[Analysis of flow cytometric nuclear DNA content of the thymoma and its relationship to malignant intensity]

Determination was made of the nuclear DNA content of paraffin-embedded specimens of resected thymoma using flow cytometry in 39 patients. Relationships among nuclear DNA content, clinicopathological findings and prognosis were studied. The frequency of DNA aneuploid tumors was 30.8%, 6.7% in stage I (15 patients), 28.6% in stage II (7 patients), 44% in stage III (9 patients) and 62.5% in stage IV (8 patients) according to Masaoka's classification, indicating more in increase with advancing stage and significant (p less than 0.05) more increase invasive thymoma than in noninvasive thymoma. The 5 year and 10 year survival rates of DNA diploid tumors were each 94%, while DNA aneuploid tumors, 75% and 45%. Patients with DNA aneuploid tumors showed less favorable prognosis than those with DNA diploid tumors. Similar results were found in patients with invasive thymoma and in those on whom subtotal or partial resection were performed. The present results indicate DNA aneuploid tumors to have greater malignant intensity than DNA diploid tumors in resected thymoma. Flow cytometric nuclear DNA content analysis provides useful biological data and new indices for evaluating the malignancy of resected thymoma.