[A case of aggressive fibromatosis of posterior mediastinum].

Aggressive fibromatosis is a rarely seen soft tissue tumor. They originate principally from deep seated fascial or musculoaponeurotic structures. Although they are considered histologically benign, they behave locally aggressive. Posterior mediastinal localisation is very rare. The patient who was investigated because of a lesion located in posterior mediastinum and a thoracal magnetic resonance imaging revealed a mass with a dimension of 20 x 6 x 5 cm, started at the level of thoracal fourth vertebra reaching the L1 vertebra, was diagnosed as aggressive fibromatosis by a biopsy obtained after a right posterior thoracotomy performed by thoracic surgery. A minimal regression was established nine months after radiotherapy by thoracal MRI. This case of aggressive fibromatosis, which was asymptomatic and whose posterior mediastinal mass did not increased its dimensions during six years of follow-up, was presented.