Abstract
Pleomorphic adenoma (PA) is the most common benign histological form of salivary gland tumors, particularly in the parotid gland, primarily affecting women between the ages of 40 and 60. However, its occurrence in the trachea is very rare. This article reports the case of a 48-year-old woman presenting with progressive dyspnea and weight loss, initially suspected of having a pulmonary embolism. A chest CT scan revealed a nearly circumferential tracheal lesion with 2 nodules partially obstructing the tracheal lumen. Histological analysis confirmed the presence of a pleomorphic adenoma of the “salivary gland” type. Although rare, tracheal pleomorphic adenoma should be considered in the differential diagnosis of tracheal tumors. MRI is the preferred examination for detecting tumors in the parotid gland region, offering excellent tissue differentiation. Surgery remains the treatment of choice to prevent recurrence.
Keywords: Pleomorphic adenoma, trachea, CT scan
Introduction
Pleomorphic adenoma (PA), previously known as a mixed tumor, is the most common benign histological form of tumors in the parotid gland. It primarily affects women between the ages of 40 and 60, although this type of tumor can occur at any age [1,2].
Although pleomorphic adenoma is the most common type of parotid gland tumor, its occurrence in the trachea is very rare [3]. We report the case of a pleomorphic adenoma in a woman who experienced dyspnea and was initially suspected of having a pulmonary embolism.
Case report
A 48-year-old woman presented to the emergency department with progressive upper dyspnea and weight loss. She had a history of treated tuberculosis. Given her clinical presentation, pulmonary embolism was initially suspected. A chest CT scan (Fig. 1) was performed, which did not show evidence of a pulmonary embolism but revealed a nearly circumferential tracheal lesion with 2 nodules partially obstructing the tracheal lumen. The scan also indicated involvement of the anterior esophageal wall and close proximity to vascular structures.
Fig. 1.
Thoracic CT angiography in mediastinal window in axial (A), coronal (B), and sagittal (C) views showing a right paratracheal process (
) with 2 intratracheal buds (
) reducing the lumen.
A bronchoscopy was performed under general anesthesia using intravenous propofol. After induction, the patient was intubated with a rigid bronchoscope (Karl-Storz, Tuttlingen, Germany). An EVIS BF 1T260 flexible bronchoscope (Olympus, Tokyo, Japan) was then introduced through the bronchoscope tube, and the tumor was inspected. The tumor was located in the middle part of the trachea, 3 cm from the carina, had a smooth surface, and measured approximately 1.5 cm in diameter, causing near-total obstruction of the lumen.
APC was applied to the base, and a biopsy was performed by retrieving 2 fragments of the tumor. There were no procedure-related complications.
Histology indicated a “salivary gland” type tumor with epithelial, myoepithelial, and mesenchymal components. The myoepithelial component consisted of clear cells with nuclei arranged in clusters. The mesenchymal component was predominantly myxoid. (Fig. 2) Immunohistochemical study showed epithelial cells expressing CK, CK7, and CK5/6. Anti-A and anti-P63 antibodies were expressed by the myoepithelial cells.
Fig. 2.
Microscopic examination showing a benign tumor proliferation composed of epithelial cells arranged in sheets or tubular structures, within a myxoid background, without architectural disorganization, nuclear atypia, or mitoses. (Hematoxylin and eosin staining, original magnification x200).
Discussion
Pleomorphic adenoma is the most common tumor of the salivary glands, rarely appearing in the lungs and typically originating from the tracheal and bronchial seromucous glands [4]. The exact incidence has not been determined. Patients diagnosed with pleomorphic adenoma are generally between 35 and 74 years old, with no age or sex predilection [3]. Tumors are usually detected through imaging examinations due to the lack of specific symptoms and signs associated with this condition [5]. Although chest X-rays do not always reveal the tumors, thoracic CT scans are essential for diagnosis [5].
MRI is now the preferred examination for detecting a tumor in the parotid gland region [6]. It provides excellent spatial resolution and very good tissue differentiation. It allows for confirmation or exclusion of the need for a parotidectomy, while also helping to determine the optimal timing for the procedure [7].
Pleomorphic adenoma generally presents as a tumor with often lobulated contours when large, but with regular boundaries. On T1-weighted images, it appears hypointense, while it shows intense hyperintensity on T2-weighted images in its typical form. In some cases, the T2 hyperintensity may be heterogeneous, with areas of lower signal corresponding, according to histopathological examination, to regions with higher cellularity. After gadolinium injection, this tumor usually exhibits moderate peripheral enhancement. Central 'contrast uptake' may also be observed when histopathological examination reveals invaginations of the peripheral fibrous capsule [7].
In diffusion imaging, pleomorphic adenoma shows a high ADC (Apparent Diffusion Coefficient) greater than 1, and in dynamic imaging, it exhibits gradual enhancement with minimal washout [8].
The most complex differential diagnosis of pleomorphic adenoma is adenoid cystic carcinoma, where the clusters of tumor cells are clearly distinct from the stroma [9]. As an aggressive malignant tumor, adenoid cystic carcinoma is often associated with invasion of surrounding tissues, including perineural invasion [3].
Radiotherapy is used alongside surgical resection for inoperable tumors or for symptom palliation, with limited data available [10]. Postoperative radiotherapy of 60 Gy in 5 fractions per week over 6 weeks, or an equivalent dose of neutron therapy, can convert incomplete resections to complete ones. This treatment effectively targets residual cancer cells in the tumor bed and regional lymph nodes for both squamous and adenoid cystic carcinomas. For macroscopically residual carcinomas, the dose should be increased to 68-70 Gy over 6.8 to 7 weeks. Though data is scarce, doses exceeding 60 Gy, preferably 70 Gy in 35 fractions over 7 weeks, are suggested for effective local control of inoperable cancers [11].
Conclusion
Tracheal pleomorphic adenoma, although very rare, should be considered in the differential diagnosis of tracheal tumors. Surgery remains the best therapeutic option to prevent recurrence of the adenoma.
Author contributions
EK: Contributed to conception and design; Contributed to analysis; Drafted the manuscript; Gave final approval; Agrees to be accountable for all aspects of work ensuring integrity and accuracy.
SL: Contributed to conception and design; Contributed to analysis; Agrees to be accountable for all aspects of work ensuring integrity and accuracy.
KS: Critically revised the manuscript; Gave final approval; Agrees to be accountable for all aspects of work ensuring integrity and accuracy.
SMR: Contributed to conception and design; Contributed to analysis; Agrees to be accountable for all aspects of work ensuring integrity and accuracy
YO,RL, and SA: critically revised the manuscript; Gave final approval; Agrees to be accountable for all aspects of work ensuring integrity and accuracy.
Patient consent
Written informed consent was obtained from a legally authorized representative for anonymized patient information to be published in this article
Footnotes
Guarantor of submission: The corresponding author is the guarantor of submission.
Competing Interests: The authors declare no conflicts of interest.
Acknowledgments: I would like to express my gratitude to my professors and all the colleagues who participated in the completion of this work. This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
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