Pleomorphic adenoma of the trachea.

Abstract

Primary pleomorphic adenoma of the trachea is rare, as only 33 cases have been previously reported worldwide since 1922. We describe a new case of primary tracheal pleomorphic adenoma that was discovered incidentally in a 78-year-old man. The tumor was excised, and the patient recovered without complication. Salivary gland tumors of the trachea should be considered in the differential diagnosis of tracheal lesions; the diagnosis is confirmed by pathologic evaluation. Patients are adequately treated with sleeve resection and primary anastomosis whenever possible.

Introduction

Mixed salivary gland tumors are uncommon, occurring in approximately 3 to 4 persons per 100,000 population worldwide. (1) Pleomorphic adenoma is the most common subtype, accounting for approximately half of the primary mixed tumors in the major salivary glands. (1) Pleomorphic adenomas have been documented in the tongue, retromolar trigone, lips, and trachea. (2)

The reported annual incidence of primary tracheal tumors is 0.2 per 100,000 population worldwide. (2) Such tumors are responsible for less than 0.1% of all cancer deaths per year. (2) The most common primary tracheal tumors are squamous cell carcinoma and adenoid cystic carcinoma; among the others are a variety of salivary gland tumors, including pleomorphic adenoma and mucoepidermoid carcinoma. (2)

Since 1922, only 33 cases of primary tracheal pleomorphic adenoma have been previously reported worldwide in the otolaryngology and thoracic medicine literature. (3) In this article, we describe the 34th such case, and we review the histopathologic characteristics of this rare tumor.

Case report

A 78-year-old white man was referred to our otolaryngology clinic for evaluation of a tracheal mass. The mass had been discovered incidentally on computed tomography (CT) that had been obtained during a work-up for chronic neck pain. The patient denied any shortness of breath, hoarseness, or dysphagia. He had a significant medical and surgical history, including kidney stones, diet-controlled diabetes mellitus, bladder cancer diagnosed 10 years earlier and treated by total cystectomy, and cervical arthritic degenerative joint disease that required intermittent nerve block injections. His medications included ipratropium and albuterol inhalers for chronic obstructive pulmonary disease. His social history was significant for 47 pack-years of smoking, but he denied alcohol consumption.

On physical examination, the patient was afebrile. He exhibited no tachypnea, signs of respiratory distress, or audible stridor. Findings on fiberoptic laryngoscopy were normal, including bilateral vocal fold mobility. Bronchoscopy revealed that a large (2-cm) polypoid lesion had originated on the anterior tracheal wall at the second tracheal ring. No cervical lymphadenopathy was found on palpation of the neck, and findings on the remainder of the head and neck examination were unremarkable.'

New axial and sagittal CTs demonstrated a 2 x 1.2 x 2.2-cm anterior, intraluminal, heterogeneously enhancing tracheal mass at the level of the clavicle (figure 1). CT was also suggestive of central necrosis within the mass, but no significant lymphadenopathy or bony destruction of the clavicular heads was seen. CT of the thorax and whole-body positron-emission tomography were negative for metastatic lesions.

A tracheal resection with a primary end-to-end anastomosis was performed. On microscopic examination, the tumor was found to be adjacent to the tracheal cartilage (figure 2,A). Ductal structures were randomly scattered within a mesenchymal stromal component located between and around the epithelial elements. The ductal structures had large and distinct lumens as well as small, isolated, and poorly defined lumens. The lumens were lined with cuboidal and columnar epithelium with an outer layer of spindle-type and clear cells. The stroma was mainly dense and hyalinized, with focal areas of myxoid differentiation (figure 2, B). The tumor was identified as a primary pleomorphic adenoma.

The patient underwent yearly follow-up imaging, and 4 years after surgical resection he remained asymptomatic.

Discussion

Grossly, pleomorphic adenomas are round or ovoid masses that are well demarcated and exhibit varying degrees of encapsulation. The intact surface is gray-white, and the cut surface is solid with partially translucent areas that represent the histologic variations. The tumors are composed of cells that demonstrate both epithelial and mesenchymal differentiation. The epithelial component consists of ductal and nonductal cells that can be spindle-shaped, squamous, stellate, plasmacytoid, oncocytoid, cuboidal, or clear. The mesenchymal component consists of varying degrees of myxoid, hyaline, cartilaginous, and osseous differentiation; the proportion of each of these elements varies widely from case to case. Immunohistochemically, the ductal component may stain positive for keratin, epithelial membrane antigen, and carcinoembryonic antigen. The spindlecell component is positive for keratin, smooth-muscle actin, and myosin. The cartilaginous areas are positive for S-100 protein.

