Primary mediastinal neoplasms: a report of 1,005 cases from a single institution

This study was an epidemiological analysis of all primary mediastinal neoplasms (PMNs) diagnosed between 2000 and 2016 at the National Tuberculosis and Lung Diseases Research Institute, Poland.

All patients with any mediastinal abnormality were included in the analysis. The patients' age and gender were obtained from the institutional database.

From a cohort of 5,108 patients, 3,691 primary mediastinal lesions were found, including 1,005 (19%) PMNs: lymphomas (533, 53% of PMNs), thymomas (215, 21%), neurogenic tumors (NTs) (100, 10%), germ cell tumors (GCTs) (62, 6%), soft tissue tumors (STTs) (47, 5%) and thymic carcinomas/thymic neuroendocrine tumors (TCs/TNETs) (37 in total, 4%). The most frequent lymphomas were classical Hodgkin lymphomas [256] and primary mediastinal large B-cell lymphomas [163]. Type AB [73] predominated in thymomas and squamous cell carcinomas [9] and carcinoids [10] in TCs/TNETs. NTs encompassed mainly schwannomas [49], ganglioneuromas [21] and neurofibromas [10]. The most frequent STTs were hemangiomas [13] and lymphangiomas [11]. Lymphomas, thymomas and NT were more often in women, TCs/TNETs in men (P<0.001). Lymphomas predominated between the 2^nd and 4^th decade of life, NTs under the 3^rd decade and thymic epithelial tumors between the 6^th and 8^th decade (P<0.001). There was no correlation between the subtypes of thymomas and the patients' gender (P=0.389) but it was found between histology and patients' age: in patients <30 years of age type B2 and B3 thymomas and >70 years of age AB type and micronodular thymomas with lymphoid stroma (P<0.001) predominated. In the group of GCTs half of them were malignant and these were noted exclusively in men. No correlation between subtypes of NTs or TCs/TNETs and patients' age and gender was found (P>0.05).

PMNs are rare conditions thus awareness of basic epidemiology may be very helpful for final diagnosis.