Updated: Nov 13, 2008
Bronchial adenoma is a descriptive but misleading term for a diverse group of respiratory tract neoplasms that arise beneath the bronchial epithelium or in bronchial glands. They are characterized by a clinical course that is usually more benign than that of bronchogenic carcinoma. Three types make up approximately 95% of bronchial adenomas. Carcinoids (2 types of bronchial neuroendocrine tumors) account for 85% of bronchial gland tumors and 1-2% of all lung malignancies. Adenoid cystic carcinoma (cylindroma) most commonly arises in a salivary gland and accounts for 10% of bronchial adenomas. Of all bronchial gland tumors, 1-5% (and 0.1-02% of all lung tumors) are mucoepidermoid carcinoma. The common bronchial gland adenoma is the truly benign mucous gland adenoma. Additional mesodermal lesions and other lesions can arise in the tracheobronchial tree.
Laennec described a bronchial carcinoid in 1831. In 1907, Oberndorfer introduced the term karcinoide to indicate “resembles carcinoma.” In 1930, Kramer grouped bronchial carcinoids and cylindromas as bronchial adenomas because of their better prognosis and less aggressive behavior compared with bronchogenic carcinoma. Mucoepidermoid tumors were described in 1952. In 1972, Arrigoni identified a more aggressive subset of carcinoids and classified them as atypical carcinoids, as opposed to the less aggressive typical carcinoids. Bronchial carcinoids are part of a spectrum of neuroendocrine tumors (see below), of which only the first 2 are considered bronchial adenomas.
Bronchial neuroendocrine tumors, including tumor type and level of malignancy, are as follows:
Treatment is surgical, often using conservative techniques. In 1932, Bigger performed the first bronchoplastic procedure, a bronchotomy for removal of a left mainstem endobronchial lesion. In 1939, Eloesser performed a bronchotomy with simple excision and fulguration of an adenoma of a left lower lobe orifice. In 1947, Price-Thomas performed the first sleeve resection for an adenoma originating in the right mainstem bronchus.
Etiology
Bronchial carcinoids are thought to arise from Kulchitsky cells. These neuroendocrine cells, formerly classified as amine precursor uptake and decarboxylation cells, produce and store biogenic amines and peptides. Typical carcinoids originate as clusters of monotonous polyhedral cells in a fibrovascular stroma. Ultrastructurally and immunoreactively, carcinoids share characteristics with small cell neuroendocrine carcinoma of the lung.
Adenoid cystic carcinoma originates from salivary gland tissue. Occasionally, some tumor cells in this variant are of myoepithelial origin. These tumors have several other names, including cylindromas, adenoid cystic basal cell carcinomas, adenomyoepitheliomas, and pseudoadenomatous basal cell carcinomas.
Mucoepidermoid carcinomas originate from tracheal and proximal bronchi. These tumors are of squamous and intermediate elements, with intercellular bridges. They have the same microscopic appearance as mucoepidermoid carcinoma of the salivary glands, arise in glandular submucosa, and manifest as submucosal lesions.
Mucous gland adenomas (ie, bronchial cysts, papillary cystadenomas) are rare submucosal tumors arising from mucous glands and truly are benign tumors.
A related eMedicine article is Carcinoid Lung Tumors.
Symptoms develop from the growth of the tumors within the tracheobronchial tree, with consequent obstruction leading to atelectasis or pneumonia.
Adenoid cystic carcinoma behaves very similar to major and minor salivary gland tumors. An important aspect of these tumors is that they tend to spread in a submucosal plane along the perineural lymphatics, beyond the obvious endoluminal margins of the tumor. Most do not metastasize; however, total excision by tracheal resection or tracheobronchial resection is not always possible because of extensive submucosal spread, and local recurrence remains a possibility.
Tumor location
Paraneoplastic involvement
Endocrinopathies associated with bronchial carcinoids include Cushing syndrome (with increased corticotropin levels), hyperpigmentation (excess melanocyte-stimulating hormone), syndrome of inappropriate excretion of antidiuretic hormone, and hypoglycemia. In addition, bronchial carcinoids may be associated with multiple endocrine neoplasia syndrome in up to 4% of patients, the majority of whom are female.
Carcinoid syndrome is a clinical entity that includes cardiovascular, gastrointestinal, respiratory, and cutaneous manifestations. Carcinoid syndrome occurs most commonly when gastrointestinal carcinoids metastasize to the liver and less frequently when due to bronchial carcinoids. Serotonin seems to play a major role in the manifestations of carcinoid syndrome. When released into the blood stream from gastrointestinal carcinoids, serotonin is broken down in the liver. However, in the presence of liver metastasis, serotonin has a diminished opportunity to be exposed to hepatic metabolism.
