Bronchial Carcinoid Tumor

Bronchial carcinoid is a low-grade neuroendocrine tumor arising from Kulchitsky cells in the bronchial mucosa, and USMLE Step 1 tests it mostly through recognition questions. It sits in the same neuroendocrine family as SCLC but behaves very differently — slow-growing, central location, and rarely fatal if caught early. Expect vignettes featuring a young non-smoker with hemoptysis, recurrent pneumonia, or an endobronchial mass on imaging, requiring you to identify the tumor type and what it secretes. The histology is the classic neuroendocrine pattern — nests of uniform cells with salt-and-pepper chromatin — and immunostaining is positive for chromogranin and synaptophysin.

The trickiest angle Step 1 exploits is carcinoid syndrome. Students know carcinoid syndrome from GI carcinoids and assume it only appears after liver metastases (because hepatic metabolism normally neutralizes serotonin). But bronchial carcinoids drain into pulmonary veins, not the portal system — so serotonin hits the systemic circulation directly, meaning carcinoid syndrome (flushing, diarrhea, wheezing, right-sided heart lesions) can occur without any liver involvement. This is a high-yield distinction that frequently catches students off guard.

The second trap is assuming these tumors are benign. They are not — bronchial carcinoids are classified as low-grade malignancies with real metastatic potential, especially the atypical subtype. They're much better behaved than SCLC, but calling them 'benign' is wrong and could cost you a management question on USMLE Step 1. Surgical resection is the treatment of choice; somatostatin analogs (octreotide) control hormone-related symptoms when resection isn't curative.