Tumors of the Lung

* Classification: 1. Benign tumors: 2. Locally malignant tumors: - Papilloma. - Fibroma. - Chondroma. 2. Locally malignant tumors: - Bronchial carcinoid 3. Malignant tumors: A. Primary M. tumors: - Bronchogenic carcinoma. - Lymphoma. - Sarcomas. B. Secondaries.

Lung cancer is currently the most frequently diagnosed major cancer in the world and the most common cause of cancer mortality worldwide. This is largely due to the carcinogenic effects of cigarette smoke. Over the coming decades, changes in smoking habits will greatly influence lung cancer incidence and mortality.

Cancer of the lung occurs most often between ages 40 and 70 years, with a peak incidence in the fifties or sixties. Only 2% of all cases appear before the age of 40.

* Etiology and Pathogenesis: 1. Tobacco Smoking. 87% of lung carcinomas occur in active smokers or those who stopped recently. There is an association between the frequency of lung cancer and the amount of daily smoking. (2) the tendency to inhale. (3) the duration of the smoking habit.

Cigar and pipe smoking also increase risk, although much more modestly than smoking cigarettes.

2. Industrial Hazards: Certain industrial exposures increase the risk of developing lung cancer. High-dose ionizing radiation is carcinogenic. There was an increased incidence of lung cancer among survivors of the Hiroshima and Nagasaki atomic bomb blasts. Exposure to asbestos.

* Classification of lung cancer: Squamous cell carcinoma (25% to 40%) Adenocarcinoma (25% to 40%) Small cell carcinoma (20% to 25%) Large cell carcinoma (10% to 15%)

* Morphology: Lung carcinomas arise most often in the hilum of the lung. These are usually squamous cell carcinoma. A small number of primary carcinomas of the lung arise in the periphery of the lung. These are usually adenocarcinomas.

Squamous cell carcinoma of the lung begins as an area of in situ cytologic dysplasia that, over an unknown interval of time, yields a small area of thickening of bronchial mucosa. With progression, this small focus, usually less than 1 cm, then assumes the appearance of an irregular mass erodes the lining epithelium.

The tumor may then follow a variety of forms The tumor may then follow a variety of forms. It may continue to fungate into the bronchial lumen to produce an intraluminal mass (fungating tumor). It can also rapidly penetrate the wall of the bronchus to infiltrate along the peri-bronchial tissue into the adjacent region of the carina or mediastinum (infiltrating tumor). In almost all patterns, the neoplastic tissue is gray-white and firm to hard. Especially when the tumors are bulky, focal areas of hemorrhage or necrosis may appear to produce yellow-white mottling and softening.

Lung carcinoma. The gray-white tumor tissue is seen infiltrating the lung substance. Histologically, this large tumor mass was identified as a squamous cell carcinoma.

Cancer lung

* Spread of cancer lung: 1. Direct spread: to pleura, pericardium…. 2. Lymphatic spread: The frequency of nodal involvement varies slightly with the histologic pattern but averages greater than 50%. 3. Hematogenous spread: to any organ. The liver (30% to 50%), brain (20%), and bone (20%) are additional favored sites of metastases.

Squamous Cell Carcinoma Squamous cell carcinoma is most commonly found in men and is closely correlated with a smoking history. Histologically, this tumor is characterized by the presence of keratinization and/or intercellular bridges. Keratinization may take the form of squamous pearls or individual cells with markedly eosinophilic dense cytoplasm . These features are prominent in the well-differentiated tumors, are easily seen but not extensive in moderately differentiated tumors, and are focally seen in poorly differentiated tumors.

Squamous cell carcinoma

Adenocarcinoma This is a malignant epithelial tumor with glandular differentiation. Adenocarcinoma is the most common type of lung cancer in women and nonsmokers. As compared to squamous cell cancers, the lesions are usually more peripherally located, and tend to be smaller. Adenocarcinomas grow more slowly than squamous cell carcinomas but tend to metastasize widely and earlier.

Small Cell Carcinoma This highly malignant tumor has a distinctive cell type. The epithelial cells are small, round, oval, and spindle-shaped. The cells grow in clusters that exhibit neither glandular nor squamous organization. Necrosis is common and often extensive. Grading is inappropriate, since all small cell carcinomas are high grade.

Small cell carcinomas have a strong relationship to cigarette smoking; only about 1% occur in nonsmokers. They occur both in major bronchi and in the periphery of the lung. They are the most aggressive of lung tumors, metastasize widely, and are virtually incurable by surgical means.

Small cell carcinoma

Large Cell Carcinoma This is an undifferentiated malignant epithelial tumor that lacks the cytologic features of small cell carcinoma and glandular or squamous differentiation. The cells typically have large nuclei.

Staging of cancer lung T: Tumor size and extension. N: (lymph nodes) T1: Tumor <3 cm T2: Tumor >3 cm T3: Tumor with involvement of chest wall T4: Tumor with invasion of mediastinum, heart, great vessels, trachea, esophagus, vertebral body, or carina or with a malignant pleural effusion. N: (lymph nodes) N0: No demonstrable metastasis to regional lymph nodes N1: Ipsilateral hilar nodal involvement N2: Metastasis to ipsilateral mediastinal lymph nodes N3: Metastasis to contralateral mediastinal or hilar lymph nodes, M: (metastasis) M0: No (known) distant metastasis M1: Distant metastasis present

* Prognosis of cancer lung: The outlook is poor for most patients with lung carcinoma.

In general, the adenocarcinoma and squamous cell patterns tend to remain localized longer and have a slightly better prognosis than do the undifferentiated cancers, which usually are advanced lesions by the time they are discovered. Surgical resection for small cell carcinoma is so ineffective that is this cancer is particularly sensitive to radiotherapy and chemotherapy.

LUNG METASTASES (SECONDARIES)

More common than the 1ry tumors. Two forms I More common than the 1ry tumors. *Two forms I. Metastases reach through pulmonary artery: From malignant melanoma, hepatoma, encocrine carcinomas, urogenital carcinoma (renal cell carcinoma and testicular tumors), sarcomas and leukaemias. N/E: multiple nodules, variable in size scattered all over the lung lobes especially at the periphery. Metastases from RCC and seminoma are large in size and spherical in shape called “cannon-ball secondaries”. M/P: like its 1ry. II. Metastases reach through lymphatics: From cancer breast, abdominal carcinomas and lymphoma.

Metastatic adenocarcinoma in the lung