Bronchial Adenoma.

 

Bronchial Adenoma

PKGhatak,MD

Bronchial adenomas are mostly benign, but some adenomas have malignant potential and still, others are low grade malignant. Bronchial adenoma arises underneath the surface layer of the mid-sized bronchus of the lower lobes of the lungs. In rare cases, adenoma originates in the peripheral bronchus. An adenoma is the second most frequent primary tumor of the lung and accounts for 5 to 15 % of all primary pulmonary tumors. Adults between 30 and 40, with or without a smoking history, develop adenoma. Incidence in females is higher. It is a slow growing tumor and can be confused with cancer of the lung because of frequent and sudden onset hemoptysis or patients present with recurrent pneumonia of the same lobe of the lung indicating bronchial obstruction.

The tumors arise from the mucous gland or duct of the mucous gland. The tumor is small and the surface is covered with tiny blood vessels and appears red or fleshy pink when visualized during bronchoscopy, and manipulation of the tumor produces profuse bleeding. In 80% of cases, the adenomas grow with a wide base and grow towards the lumen and at times a filamentous adenoma may be found hanging in the lumen. Adenoma also grows towards the outer walls but less frequently.

Pathological types.

The adenomas are classified as Cylindroma and Carcinoid. Cylindromas are then subclassified as adrenocystic and mucoepidermoid adenomas.

Adenocytic adenoma arises from the cells of the mucus glands of the bronchus. This tumor behaves like a salivary gland tumor. Mucoepidermoids are essentially benign tumors located in the main bronchus and trachea. Structurally these tumors vary from cystic to solid and contain not only mucus producing cells but also other cell types.

Pulmonary carcinoid adenomas are no different from carcinoid tumors originating elsewhere. Carcinoids account for 80% of primary lung tumors. They arise from the Kulchitsky cells acquired during embryonic development. Bronchial carcinoids secrete serotonin and blood levels of serotonin remain high in the upper portion of the body. The high blood level of serotonin produces flushing of the face, increased tearing, redness of the chest wall, wheezing, fall of BP and tachycardia, and right ventricular valvular abnormalities. Bronchial carcinoid was discussed in greater detail in an earlier blog titled “Carcinoid and other neuroendocrine tumors”. Carcinoid tumors produce paraneoplastic syndrome by secreting various hormones - ACTH, ADH, Insulin like growth hormones. Occasionally, one carcinoid adenoma secretes multiple hormones. Carcinoid tumors are characterized by uniform closely packed clusters of polygonal to small cells.

Symptoms of bronchial adenoma.

The symptom begins with an unproductive cough, specially, when a patient is recumbent in bed or assumes a particular position. And the cough stops after changing position. Recurrent bouts of respiratory infections and pneumonia of the same lobe of the lung are the second most presentation. Hemoptysis is common and occurs suddenly without any warning. However, hemoptysis stops spontaneously.

Chest pain, wheezing and shortness of breath are less frequent and mostly depend on the degree of bronchial obstruction.

Behavior of bronchial adenoma.

Pathological examination of bronchial carcinoids will not differentiate benign from malignant; the biological behavior of the carcinoid tumor, in time, reveals the true nature of the tumor. Only about 4 % of carcinoids are malignant and peripherally located and are more likely to be malignant.

Adenocystic adenoma behaves as a low-grade malignant tumor, spreads locally underneath the cell surface. It is difficult to know the extension of the tumor spread pre-operatively.

The centrally located mucoepidermoid is benign.

Diagnosis.

The nature of the presenting symptoms requires a prompt bronchoscopy. The tumor location, visual identification and biopsy are attempted in all cases. But since the tumors are small, tumors may not be identified in every case.

The plain chest x-ray may not show the tumor but the secondary pulmonary changes due to the bronchial obstruction – atelectasis, pneumonia, bronchiectasis and various combination of these are detected by chest x-rays. CT scans are more sensitive and detect adenoma in larger airways, but may fail to locate the really small tumors.

PET scans may miss the adenomas because of their low level of metabolic activities.

Octreotide scan for carcinoid was discussed in an earlier blog.

Biopsy.

The tissue diagnosis of cylindroma is performed by the usual staining of slides. Immunohistological staining is generally required for carcinoid tumors.

Treatment.

All bronchial tumors are removed by surgery whenever it is possible. Often, a lobe of the lung is required to be removed because of permanent pathological changes. Radiation therapy is an appropriate modality in the treatment of adenocystic tumors.

Prognosis.

The prognosis is very favorable for cylindromas. In carcinoid tumors, continued surveillance is necessary because of the unpredictable behavior of the tumor and specially the malignant carcinoid which metastasized to the liver early.

 

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