Computed tomography findings predicting invasiveness of thymoma

To identify preoperative computed tomography (CT) findings associated with thymoma invasiveness before surgical resection and with clinical outcome.

We retrospectively reviewed CT scans of 99 patients with thymoma surgically treated at our institution between September 1999 and April 2010. Chest CT findings documented were size, volume, and heterogeneity of primary tumor; abutment of mediastinal vessels; and presence of calcifications, lobulation, infiltration of fat surrounding tumor, adjacent pulmonary changes, adenopathy, and pleural nodularity.

Our study group consisted of 53 (54%) men and 46 (46%) women, age 18-79 years (mean: 53.2 years). Masaoka pathologic stages were stage I for 10 (10%), stage II for 48 (48%), stage III for 21 (21%), and stage IV for 20 (20%). The median radiologic tumor size was 7 cm (range: 2.5-21 cm). A multivariable logistic regression model showed that primary tumors with prechemotherapy radiologic tumor size ≥ 7 cm (odds ratio [OR]: 3.18, 95% confidence interval [CI]: 1.16-8.67, p = 0.02), a lobulated tumor contour (OR: 8.20, 95% CI: 1.63-41.35, p = 0.01), and infiltration of surrounding fat (OR: 3.76, 95% CI: 1.45-9.78, p = 0.007) were more likely to have stage III or IV disease. Cox's proportional hazard model showed that the presence of pulmonary nodules on staging CT was the only imaging parameter associated with shorter progression-free survival (hazard ratio: 4.93, 95% CI: 1.60-15.17, p = 0.005) and overall survival (p = 0.03).

The primary tumor CT imaging features can differentiate between stage I/II and stage III/IV disease and, thus, help identify patients more likely to benefit from neoadjuvant therapy.