Lung tumors with rhabdoid features, included as variants of large cell carcinoma in the 1999 World Health Organization classification of lung tumors, are rare and have an aggressive clinical course. We report 11 patients with primary lung tumors with rhabdoid features and review the literature on this uncommon tumor. We examined samples from 7 primary (6 resections, 1 biopsy) and 4 metastatic tumor samples. All specimens were stained with immunohistochemical stains for pancytokeratin (CK), cytokeratin 7 (CK7), cytokeratin (CK20), thyroid transcription factor-1 (TTF-1), and vimentin. The patients were 7 men and 4 women whose ages ranged from 35 to 70 years. Nine patients presented with respiratory symptoms, and 9 patients had a history of heavy smoking. One patient had TNM stage I tumor, 3 had stage III tumors, and 6 had stage IV tumors at presentation; tumor stage could not be determined in 1 patient. Histological examination of these tumors showed typical rhabdoid cells: large cells with abundant cytoplasm, a large eccentric nucleus with a central macronucleolus, and a rounded eosinophilic cytoplasmic inclusion that sometimes caused nuclear indentation. These cells constituted 10% to 90% of the tumor. The "parent" neoplasm was sarcomatoid carcinoma and adenocarcinoma in 4 cases each and was large cell undifferentiated carcinoma in 3 cases. Cytoplasmic staining in the rhabdoid cells was seen in 9 of 11 cases for CK, in 4 of 10 cases for CK7, and in all 11 cases for vimentin. Nuclear staining for TTF-1 in the rhabdoid cells was absent in all 11 cases, and cytoplasmic staining for CK20 was negative in the rhabdoid cells in all 10 cases studied. Of the 9 patients with available follow-up information, 8 died of disease, and 1 is alive with no evidence of disease 20 months after the initial diagnosis. We conclude that rhabdoid features can occur in a variety of lung tumors, including sarcomatoid carcinoma. Recognizing these lesions is important because of their possibly aggressive clinical course.