Large cell undifferentiated carcinoma of the lung

High-magnification photomicrograph showing large cell undifferentiated carcinoma of the lung. The tumor cells have vesicular nuclei, prominent nucleoli, and abundant eosinophilic cytoplasm. The cells are arranged in sheets without distinct architectural features. Tumor cells did not express TTF-1 (adenocarcinoma marker) or p40 (squamous marker) by immunohistochemistry. This indicated the null phenotype of large cell carcinoma.