Fine-needle aspiration biopsy may be useful in identifying benign epithelial cells in a blue myxoid matrix background. However, given that the pathology of pleomorphic adenoma is characteristic for a number of morphologic features, a diagnosis based on fine-needle aspiration biopsy and small incisional biopsies may be extremely difficult to establish because of the tumor's widely diverse morphology and the characteristic heterogeneity between and within tumor types.

Pleomorphic adenoma of the trachea, like adenoid cystic carcinoma and mucoepidermoid carcinoma, has a less aggressive clinical course than does squamous cell carcinoma. The indolent course of the disease and its confusing presentation pose a diagnostic challenge. Most patients have a history of slowly progressive dyspnea. Given that most of these intratracheal lesions are either subglottic or intrathoracic, expiratory or biphasic stridor maymimic non-neoplastic syndromes, including asthma and bronchitis. In fact, Heifetz et al reported that 6 of 19 patients (31.6%) with pleomorphic adenoma of the trachea were initially misdiagnosed with asthma. (4) Other, less common presenting signs and symptoms include hemoptysis and chronic cough, but they may not manifest until the lumen becomes at least 75% obstructed. (5) As a result, tracheal pleomorphic adenoma is often not discovered until further diagnostic tests (i.e., imaging and bronchoscopy with biopsy) are performed and the intraluminal tracheal mass is detected.

[FIGURE 1 OMITTED]

The literature lacks formal investigations on the management and long-term follow-up of patients with tracheal pleomorphic adenoma. Without evidence-based guidance, most surgeons treat pleomorphic adenomas of the trachea as they treat tumors of the major salivary glands. The primary therapeutic modality is complete excision of the tumor via tracheal resection. With regard to surgery on major salivary glands, we know that keeping the capsule intact and resecting a margin of normal tissue reduces the 10-year recurrence rate to approximately 2%. (6) To the best of our knowledge, no case of recurrent tracheal pleomorphic adenoma has been reported following complete excision.

[FIGURE 2 OMITTED]

As is the case with the treatment of tumors of the major salivary glands, alternative but less effective treatment modalities are available for primary tracheal pleomorphic adenomas in the event that surgery fails. Neutron radiotherapy, which is known to be superior to conventional radiotherapy in treating salivary gland tumors, is reserved for patients with residual disease after surgical resection and for patients with recurrent pleomorphic adenoma. (7) Chemotherapy, which is used for palliative pain control in carcinoma of the salivary glands, has no therapeutic role in pleomorphic adenoma. (8)

References

(1.) Speight PM, Barrett AW. Salivary gland tumours. Oral Dis 2002; 8(5):229-40.

(2.) Azar T, Abdul-Karim FW, Tucker HM. Adenoid cystic carcinoma of the trachea. Laryngoscope 1998;108(9): 1297-1300.

(3.) Peretti G, Piazza C, Berlucchi M, et al. Pleomorphic adenoma: A case treated by laryngotracheal resection and reconstruction [in Italian]. Acta Otorhinolaryngol Ital 2000;20(1):54-61.

(4.) Heifetz SA, Collins B, Matt BH. Pleomorphic adenoma (benign mixed tumor) of the trachea. Pediatr Pathol 1992;12(4):563-74.

(5.) Paik HC, Lira SH, Lee DY, Paik SY. Pleomorphic adenoma of the trachea--a case report. Yonsei Med J 1996;37(1):81-5.

(6.) Webb AJ, Eveson JW. Pleomorphic adenomas of the major salivary glands: A study of the capsular form in relation to surgical management. Clin Otolaryngol Allied Sci 2001;26(2):134-42.

(7.) Douglas JG, Einck J, Austin-Seymour M, et al. Neutron radiotherapy for recurrent pleomorphic adenomas o f major salivary glands. Head Neck 2001;23(12):1037-42.

(8.) Chou C, Zhu G, Luo M, Xue G. Carcinoma of the minor salivary glands: Results of surgery and combined therapy. J Oral Maxillofac Surg 1996;54(4):448-53.

Michael J. Rodriguez, MD; Giovana R. Thomas, MD; Uzma Farooq, MD

From the Department of Otolaryngology-Head and Neck Surgery (Dr. Rodriguez and Dr. Thomas) and the Department of Pathology (Dr. Farooq), University of Miami Miller School of Medicine.

Corresponding author: Giovana R. Thomas, MD, Department of Otolaryngology-Head and Neck Surgery, University of Miami Miller School of Medicine, 1611 NW 12th Ave., ACC East, Suite 314, Miami, FL 33136. Phone: [phone]; fax: [phone]; e-mail: [e-mail]