCTs are benign, and diagnosis relies on pathology. Bronchoscopy is effective, and fine needle aspiration cytology (FNAC) is considered the preferred diagnostic method to distinguish between benign and malignant tumors. Bronchial GCTs typically present as pedunculated or sessile polypoid masses that protrude into the bronchial lumen without capsule. On cut surface, the tumor appears gray-white to pale yellow, with a moderate consistency and well-circumscribed margins. Observations under the microscope show that GCT generally consists of round or elliptical cells of medium size, with abundant eosinophilic granules, small nuclei, and prominent nucleoli. Typically, there is no nuclear division or necrosis [3]. The main markers used in immunohistochemical examination are positive expression of S-100 (79%–100%), NSE (98%–100%), Nestin (100%), CD56 (65%–95%), CD68 (26%–100%), and Ki-67. CgA is generally negative. An expression of Ki-67 > 10% suggest adverse prognosis [4].
The majority of bronchial GCTs are benign, with a low malignant incidence rate. However, there’s still no clear and unified diagnostic criteria for differentiation. Currently, it is believed that the characteristics of malignant bronchial GCTs include the presence of medium-sized cells with round and prominent nuclei, as well as pathological evidence such as necrosis, hemorrhage, and mitotic figures. At the same time, a series of cases have shown that the clinical features of malignant bronchial GCT are a low survival rate (5-year survival rate: 60%; 10-year survival rate: 30%), a high recurrence rate (5-year recurrence rate: 50%) and a high metastasis rate (5-year probability: 60%) [5].
Alveolar Soft Part Sarcoma (ASPS), a type of sarcoma originated from pulmonary soft tissue, has the closest resemblance to malignant GCT. The lesions of both can be observed with PAS-positive anti-amyloid enzyme particles. However, ASPS lacks strong positive expression of S-100. The expressions of Desmin, MyoD1, Myogenin, HMB45, and MelanA in GCTs are negative, as exemplified in this case, which aids in distinguishing them from metastatic carcinoma, epithelioid sarcoma, and melanoma.
Treatment should be individualized according to symptoms, tumor size, anatomic location, the suspected depth of bronchial-wall involvement, distal parenchymal changes, and the feasibility of obtaining a negative margin. Observation with serial CT and bronchoscopy may be reasonable for a small, asymptomatic, histologically benign lesion without progressive airway obstruction, particularly when procedural risk is high. Endobronchial resection preserves lung parenchyma and has shown favorable short-term outcomes in selected tumors smaller than 10 mm without local infiltration; however, it may not provide a reliable deep margin because GCT can extend through the bronchial wall, and recurrence has been reported after incomplete bronchoscopic removal [6, 7]. When endobronchial clearance is uncertain but a negative margin can be achieved, bronchoplastic or anatomic sublobar resection may preserve functioning lung. Lobectomy is more appropriate when limited resection cannot ensure complete removal or prolonged obstruction has caused distal atelectatic or inflammatory change [7, 8]. In our patient, the 12 × 11 mm tumor completely obstructed the medial segmental bronchus (B5) and was associated with incomplete expansion of the supplied parenchyma. Observation would not have relieved the obstruction, and the depth of bronchial-wall involvement and completeness of endobronchial excision could not be determined reliably before treatment. A sublobar or bronchoplastic procedure could have been considered only if an adequate bronchial margin and meaningful parenchymal preservation were achievable. On balance, video-assisted thoracoscopic surgery right middle lobectomy was selected to remove the obstructed lobe and obtain complete excision; final pathology confirmed a tumor-free bronchial margin.
Conclusion
Bronchial GCT is a rare entity that requires a high index of clinical suspicion. Surgical resection is the preferred treatment, especially for larger lesions or those causing significant obstruction. Early diagnosis and complete surgical removal are essential to prevent recurrence and ensure a favorable prognosis.
Author contributions
Yilun Wang: Writing—original draft, Conceptualization, Data curation. Yaojing Zhang: Writing—review & editing, Formal analysis, Data curation. Hongcan Shi: Writing—review & editing, Methodology, Formal analysis.
Conflicts of interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Funding
None declared.
Consent
The authors declare that written informed consent was obtained for the publication of this manuscript and accompanying images and attest that the form used to obtain consent from the patient(s) complies with the Journal requirements as outlined in the author guidelines.
