2020 Volume 34 Issue 7 Pages 740-745
A 52-year-old man was referred to our hospital because of a cough and radiographic abnormality. Chest CT revealed a tumor of 53 mm in diameter in the anterior mediastinum. His preoperative serum squamous cell carcinoma antigen (SCCA) levels were markedly high (77.6 ng/mL) and serum anti-acetylcholine receptor (AchR) antibody levels were also slightly high (0.4 nmol/L). However, no autoimmune diseases including myasthenia gravis were identified. FDG-PET revealed abnormal accumulation at the mediastinal tumor (SUVmax: 3.4). The tumor was suspected to be thymic cancer and he underwent extended thymothymomectomy. Pathological findings showed a type B1 thymoma in WHO's histological classification and stage I in Masaoka's classification. Postoperative systemic evaluation showed no abnormalities including in the head and neck, dermatological, gastrointesitinal, and rectoproctal regions. Current serum SCCA levels are decreasing moderately 2 years and 6 months after surgery. Several reports showed discrepancies in laboratory data between immunoassays such as the chemiluminescent immunoassay (CLIA) method and fluorescence enzyme immunoassay (FEIA) method used to evaluate serum SCCA levels. The results in our case showed a marked difference (approximately ten-fold) between them. Here, we describe the clinical course of this patient and also discuss the mechanism of this difference, because this discrepancy might affect the dignosis of the tumor type.
