Original ArticlesPrimary Giant Cell Tumors of the Lung A Clinicopathologic and Immunohistochemical Study of 3 CasesOramas, Diana M. MD; Moran, Cesar A. MDAuthor Information Department of Pathology at the University of Texas, MD Anderson Cancer Center, Houston, TX Conflicts of Interest and Source of Funding: The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article. Correspondence: Cesar A. Moran, MD, Department of Pathology at the University of Texas, MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030 (e-mail: [email protected]). The American Journal of Surgical Pathology: August 2021 - Volume 45 - Issue 8 - p 1151-1154 doi: 10.1097/PAS.0000000000001686 Buy Metrics Abstract Three cases of primary giant cell tumors of the lung akin to those described in the soft tissues are presented. The patients are 3 men between the ages of 43 and 54 years who presented with nonspecific symptoms of cough, chest pain, and shortness of breath. None of the patients had any prior history of malignancy anywhere else. Diagnostic imaging disclosed the presence of an intrapulmonary mass. All the patients underwent lobectomy. Grossly, the tumors were described as solid, slightly hemorrhagic, and measuring between 1.8 and 2.4 cm in greatest diameter. Histologically, the tumors were characterized by a dual population of multinucleated giant cells admixed with a mononuclear proliferation. Nuclear atypia was mild to moderate, and mitotic activity varied but was under 5 mitotic figures per 10 high power fields. Immunohistochemical stains showed positive staining for vimentin, CD68, and cathepsin K, whereas the tumors were negative for keratin, TTF-1, p40, S-100 protein, and SABT-2. Clinical follow-up was obtained in 2 patients who have remained alive and without evidence of recurrence or metastasis up to 12 months after surgery. One patient was lost to follow-up. The current neoplasms represent a tumor that to the best of our knowledge has not been reported as a primary neoplasm of the lung. The cases herein described represent an unusual occurrence and should be maintained in the differential diagnosis of primary pulmonary tumors rich in multinucleated giant cells. Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.