Bronchial carcinoids seem to produce diminished amounts of serotonin, and carcinoid syndrome is uncommon; however, when it does occur as a result of a bronchial carcinoid, it may be unusually severe. Carcinoid syndrome can be associated with cardiac valvular fibrotic lesions. These are usually on the right side when the syndrome is due to hepatic metastases, but they may be on the left side in the presence of a right-to-left cardiac shunt or carcinoid syndrome due to a bronchial carcinoid.
Cushing syndrome occurs in less than 1% of patients with bronchial carcinoid, but it still is the second most common paraneoplastic syndrome. An occult bronchial carcinoid should be sought in a patient with Cushing syndrome and no evident adrenal or pituitary source. Cushing syndrome due to bronchial carcinoids is most often the result of peripherally located tumors, many of which may be radiographically occult. Carcinoid metastases maintain a corticotropin hypersecretory status despite resection of the primary tumor.
Up to 60% of patients have no symptoms. This is more likely if the adenoma is located peripherally as opposed to proximally. When present, symptoms are related to the presence and degree of endobronchial occlusion and the vascularity of the tumor. Hemoptysis occurs in 18%, recurrent infection or cough in 17%, dyspnea or wheezing in 2%, and carcinoid syndrome in 1%.
Physical examination generally is unrevealing, but subtle findings may provide clues. In addition, the physical examination may help in finding other confounding disease processes.
Bronchial carcinoids are thought to arise from Kulchitsky cells. These neuroendocrine cells, formerly classified as amine precursor uptake and decarboxylation cells, produce and store biogenic amines and peptides. Typical carcinoids originate as clusters of monotonous polyhedral cells in a fibrovascular stroma. Ultrastructurally and immunoreactively, carcinoids share characteristics with small cell neuroendocrine carcinoma of the lung.
Adenoid cystic carcinoma originates from salivary gland tissue. Occasionally, some tumor cells in this variant are of myoepithelial origin. These tumors have several other names, including cylindromas, adenoid cystic basal cell carcinomas, adenomyoepitheliomas, and pseudoadenomatous basal cell carcinomas.
Mucoepidermoid carcinomas originate from tracheal and proximal bronchi. These tumors are of squamous and intermediate elements, with intercellular bridges. They have the same microscopic appearance as mucoepidermoid carcinoma of the salivary glands, arise in glandular submucosa, and manifest as submucosal lesions.
Mucous gland adenomas (ie, bronchial cysts, papillary cystadenomas) are rare submucosal tumors arising from mucous glands and truly are benign tumors.
Histoplasmosis
Adenocarcinoma of the lung
Large cell lung cancer
Squamous cell lung cancer
Carcinoid
Mucoepidermoid carcinoma
Adenoid cystic carcinoma
Granuloma
Hamartoma
Metastatic cancer
Aspergillosis: This may occur in association with malignant disorders. Uncommonly, it accompanies benign carcinoid and can lead to a delay in diagnosis of the adenoma.
Recurrent lobar pneumonia: Consider primary endobronchial tumor as the etiology, especially in children.
Asthma: Asthma can be an early cause of misdiagnosis, a common error with obstructing tracheobronchial lesions.
No single investigative method is adequate to diagnose bronchial tumors in all patients, but most tumors are detectable. Laboratory, radiographic, and procedural techniques are required to locate lesions.
Carcinoids originate from bronchial epithelial stem cells and are not of neural crest origin. Grossly, they appear as soft, highly vascularized, and pink-to-purplish tumors. They are usually covered by intact epithelium, which occasionally has squamous metaplasia, and ulceration can be present. Carcinoids usually are sessile, but they can be polypoid. They may penetrate the bronchial wall and occasionally may show parenchymal or peribronchial nodal extension.
Microscopically, the cells are uniform and round-to-polygonal; however, when they are located peripherally, a spindle shape predominates. The cellular arrangement usually involves small clusters, interlacing cords, or both, separated by well-vascularized connective tissue. Nuclei are small and oval, and finely granular chromatin with abundant eosinophilic cytoplasm is observed. Typical carcinoids, or Kulchitsky cell type I neuroendocrine tumors, have less than 2 mitoses per 2 mm2 and they lack necrosis.
Atypical carcinoids, or Kulchitsky cell type II neuroendocrine tumors, have carcinoid morphology with 2-10 mitoses per 2 mm2 or necrosis. They exhibit malignant histologic features and aggressive behavior. They exhibit pleomorphism, more mitotic activity, nuclear abnormalities, prominent nucleoli with peripheral palisading, and necrosis.
Kulchitsky type III cells are thought to be the cells of origin of small cell carcinoma.
A rare, pigmented, melanocytic variety of carcinoid has been described and is differentiated from melanoma.
An oncocytic type is a rare subtype of typical lesions with mixed cellular content, including typical carcinoid cells and large eosinophilic oncocytes. True oncocytic differentiation occurs.
