Volumetric analysis of the thymic epithelial tumors: correlation of tumor volume with the WHO classification and Masaoka staging.

Background: The purpose of our study was to investigate the correlation between tumor volume (TV) and each subtype of thymic epithelial tumors (TETs) based on the World Health Organization (WHO) classification and Masaoka staging.

Methods: Sixty-one consecutive patients (45 thymomas and 16 thymic carcinomas) were studied. All were classified according to Masaoka staging: 31 non-invasive TETs (stage I) and 30 invasive TETs (8 stage II, 11 stage III, 3 stage IVa, and 8 stage IVb). TV on computed tomography (CT) were semi-automatically calculated using our software. The correlation of TV with each WHO subtype and Masaoka staging was analyzed using Mann-Whitney U and Scheffe's F test.

Results: Thymic carcinoma (mean ± SD, 117.5±143.6 cm3 ) was significantly larger than thymoma (53.4±78.4 cm3 ) (P=0.0016). Stage IVb tumor (190.8±156.8 cm3 ) was significantly larger than stage I (33.1±42.6 cm3 ) (P<0.05). Invasive TETs were significantly larger than non-invasive TETs (P=0.0016). TV >54.3 cm3 indicated invasive TETs.

Conclusions: TV of invasive TETs may be larger at the time of initial presentation. TV >54.3 cm3 indicates invasive TETs.