Objective: To determine the prevalence of mediastinal mass, the histopathologic variations of mediastinal mass, and the predictive factors for diagnosis of lymphoma in Thai patients.

Material and Method: This retrospective hospital-based chart review was conducted in patients who were definitively diagnosed with mediastinal mass at Siriraj Hospital between January 1, 2011 and December 31, 2015. Demographic data, radiographic findings, and histopathology were collected and analyzed.

Results: Three hundred thirty two of 3,107,341 cases who received treatment during the study period were diagnosed with mediastinal mass for a prevalence rate of 0.01%. Mean age was 47.4±17.4 years. Gender distribution was 187 men and 145 women for a ratio of 1.3:1, respectively. Seventy-five percent of cases were symptomatic. Common symptoms included dyspnea (39.4%), cough (38.5%), weight loss (27.6%), and chest pain (23.9%). About 95% of masses were located in the anterior compartment. The histopathologic results were, as follows: thymic disorders (thymoma and malignant thymoma), lymphoma, metastatic cancer, and germ cell tumor in 45.8%, 21.7%, 12.9%, and 9% of cases, respectively. In multivariate analysis, patients with younger age (adjusted OR 0.93; 95% CI 0.91 to 0.96), fever (adjusted OR 4.78; 95% CI 1.31 to 17.36), intrathoracic lymphadenopathy (adjusted OR 3.57; 95% CI 1.49 to 8.58), and pericardial effusion (adjusted OR 3.46; 95% CI 1.23 to 9.72) were found to have increased probability of mediastinal lymphoma.

Conclusion: Mediastinal mass is a rare condition that affects all age groups with a prevalence of 0.01%. Thymic disorders are the most common cause. Predictive factors for diagnosis of lymphoma are younger age, fever, intrathoracic lymphadenopathy, and pericardial effusion.

Keywords: Mediastinum, Mediastinal mass, Thymoma, Lymphoma, Thailand