A case of pleomorphic carcinoma of the lung 10 years after surgery for synchronous lung cancer and mediastinal lymph node carcinoma of unknown primary origin

Abstract

The patient was a 60-year-old male. Six years after thoracoscopic lung biopsy (right upper lung) for organizing pneumonia, an abnormal shadow was identified in the right upper lung on radiograph. Computed tomography (CT) of the chest revealed part-solid ground-glass nodules of 25 mm in the right S¹; however, no clear swelling of the lymph nodes was observed. On a diagnosis of right lung cancer, a right superior lobe resection and ND2a lymph node dissection were performed. Pathological examination revealed that the tumor in the superior lobe was well-differentiated adenocarcinoma; however, large cell carcinoma was observed in the 4^th mediastinal lymph node. Follow-up was conducted on the suspicion of synchronous double Stage IA, pT1N0M0 well-differentiated pulmonary adenocarcinoma and mediastinal lymph node large cell carcinoma of unknown origin. After 10 years of follow-up with no recurrence, a tumor suggestive of left superior lobe lung cancer appeared. On conducting left superior lobe resection, the tumor was histologically found to be pleomorphic carcinoma. The right superior lobe adenocarcinoma and left superior lobe pleomorphic carcinoma were considered unlikely to be the primary lesion of the mediastinal lymph node carcinoma of unknown primary origin. Mediastinal lymph node carcinoma of unknown primary origin is rare, and when incidentally discovered during surgery for lung cancer, the primary lesion may be hidden in the resected lung. If the primary lesion cannot be identified in spite of careful pathological examination, close follow-up is necessary.