Carcinoid tumors outside the abdomen

Neuroendocrine tumors (NETs) are epithelial malignancies that can arise from multiple tissues. Gastrointestinal (GI) NETs are the most common; in this review of extra-abdominal carcinoid tumors, we focus our discussion on bronchial and thymic carcinoid tumors. Bronchial carcinoid tumors comprise a quarter of all NETs and less than 2% of all lung cancers. Thymic carcinoid tumors are extremely rare, accounting for 5% of thymic tumors. Both bronchial and thymic carcinoid tumors are histologically classified as either typical or atypical based on their mitotic rate (less than 2 or 2-10 mitoses per 10 high-powered fields (HPF), respectively). Both bronchial and thymic carcinoids can present with symptoms of obstruction and potentially carcinoid syndrome. The gold standard of management of bronchial and thymic carcinoid tumors is surgical resection. For patients with advanced disease, first-line systemic therapy is generally somatostatin analog monotherapy with octreotide or lanreotide. In patients with refractory disease, therapy generally involves peptide receptor radioligand therapy, everolimus, or cytotoxic chemotherapy. There are ongoing, prospective trials comparing the mainstays of systemic therapy for these patients, as well as ongoing evaluations of immune checkpoint inhibitors and multi-kinase inhibitors. Prognosis for both bronchial and thymic carcinoid tumors depends on histologic grade, local versus invasive disease, and extent of metastases. Herein we provide a summary of the pathophysiologic and clinical background, the current state of the field in diagnosis and management, and note of key ongoing prospective trials for patients with bronchial and thymic carcinoid tumors.

Automated summary

Neuroendocrine tumors (NETs) are malignant epithelial tumors that can arise from multiple tissues. The most common are gastrointestinal (GI) NETs, but we focus on bronchial and thymic carcinoid tumors in this review. Bronchial carcinoid tumors account for a quarter of all NETs and less than 2% of lung cancers, while thymic carcinoid tumors are extremely rare, representing 5% of thymic tumors. Both types of tumors can present with obstruction symptoms and potentially carcinoid syndrome. Surgical resection is the gold standard for managing bronchial and thymic carcinoid tumors. First-line systemic therapy for advanced disease typically involves somatostatin analog monotherapy with octreotide or lanreotide. Ongoing trials are comparing different systemic therapies, as well as evaluating immune checkpoint inhibitors and multi-kinase inhibitors. Prognosis depends on histologic grade, local versus invasive disease, and extent of metastases. This article provides a summary of the pathophysiologic and clinical background, current diagnosis and management, and ongoing trials for bronchial and thymic carcinoid tumors.