Fact-sheet: Small cell undifferentiated bronchial carcinoma
Updated on 08/20/2025 at 11:40 PM
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Definition
High-grade anaplastic carcinoma, generally bronchogenic, composed of small ovoid cells with scant cytoplasm.
Possible association between small cell lung carcinoma and other types of lung cancer.
Characterized by distinctive biological features, response to chemotherapy or radiation therapy, and a tendency to metastasize.
Classification
T – Primary tumor
TX: Primary tumor cannot be assessed, or tumor proven by the presence of malignant cells in sputum or bronchial washings but not visualized by imaging or bronchoscopy
T0: No evidence of primary tumor
Tis: Carcinoma in situ
T1: Tumor 3 cm or less in greatest dimension, surrounded by lung or visceral pleura, without bronchoscopic evidence of invasion of the main bronchus
T1a: Tumor 2 cm or less in greatest dimension
T1b: Tumor more than 2 cm but not more than 3 cm in greatest dimension
T2: Tumor more than 3 cm but not more than 7 cm in greatest dimension or with any of the following features:
• involvement of the main bronchus 2 cm or more distal to the carina
• invasion of the visceral pleura
• association with atelectasis or obstructive pneumonitis extending to the hilar region but not involving the entire lung
T2a: Tumor more than 3 cm but not more than 5 cm
T2b: Tumor more than 5 cm but not more than 7 cm
T3: Tumor more than 7 cm or directly invading any of the following: chest wall, diaphragm, phrenic nerve, mediastinal pleura, parietal pericardium; or tumor in the main bronchus less than 2 cm from the carina but without involving it; or associated atelectasis or obstructive pneumonitis of the entire lung; or presence of a separate tumor nodule in the same lobe
T4: Tumor directly invading any of the following: mediastinum, heart, great vessels, trachea, recurrent laryngeal nerve, esophagus, vertebral body, carina; or presence of a separate tumor nodule in a different ipsilateral lobe
N – Regional lymph nodes
NX: Regional lymph nodes cannot be assessed
N0: No regional lymph node metastasis
N1: Metastasis in ipsilateral peribronchial and/or ipsilateral hilar and intrapulmonary lymph nodes
N2: Metastasis in ipsilateral mediastinal and/or subcarinal lymph nodes
N3: Metastasis in contralateral mediastinal, contralateral hilar, ipsilateral or contralateral scalene, or supraclavicular lymph nodes
M – Distant metastasis
MX: Distant metastasis cannot be assessed
M0: No distant metastasis
M1: Distant metastasis
M1a: Separate tumor nodule(s) in a contralateral lobe; tumor with pleural nodules or malignant pleural (or pericardial) effusion
M1b: Distant metastasis