Pulmonary Pathology Online
Pathology of Neuroendocrine Tumours of the Lung
Neuroendocrine tumours form a spectrum of lesions ranging from very well differentiated neuroendocrine tumours (carcinoid tumors) to poorly differentiated malignancies with endocrine features, typified by small cell carcinoma.
Neuroendocrine differentiation is defined at the morphologic level by the presence of a typical organoid growth pattern, at the ultrastructural level by the demonstration of dense-core neurosecretory granules, and at the immunohistochemical level by the presence of immunoreactivity for neuroendocrine markers such as chromogranin A and synaptophysin, or peptide hormones such as serotonin, ACTH and bombesin.
An important clinical association of these carcinomas is the production of paraneoplastic syndromes due to aberrant expression of peptide hormones , including Cushing’s syndrome and the syndrome of inappropriate secretion of antidiuretic hormone.
The tumour usually occurs in adults but younger patients are being diagnosed more often nowadays.
The most interesting observation is that that neuroendocrine tumours of lung produce exclusively the alpha subunit of human chorionic gonadotropin (hCG).
Cytogenetically, carcinoid tumors are characterized by 11q deletions.
Clinical manifestations depend on their size, location, and biologic activity.
a) Central Carcinoid Tumours are endobronchial, highly vascular and involve the main bronchus producing wheezing, cough, hemoptysis etc.
b) Peripheral Carcinoid Tumours often arise immediately beneath the pleura and are usually asymptomatic
About 12% of all carcinoids arise in the lung but less than 1% of lung tumours are carcinoids.
Surgical resection is curative in 90 to 95%.
About 10% are more aggressive exhibiting invasion or distant metastasis.
Pulmonary Neuroendocrine Tumours are divided into 4 major categories:
- Typical Carcinoid - well differentiated carcinoma
- Atypical Carcinoid - moderately differentiated carcinoma
- Small Cell Carcinoma - poorly differentiated and
- Large Cell Neuroendocrine Carcinoma - poorly differentiated .
The spectrum of neuroendocrine tumours. In: Sobin LH (ed). WHO International Histological Classification of Tumours. Histological Typing of Lung and Pleural Tumors. Springer-Verlag: Berlin, 1999, pp 7–9.
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