Expression of Tyrosine Kinase Receptors in Lung Carcinoids

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Objectives: Typical lung carcinoids are usually relatively benign tumors, but distant metastases are seen in up to 12% of the patients. In contrast, atypical carcinoids are more aggressive tumors, displaying metastases in up to 70%. The current treatment of metastatic lung carcinoids is discouraging. New therapies, such as inhibitors of the tyrosine kinase receptor family c-kit, platelet-derived growth factor receptors (PDGFR) α and β and epidermal growth factor receptor (EGFR) have shown promising results in other malignancies and might be of value in malignant lung carcinoids. Patients and Methods: Tumor tissue from 51 patients with typical lung carcinoids were immunostained with polyclonal antibodies against c-kit, PDGFRα, PDGFRβ and EGFR. Of the 24 patients who had metastatic disease, 17 had distant metastases. Fifteen of the patients had died from their disease. Results: Twelve of the tumors stained positive for c-kit, 44 expressed PDGFRα, 30 showed positive immunoreactivity for PDGFRβ and 26 were EGFR immunoreactive. Among the 17 patients with distant metastases, 5 tumors expressed c-kit, 12 were PDGFRα immunoreactive, 9 stained positive for PDGFRβ, and 7 showed positive immunoreactivity for EGFR. There was no correlation to distant metastases or survival for c-kit, PDGFRβ or EGFR. Conclusions: Tyrosine kinase receptors such as c-kit, PDGFRα, PDGFRβ and EGFR are expressed in a significant number of patients with metastatic lung carcinoids. Treatment with inhibitors of the tyrosine kinase receptors expressed may be considered.