Adenoid cystic carcinomas are slow-growing tumors with the propensity for submucosal invasion, perineural invasion, and distant metastasis. Numerous prominent mitochondria and serous secretory granules can be observed with electron microscopy.
Tumorlets are foci of atypical hyperplastic bronchial epithelium. These lesions are more commonly seen in middle-aged or older individuals with chronic pulmonary pathology. They are usually an incidental finding in a resected specimen or are found during an autopsy.
No correlation is shown to standard tumor, node, metastases (TNM) classifications. Most typical lesions are stage 1 tumors at presentation. More than 50% of atypical lesions are at stage 2 or 3 at presentation, with bronchopulmonary or mediastinal nodal involvement noted. Intraoperative biopsies of hilar and lobar nodal tissue and tissue in the involved bronchopulmonary segment, with frozen section analysis, are required.
In the absence of distant metastases, the treatment of choice is complete removal of the primary carcinoid with maximal parenchymal preservation. This is based on the knowledge that most bronchial adenomas are only locally invasive. See Surgical Care below.
ChemotherapyAdenoid cystic tumors are radiosensitive and postoperative radiotherapy is of value.
Endoscopic resection
Bronchoscopic resection
This procedure is plagued by incomplete tumor removal, with frequent recurrence due to extraluminal tumor bulk, often with limited tumor visibility and accessibility via the bronchoscope. It also carries a high risk of hemorrhage.
Bronchoscopic resection is warranted to alleviate bronchial obstruction in patients in whom thoracotomy is prohibitive. Additionally, occasional preoperative use of this technique may allow assessment of the reversibility of distal parenchymal damage. Finally, the technique of argon-beam electrocoagulation may be very useful for bronchoscopic control of bleeding prior to definitive resection.
Neodymium:Yttrium-aluminum-garnet laser
The Nd:YAG laser reduces the risk of hemorrhage-related complications by means of photocoagulation. It is not recommended as a primary mode of tumor removal. Rarely, the Nd:YAG laser is applicable to a polypoid, easily accessible lesion on a narrow, uninvolved stalk.
Surgical resection
In the past, as many as 62% of patients with bronchial adenomas underwent lobectomy or pneumonectomy. They frequently had significant delays in their diagnosis and had complete obstruction of a bronchus with distal parenchymal destruction. Complete tumor removal, removal of all destroyed lung parenchyma, nodal dissection, and preservation of functional parenchyma are the goals of resectional therapy.Surgical procedures
Preoperative endobronchial resection may be used as part of the preparation of the patient for surgical resection.Preoperative risk assessment
Tests and evaluations other than those listed below may be appropriate as suggested by history, physical examination, and laboratory testing findings.Cardiac evaluation
Perioperative management
Monitoring and positioningChemotherapy and radiotherapy can be instituted if indicated, as discussed in Medical Care.
If the endoscopist is not prepared to deal with airway bleeding, biopsy should be deferred until the patient has been sent to an appropriate facility.
No preventive regimen has been established. Smoking cessation is always a good thing but has no specific effect on these tumors.
The overall 5-year patient survival rates for bronchial adenomas are excellent at approximately 96%. Scattered reports describe local recurrences or distant metastases following adequate resection of typical lesions.
Carcinoids
The slow growth pattern of carcinoids often prolongs the natural history of the disease process. A 5-year patient survival rate of 92% and 10-year survival rate of 88% has been reported for typical carcinoids treated with complete resection and formal mediastinal dissection. These excellent results applied to patients with both N1 and N2 disease, although those with N2 status received adjunctive radiation therapy. In atypical carcinoids, the survival rate is decreased to 60% at 5 years and 49% at 10 years.
Adenoid cystic carcinoma
After resection, the 5-year survival rate is approximately 83% and the disease-free survival rate is 60%. Patients with adenoid cystic carcinoma have an excellent prognosis because the tumor grows slowly and is radiosensitive. The best results are achieved when complete resection is accomplished; however, prolonged patient survival is possible even with incomplete resection.
Mucoepidermoid carcinoma
The 5-year survival rate is 11.1%. This tumor is known to cause intracranial metastases, even in the presence of minimal bronchial wall involvement. Chemotherapy and radiation are used mainly for palliation.
For excellent patient education resources, visit eMedicine's Procedures Center. In addition, see eMedicine's patient education article Bronchoscopy.
Failure to diagnose
The most common medicolegal hazard is failure to diagnose. Patients with bronchial adenoma may present with hemoptysis, chronic cough, recurring pneumonia, or simple chest discomfort. While radiographs may show segmental or lobar atelectasis or infiltrate, the tumor itself is rarely large enough to be visible and radiographic findings may be completely normal.
CT scanning should always be performed if the radiograph continues to show atelectasis over a period of 2-3 months.
