Benign Tumors of Lungs.

Benign tumors of lungs

The Lung cancer surveillance program using a low dose CT scan has resulted in an increase in the detection of lung nodules/ masses. One in every 100 CT scans detects a benign lesion, only a fraction of these nodules are true benign tumors, and the majority are due to infectious granulomas. The plain chest x-ray detects one benign nodule out of 500 chest x-rays.

The previous generation of clinicians included low grade malignant tumors and also benign looking tumors with the tendency of local recurrence and distant metastasis, under the Bronchial Adenomas. Now the malignant and potentially malignant tumors are excluded from the adenoma of the lungs and naturally, the incidence of adenoma has changed.

Benign tumors of the lungs are diverse. All of these tumors, however, have a common mode of presentation, symptoms, methods of diagnosis and options for treatment modalities.

Tumors originating in other structures of the chest are excluded in this discussion.

Mode of presentation.

Incidental.  Patients are symptoms free at the time of detection of a tumor on a CT scan or plain chest x-ray. These tumors are located peripherally.

Symptomatic.  Patients' symptoms are of two categories.

Symptoms of airway obstruction. Patients complain of wheezing, hemoptysis, shortness of breath. These tumors are centrally located in the major bronchi and trachea.

Symptoms of alveoli damage. Repeated pneumonia in the location, lung abscess, chest pain. The tumors are peripherally located.

Work up.

Bronchoscopy and biopsy of lesions are all that are required to make a final diagnosis.

Treatment options.

Tumors are slow growing and often the patients are asymptomatic - waiting with follow up is generally advised.

Surgery.  Most patients are better off having the tumor removed by a limited surgery by video assisted thoracoscopic surgery.

Other modes of tumor ablations are rarely advised.

Classification and some aspects of Benign Tumors of Lungs.

Hamartomas.

Hematomas are the most common benign tumor of the lung. Hamartoma originates from the retained totipotent fetal cells in the lung. The pathological pictures are of a mixed cellular type. Normal lung tissues are mixed with growths from cartilage, fat cells, muscles and mucus glands.

10 % of patients complain of obstructive symptoms. X-ray shows a single mass with a very clear defined border. Occasionally seen as a lobulated nodule of 3cm size A popcorn calcification is a very distinct feature, but diffuse, stippled, or macular calcification may be present. The average age of patients is 40 -60 yrs; the male-female ratio is 2:1.

Bronchial Adenoma.

These benign tumors originate from the lining epithelial cells of the mucus glands of the bronchus. The tumor usually projects into the lumen of the airways. Symptoms are from airway obstruction. The pathological picture consists of mucus filled small acini lined with columnar cells.

Hemangiomas.

This is usually a single lung lesion, when lung hemangioma is a part of hemangioma of the face, the tumor behaves differently and is discussed in an earlier blog. Most patients are symptom free, when they have symptoms, they are from infection and hemoptysis. Histologically there are sheets of rounded endothelial cells lining blood filled spaces, occasional papillary cellular pattern is present.

Leiomyomas.

Leiomyomas arise from smooth muscle cells of the bronchi. All age groups of patients are involved. Female patients are specially prone to leiomyoma. The microscopic picture is bundles of spindle cells with elongated pale nuclei. Rare calcification is seen.

Lipomas.

Lipomas are seen in the major airways, as polypoidal mass projecting into the lumen usually has a morrow base but some lipomas take an hourglass appearance due to intrabronchial and extra bronchial parts. Lipomas originated from the fat cells of the bronchus or from fat cells of the connective tissue situated in between the cartilage rings. The male-female ratio is 5 :1, and the onset of symptoms is at 50 yrs. or older age. The histological picture is a fat cell mixed with some muscle cells and glands.

Lymphangiomyelomatosis.

 The origin of this tumor is the smooth muscle of lymphatics. The tumor may extend to the bronchial wall, venules, arterioles and alveolar sacs. The patients are females of childbearing age, present with shortness of breath. At times patients have persistent chylous pleural effusion and hemoptysis. Female reproductive hormones are perhaps responsible. X-ray shows lower lobe infiltrates of linear or fine nodular infiltrates with hyperinflations of the remaining lung. The diffusion capacity of CO (carbon monoxide) is reduced, so also the ventilation-perfusion ratio, and dead space of the lung is increased, and also the total lung capacity.

Pathological picture - hypertrophy of the smooth muscles of the entire lung and obstruction of all smaller airways.

Lymphangiomas. 

These tumors originate from the wall of lymph channels, tumor consists of lymph filled spaces lined by columnar or cuboidal cells and rarely of stratified squamous cells, making an appearance of a honeycomb. An occasional collection of lymphocytes is also present.

Papillomas.

The tumors are present in the larynx, trachea and main bronchus. Human papillomavirus infection may be responsible. Mixed cell papillary growths are a common pathological picture. In rare instances carcinoma in situ is present. Hoarseness of voice and cough are presenting symptoms.

Neurofibromas.

These benign tumors originate in nerve tissues of the lung, and lesions are round, oval, or lobulated. They are located outside the bronchus. Tumors compress the airways. Tumors are composed of bundles of elongated nerve fibers with palisading nuclei. The bundles are separated by fine fibers called Antoni A tissue.

Myoblasts. The tumor cells have fine granular eosinophilic cytoplasm, and cells are ovoid and polygonal. patients are young and both sexes are equally affected.

Chondromas.

These tumors are not to be confused with hamartomas. Tumor originates from the cartilage cells for the rings of major airways.

Pseudotumor. 

This is a radiological finding, not a tumor as such. When fluid accumulates in the horizontal fissure between the right upper and middle lobes of the lung, on PA chest X-ray shows a spindle shaped tumor and on the right lateral view, the mass appears as a triangle. The tumor disappears as fluid dissipates from improved congestive heart failure. For this reason, the tumor is also called a phantom tumor and a vanishing tumor.

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