Lung Carcinoid Tumors

Excerpt

Carcinoid tumors are rare malignant neuroendocrine epithelial tumors that can develop at various sites in the body, including the gastrointestinal tract, lungs, ovaries, adrenal glands, and thyroid. Among all carcinoid tumors, those arising in the lungs account for approximately 25% of cases, making them the second most common site. However, pulmonary carcinoids account for less than 2% of all lung cancers.

Pulmonary carcinoids can be classified into 2 subcategories: typical and atypical carcinoids, with the latter, comprising only 10% to 15% of cases. Typical carcinoids are considered low-grade neuroendocrine tumors, while atypical carcinoids are classified as intermediate-grade. The grading criteria for these tumors are defined by the World Health Organization and will be reviewed in the histopathology section of this activity.

Approximately 80% of pulmonary carcinoids are located centrally within the lung, while 20% are in peripheral regions. All bronchial carcinoids are malignant and have the potential to metastasize. Unlike many other lung cancers, carcinoids are not associated with smoking. These tumors are typically small and tend to occur in central locations. Lymph node involvement is observed in less than 10% of cases, and carcinoid syndrome, a collection of symptoms caused by certain chemicals released by the tumor, is rare, occurring in less than 3% of cases.