A surgical case of mediastinal lymph node carcinoma of unknown primary origin

Abstract

A 64-year-old man was referred to our institution because of an abnormal shadow of the mediastinum on a chest radiograph. Chest CT demonstrated a 50 mm mass in the middle mediastinum. The mediastinal mass showed high-level accumulation of FDG. Based on diagnostic imaging, we suspected a mediastinal tumor. We performed extirpation of the mediastinal tumor under thoracoscopic surgery. The specimen was confirmed as adenocarcinoma. Immunohistochemical staining suggested pulmonary adenocarcinoma to be positive for CK7, negative for CK 20, positive for thyroid transcription factor-1, and positive for napsin A. Pathological examination showed the adenocarcinoma to be of lung origin. Although whole-body examination failed to detect the primary site of the adenocarcinoma, this suggested the mediastinal lymph node carcinoma to be of unknown primary origin. Fourteen months later, brain metastasis occurred. We performed brain tumor resection. The patient was given platinum-based chemotherapy as adjuvant therapy. We encountered a surgical case of a rare mediastinal lymph node carcinoma of unknown primary origin.