Research ArticlesRhabdoid Large Cell Carcinoma of Lung, With Illustrative Immunohistochemical and Molecular FindingsDettmer, Matthias MD*,†; Hench, Juergen MD*,‡; Pang, Brendan MD†,§; Willi, Niels MD*; Cathomas, Gieri MD*Author Information *Cantonal Institute of Pathology, Liestal ‡Institute of Pathology, Department of Neuropathology, University Hospital Basel, Switzerland †Department of Pathology and Laboratory Medicine, University of Pittsburgh, Pittsburgh, PA §Department of Pathology, National University of Singapore, Singapore One of the authors (M.D.) was supported by the Fondation pour la recherche Nuovo-Soldati and the Research Support Foundation. No funds from NIH, Wellcome Trust, or HHMI were received. The authors declare no conflict of interest. Reprints: Matthias Dettmer, MD, University of Pittsburgh, A719 Scaife Hall, 3550 Terrace Street, Pittsburgh, PA 15261 (e-mail: [email protected]). Received September 30, 2011 Accepted October 17, 2011 Applied Immunohistochemistry & Molecular Morphology: May 2012 - Volume 20 - Issue 3 - p 208-213 doi: 10.1097/PAI.0b013e31823d8121 Buy Metrics Abstract Large cell carcinomas with rhabdoid phenotype (LCC-RP) account for <1% of pulmonary large cell carcinomas and are associated with extremely poor prognosis. We report a case of a 64-year-old male patient who presented at an advanced stage with a LCC-RP, arising from a poorly differentiated adenocarcinoma of the lung. Ninety percent of the tumor consisted of large pleomorphic rhabdoid tumor cells that showed eosinophilic cytoplasmic inclusions and the remaining 10% showed evidence of adenomatous differentiation. Rhabdoid areas were immunohistochemically positive for pan-cytokeratin AE1/3, epithelial membrane antigen, vimentin, thyroid transcription factor-1, integrase interactor-1, and negative for desmin. Nuclear positivity was absent for Myo-D1. The parent adenocarcinoma was positive for thyroid transcription factor-1 and cytokeratins 7. Epidermal growth factor receptor mutation analysis revealed the same mutation (p.delL747-T751) in both areas, suggesting that the malignant rhabdoid phenotype represents a dedifferentiation phenomenon of the adenocarcinoma. This is the first reported case of an Exon 19 deletion in epidermal growth factor receptor of the activating type detected in a LCC-RP associated with a poorly differentiated pulmonary adenocarcinoma. © 2012 Lippincott Williams & Wilkins, Inc.