Pulmonary large cell neuroendocrine carcinoma demonstrates high proliferative activity.

BACKGROUND: In 1999, the World Health Organization classified large cell neuroendocrine carcinoma as a variant of large cell carcinoma and this has been categorized as lying between atypical carcinoid and small cell lung carcinoma in terms of clinical aggressiveness.
METHODS: We analyzed the proliferative activity of stage 1 large cell neuroendocrine carcinoma derived from patients with primary lung cancer who underwent surgical resection and compared the results with stage 1 classic large cell carcinoma cases. The mitotic rate was counted in ten high-power fields of light microscope. Immunohistochemical staining using anti-Ki-67 antibody was performed. The Ki-67 labeling index, expressed as a percentage of positive cells, was determined by light microscopy with random counting of at least 1000 tumor nuclei. The expression of P53 and Bcl-2 was examined and compared.
RESULTS: The mitotic rate of large cell neuroendocrine carcinoma cases was significantly higher than that of classic large cell carcinoma cases. The Ki-67 labeling index of stage 1 large cell neuroendocrine carcinoma cases was significantly higher than that of stage 1 classic large cell carcinoma cases. Immunohistochemical expression of P53 in large cell neuroendocrine carcinoma and classic large cell carcinoma was comparable. However, large cell neuroendocrine carcinoma exhibited a significantly higher expression of Bcl-2 than classic large cell carcinoma. The disease specific disease-free survival for patients with stage 1 large cell neuroendocrine carcinoma was significantly lower than that for patients with stage 1 classic large cell carcinoma.
CONCLUSIONS: Large cell neuroendocrine carcinoma appears to be more clinically aggressive than classic large cell carcinoma with these findings indicating that large cell neuroendocrine carcinoma has a higher level of proliferative activity than classic large cell carcinoma.