Elevated serum epidermal growth factor receptor level in stage IV thymoma

Using the enzyme immunoassay for epidermal growth factor receptor (EGFR), we investigated whether serum EGFR levels could be used as a predictor of the development and extension of thymoma. Serum samples were collected from 31 patients with thymoma and 16 patients with nonmalignant thoracic disease before clinical treatment. There was no difference between the serum EGFR levels of the patients with thymoma and the nonmalignant controls, being 49.1 +/- 136.3 and 22.6 +/- 7.3 fm/ml, respectively ( P = 0.11). However, patients with stage IV thymoma had significantly higher EGFR levels than those with stage I or stage II thymoma, the respective values being 127.8 +/- 243.9, 10.9 +/- 9.2 ( P = 0.02), and 19.7 +/- 10.6 ( P = 0.0433) fm/ml. The serum EGFR levels were similar in the pathological subtypes. These findings suggest that serum EGFR levels may serve as a marker that could be used as a diagnostic indicator of the invasion of thymoma.