Mesenchymal tumours of the mediastinum--part I

Abstract

The mediastinum is an anatomically defined space in which organs and major blood vessels reside with surrounding soft tissue elements. The thymus is an important organ in the mediastinum, and many of the masses encountered in the mediastinum are related to this organ. Most neoplasms diagnosed in the mediastinum are epithelial tumours (thymomas and thymic carcinomas), lymphomas or germ cell tumours. In contrast, soft tissue tumours of the mediastinum are rare. In 1963, Pachter and Lattes systematically reviewed soft tissue pathology of the mediastinum, covering the hitherto described [2, 226, 227] In this review, based on the 2013 WHO classification of soft tissue tumours and the 2015 WHO classification of tumours of the lung, pleura, thymus and heart, we provide an updated overview of mesenchymal tumours that may be encountered in the mediastinum.

Keywords: Mediastinum; Mesenchymal tumours; Soft tissue tumours.

Fig. 1

Thymolipoma. Thymolipoma in a 43 year-old male, discovered incidentally during routine physical work-related examination. Mature fat with thymic tissue with discernable cortical and medullary compartments and minor cystic change (HE stain)

Fig. 2

Age distribution of thymolipoma with [21, 23, 24] and without [12, 14, 16, 17] myasthenic symptoms

Fig. 3

Angiolipoma (lipomatous hemangioma). Tumour in the superior mediastinum in a 67-year-old female who had few complaints but had persistent pleural effusion. The mass was excised, and no recurrence was noted after several years of follow-up. a Axial contrast-enhanced CT image revealing a circumscribed mediastinal mass with variable density. The mass was found to have been present for several years on retrospective evaluation of previous examinations. b Mature fat admixed with thin-walled vessels; there was no atypia of endothelial cells

Fig. 4

Liposarcoma with myxoid change. A posterior mediastinal mass, surrounding the aorta in a 55-year-old male discovered during routine health check (a). The mass was excised (b, c). A recurrence was excised 16 months later; there was no evidence of disease after 1-year follow-up. a Axial noncontrast CT image at the level of the left atrium revealing a smoothly marginated retrocardiac mass with variable attenuation. b Sagittal reformatted CT image showing the retrocardiac mass to extent from the aortic arch to the diaphragm. c Macroscopic image of the transected tumour revealing a fleshy, partially thinly encapsulated mass. d Microscopic image (medium power, HE stain) showing myxocollagenous stroma with scattered atypical mesenchymal cells

Fig. 5

Fat-forming solitary fibrous tumour. A large tumour in the chest cavity in a 23-year-old female who complained of shortness of breath. The mass was excised but later recurred and resulted in death of the patient. a CT image showing a large tumour that occupies the anterior and posterior mediastinum. b HE stain showing mature fat tissue admixed with ill-defined nodules of spindle cells with elongated nuclei and tapering cytoplasm. c CD34 stain which is diffusely positive in the spindle cells. d STAT-6 immunohistochemistry with diffuse nuclear and cytoplasmic positivity