en Pathology Pathology case report case report <span style="font-size:12px;"><span style="font-family:times new roman;"><span style="color:#0000FF;"><strong><em>Background</em></strong><em>:</em></span> Metastatic carcinomas to the upper jaw region are very rare and unfortunately occur in advanced stages of malignancies. Pancoast tumor is a challenging subset of lung carcinoma commonly followed by distant metastasis. Since the metastatic lesion of our patient was very huge and unusual, we decided to report the case.<br> <span style="color:#0000FF;"><strong><em>Case Presentation:</em></strong></span> Our patient was a middle-aged heavy smoker male with a history of unresectable pancoast tumor. He was referred to the dental clinic with an expanded maxillary metastasis involving the bone and sinus region as well as oral soft tissues. To confirm the primary site of his malignancy, immunohistochemical staining was performed.<br> <span style="color:#0000FF;"><strong><em>Conclusion</em></strong><em>:</em> </span>Distant metastases of a pancoast tumor are more frequent when the primary tumor is unoperable and bone involvement is one of the early manifestations of disease.</span></span> metastatic carcinoma, Pancoast tumor, gingival metastasis, immunohistochemical staining. 351 355 http://caspjim.com/browse.php?a_code=A-10-222-3&slc_lang=en&sid=1 Ramin Forooghi raminomfs99@yahoo.com 100319475328460018122 100319475328460018122 No Oral Health Research Center, Health Research Institute, Babol University of Medical Sciences, Babol, Iran Mohammad Ranaee drm.ranaee@yahoo.com 100319475328460018123 100319475328460018123 No Cellular and Molecular Biology Research Center, Health Research Institute, Babol University of Medical Sciences, Babol, Iran Fatima Bijani fatimahb56@gmail.com 100319475328460018124 100319475328460018124 No Department of Oral pathology , Dentistry Faculty, Babol University of Medical Sciences, Babol, Iran Safoura Seifi sf_seify@yahoo.com 100319475328460018125 100319475328460018125 Yes Oral Health Research Center, Institute of Health, Babol University of Medical Sciences, Babol, Iran Daryoosh Moslemi 100319475328460018126 100319475328460018126 No Cancer Research Center, Health Research Institute, Babol University of Medical Sciences, babol, Iran Mohammadreza Mohammadi mohammadrezamohammadi08@gmail.com 100319475328460018127 100319475328460018127 No Department of Oral and Maxillofacial Surgery , Dentistry Faculty, Babol University of Medical Sciences, Babol, Iran Nima Nikafshar Nima.nikafshar@gmail.com 100319475328460018128 100319475328460018128 No Department of Oral and Maxillofacial Surgery , Dentistry Faculty, Babol University of Medical Sciences, Babol, Iran