RESUMO
Mesenchymal soft tissue masses are uncommon tumours of the chest. Myofibroblastoma is a recently described entity consisting of cells with origin from the myoepethelial cell, mostly seen as benign well-circumscribed neoplasms of the breast tissue. Though usually classified as a benign lesion, rarely it can be multifocal and prone to recurrence. We describe below the case of a 26-year-old female who presented with exertional dyspnoea and evidence of a massive mass lesion in the left hemithorax causing mediastinal displacement to the opposite side. On histological and immunophenotypic analysis, a diagnosis of the very rare thoracic myofibroblastoma was made. The incidence, salient features, pathological differential diagnoses and treatment are reviewed.