Definitive diagnosis is made with bronchoscopy. Hemoptysis almost always prompts bronchoscopy, but the general clinician should remember that chronic cough and recurring pneumonia are also indications. No physician should be sued successfully if an honest effort is made to diagnose persisting atelectasis or recurring pneumonia, but that effort should generally include CT scanning and bronchoscopy.
Bleeding
Bronchoscopic biopsy may lead to bleeding, which can be severe and life threatening. Occasional reports describe spontaneous severe bleeding, or the tumor can bleed following biopsy. Any bleeding in the airway can be life threatening; however, this bleeding can usually be controlled using conservative measures. The availability of argon-beam electrocoagulation in the bronchoscopic suite can be beneficial.
Bleeding following bronchoscopy is the most dangerous pitfall. If the endoscopist is not prepared to deal with airway bleeding, a biopsy should be deferred until the patient has been sent to an appropriate facility.
Some surgeons believe the bronchoscopy should always be performed through a straight bronchoscope, but, with current equipment, fiberoptic bronchoscopy is safe. A straight bronchoscope permits better control of a bleeding biopsy site than a flexible bronchoscope, but the fiberoptic bronchoscope allows more complete inspection of all orifices and all segmental branches.
To successfully deal with bleeding, endotracheal intubation should be available and the operator should have the ability to intubate and to use an endotracheal tube to tamponade the bleeding tumor, or at least to block off the bronchus on the bleeding side to permit ventilation through the nonbleeding side. Rigid bronchoscopy should be available within the facility.
Failure to perform a biopsy
Because of the risk of bleeding, many clinicians have fallen into an associated pitfall, which is a failure to perform a biopsy on anything in the tracheobronchial tree that looks as if it may be a bronchial adenoma. To avoid this, perform the biopsy but be prepared to handle any hemorrhage.
The Medscape Medical Malpractice and Legal Issues Resource Center may be of interest.
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bronchial adenoma, endobronchial neuroendocrine tumor, Kulchitsky tumor, bronchial carcinoid, bronchial gland tumor, mucous gland carcinoma, mucous gland adenomas, mucoepidermoid carcinoma, adenoid cystic carcinoma, cylindromas, small cell undifferentiated carcinoma, malignant lung neoplasms, lung tumor, lung cancer, lung malignancy
Charles W Van Way III, MD, The Ralph Ringo Coffey Professor and Chairman, Department of Surgery, University of Missouri-Kansas City; Chief, Department of Surgery, Truman Medical Center
Charles W Van Way III, MD is a member of the following medical societies: American Association for Thoracic Surgery, American College of Chest Physicians, American College of Critical Care Medicine, American College of Physician Executives, American College of Surgeons, American Medical Association, American Medical Informatics Association, American Society for Clinical Nutrition, American Society for Nutritional Sciences, American Society for Parenteral and Enteral Nutrition, American Surgical Association, Association of Military Surgeons of the US, Central Surgical Association, Missouri State Medical Association, Shock Society, and Southwestern Surgical Congress
Disclosure: Sanofi-Aventis Grant/research funds Local PI
Gerald L Early, MA, MD, BA, FACS, FCCP, Associate Professor, Department of Surgery, University of Missouri-Kansas City
Gerald L Early, MA, MD, BA, FACS, FCCP is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, American College of Surgeons, American Medical Association, Society of Critical Care Medicine, and Society of Thoracic Surgeons
Disclosure: Nothing to disclose.
Michael Peterson, MD, Chief of Medicine, Vice-Chair of Medicine, University of California at San Francisco; Endowed Professor of Medicine, University of California at San Francisco-Fresno
Michael Peterson, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, and American Thoracic Society
Disclosure: Nothing to disclose.
Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.
Daniel R Ouellette, MD, FCCP, Associate Professor of Medicine, Wayne State University School of Medicine; Consulting Staff, Pulmonary Disease and Critical Care Medicine Service, Henry Ford Health System
Daniel R Ouellette, MD, FCCP is a member of the following medical societies: American College of Chest Physicians and American Thoracic Society
Disclosure: Boehringer Ingleheim Honoraria Speaking and teaching; Pfizer Honoraria Speaking and teaching
Timothy D Rice, MD, Associate Professor, Departments of Internal Medicine and Pediatrics and Adolescent Medicine, Saint Louis University School of Medicine
Timothy D Rice, MD is a member of the following medical societies: American Academy of Pediatrics and American College of Physicians
Disclosure: Nothing to disclose.
Zab Mosenifar, MD, Director, Division of Pulmonary and Critical Care Medicine, Director, Women's Guild Pulmonary Disease Institute, Executive Vice Chair, Department of Medicine, Cedars Sinai Medical Center; Professor of Medicine, David Geffen School of Medicine at UCLA
Zab Mosenifar, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, American Federation for Medical Research, and American Thoracic Society
Disclosure: Nothing to disclose.