Pulmonary Carcinoid Tumors as an Asthma Mimic: Diagnostic Challenges, Clinical Presentation, and Management Strategies

Abstract

Background: Asthma is a common chronic respiratory disease; however, some patients continue to have symptoms despite appropriate guideline-directed therapy. Pulmonary carcinoids are rare, well-differentiated neuroendocrine neoplasms that may cause cough, wheeze, dyspnea, hemoptysis, and recurrent infection through focal airway obstruction, thereby mimicking asthma. This review summarizes the pathophysiology, epidemiology, clinical presentation, diagnostic evaluation, and management of pulmonary carcinoid tumors presenting as an asthma mimic and highlights clinical features that should prompt reconsideration of an asthma diagnosis. Methods: This is a narrative, non-systematic review. A structured search and screening process was used specifically to identify the case-level literature summarized in Table 1, but this does not constitute a systematic review: only one database was searched, no protocol was registered or pre-published, and findings are synthesized narratively rather than through meta-analysis. The search strategy used combinations of the terms “pulmonary carcinoid,” “bronchial carcinoid,” “asthma mimic,” “endobronchial tumor,” “refractory asthma,” and “unilateral wheezing” to identify 14 English-language case-level reports of carcinoid tumors presenting with or mimicking asthma; seven of these are included in the present review (Table 1), while seven others were excluded (four for an irrelevant clinical scenario, two for an alternative diagnosis of adenoid cystic carcinoma, and one for carcinoid syndrome without asthma-like features in a patient with COPD). Inclusion/exclusion followed a priori eligibility criteria established prospectively, before screening began. Screening was performed by a single reviewer, with a second-pass re-screening of all records by the same reviewer to check consistency, since no second, independent screener was available; there were no discrepancies between the two passes. A PRISMA flow diagram was not produced, consistent with the narrative, non-systematic design of this review. The included case reports were assessed using four of the CARE reporting domains (demographics, work-up, treatment, outcome/follow-up) as a means of appraisal of reporting quality rather than formal risk-of-bias assessment; results of this informal appraisal are described rather than pooled. Summary: Pulmonary carcinoid tumors are usually indolent neuroendocrine neoplasms, but centrally located lesions can narrow a major airway and cause wheeze, cough, dyspnea, hemoptysis, and post-obstructive infection. Because this presentation can resemble asthma, diagnosis may be delayed despite escalating inhaled therapy or consideration of biologic treatment. Features that should raise suspicion for a focal endobronchial lesion include localized or unilateral wheeze, adult-onset or atypical symptoms, poor or incomplete response to appropriate asthma therapy, recurrent infection in the same lung segment, hemoptysis, asymmetric breath sounds, or unexpected imaging findings. Chest CT and bronchoscopy, followed by histopathology and neuroendocrine immunohistochemistry when tissue sampling is appropriate, are central to diagnosis and to distinguishing typical from atypical carcinoids. Complete surgical resection remains the preferred treatment for most localized, resectable pulmonary carcinoid tumors. Bronchoscopic/endoscopic treatments, including Nd:YAG laser photoresection, electrocautery or snare resection, cryotherapy, and rigid bronchoscopic debulking, may be considered as parenchyma-sparing approaches in carefully selected patients with strictly intraluminal typical carcinoids; available evidence is largely retrospective and direct comparative evidence against surgery remains limited. For unresectable or metastatic disease, treatment may include somatostatin analogues, peptide receptor radionuclide therapy, targeted therapy, and other individualized systemic options. Conclusion: Pulmonary carcinoid should be considered in patients with persistent or atypical asthma-like symptoms that do not respond as expected to guideline-directed therapy. Early recognition permits timely CT imaging, bronchoscopic evaluation, histopathologic confirmation, and definitive management; surgical resection remains standard for most localized resectable tumors, while selected strictly intraluminal typical carcinoids may be considered for bronchoscopic treatment.