A case of cancer of unknown primary with mediastinal lymph node metastasis by CEA

Abstract

A 70-year-old man with a history of total gastrectomy for stomach cancer underwent periodic measurements of carcinoembryonic antigen (CEA). A mild increase in CEA level led to gastrointestinal fiberscopy, colonoscopy, positron emission tomography computed tomography (PET-CT), small bowel follow-through, and thyroid and abdominal ultrasound, which showed no findings indicating metastasis. Thereafter, a further increase in CEA level was associated with the swelling of the mediastinal lymph node accompanied by increased fludeoxy glucose (FDG) uptake, as revealed by PET-CT, suggesting a metastatic disease. Because no primary lesion was found, the possibility of false high CEA levels was taken into account and scrutinized by several tests such as the dilution linearity test, acetic acid extraction treatment test by chemiluminescent immunoassay (CLIA) method, heterophil antibody absorption test, scavenger-alkaline phosphatase (ALP) treatment test, and polyethylene glycol (PEG) processing test. As a result, the increased serum CEA levels were reconfirmed. Therefore, mediastinal lymph node dissection was performed for diagnosis and treatment. Tumor cells were positive for epithelial markers and lung adenocarcinoma markers, i.e., thyroid transcription factor 1 (TTF-1) and Napsin A, as determined by immunostaining, suggesting lung cancer metastasis, although it is not conclusive. In this case, the periodic measurements of CEA led to the diagnosis of lymph node metastasis. Furthermore, a battery of tests to exclude the possibility of nonspecific reaction persuaded surgeons to undertake lymph node dissection, which contributed to clinical management.