A 22-year-old woman presented with intermittent blood-tinged sputum for about 3 years. She reported experiencing exertional dyspnoea and had no history of chronic disease, family history or smoking. On physical examination, mild coarse breathing sounds and wheezing on the upper sternum were auscultated. Lab results were non-specific.

Chest CT scan (figure 1A,B) revealed a heterogeneous enhancing endotracheal mass of approximately 1.9 cm at mid-trachea extending to the boundary of the right tracheal wall or through the tracheal wall but not invading adjacent structures. The bronchoscopy showed a tracheal mass characterised by a lobulated surface with hypervascularity (figure 1C). 2-Deoxy-2-[18F]-fluorodeoxyglucose (FDG) positron emission tomography (PET)-CT demonstrated mild to moderate uptake increase of FDG (figure 1D) and no definitive invasion to the neighbouring structures was observed on images (figure 1E). The tracheal mass was resected with a sufficient resection margin via uniportal video-assisted thoracic surgery and was reconstructed by end-to-end anastomosis.

(A, B) Images on contrast-enhanced chest CT showing a 1.9×1 cm endotracheal mass with heterogeneous enhancement at mid-trachea (yellow arrow). (C) Initial diagnostic flexible fibreoptic bronchoscopic image showing tracheal mass possessing lobulated surface with hypervascularity. (D) 2-Deoxy-2-[18F]-fluorodeoxyglucose (FDG) positron emission tomography (PET)-CT demonstrates a 1.9 cm endotracheal mass at mid-trachea with increased FDG uptake (yellow arrow). (E) T1 enhancement MRI showing endotracheal mass without any invasion to the adjacent structures (yellow arrow). (F) Postoperative bronchoscopy 10 months after the resection. There is no evidence of recurrence; tracheal patency is well preserved. (G) Follow-up chest CT and PET/CT showing a marked improvement of the tracheal acinic cell carcinoma (yellow arrow). (H) The tumour cells, which resemble normal acinar cells, display eccentric nuclei and abundant finely vacuolated to basophilic granular cytoplasm (left, H&E stain, original magnification, ×200). The tumour cells express cytokeratin (right, IHC, original magnification, ×400). (I) Immunohistochemistry results of acinic cell carcinoma. The tumour cells express DOG-1 (left), and SOX-10 (right) (IHC, original magnification, ×400).

Histological examination revealed a tumour composed of cells with basophilic granular cytoplasm and others with finely vacuolated cytoplasm. Immunohistochemical staining for CK, DOG-1 and SOX-10 confirmed the diagnosis of tracheal acinic cell carcinoma (ACC) (figure 1H,I).1 The resection margin was negative, and our patient underwent frequent follow-up without any adjuvant therapy. After 10 months, bronchoscopy and PET-CT imaging substantiated the absence of any recurrence and until now, there has been no reemergence for 2 years (figure 1F,G).

Primary tracheal ACC is extremely uncommon and typically presents in the form of an endobronchial mass that originates from the submucosal glands of the trachea.1 Until now, there is no defined staging classification for tracheal tumours that predicts recurrence or survival. On the basis of a frequently quoted staging classification for primary tracheal tumours, our patient was treated as early-stage or localised disease.2 Furthermore, histopathology revealed no reported risk factors for recurrence of ACCs of various salivary glands,3 of which the histopathological features are extremely similar to those of tracheal ACC.1 Thus, the patient received regular follow-ups without any adjuvant therapy. Meanwhile, reported cases of tracheal ACC rarely documented recurrences following tumour excision.1 4 However, considering the fact that our patient is the youngest ever reported and taking into account the documented risk of recurrence in ACCs of various salivary origin,4 the patient is undergoing vigilant thoracic image surveillance with bronchoscopy with the interval of 3–6 months.

Here, we report a very rare manifestation of ACC in the central airway. To the best of our knowledge, there have been only seven reported cases of tracheal ACC since 1982. The average age was approximately 50 years old and our patient was 22 years old being the youngest patient ever reported.1 4

Consent obtained directly from patient(s).