Solitary neurofibroma of the psoas muscle: An unusual location

Neurofibroma is a benign peripheral nerve sheath tumour usually present on superficial tissues of the head and trunk. Retroperitoneal location is extremely rare for neurofibroma and comprises only 1% of all retroperitoneal tumours. It can be solitary or associated with the genetic disorder, von Recklinghausen's disease or neurofibromatosis type-1. Magnetic resonance imaging (MRI) is the gold standard modality for imaging retroperitoneal tumours because it provides a better definition and specificity in the evaluation of the location, extension, and composition of the lesion. Here, we report the case of a 30-year-old man affected by retroperitoneal solitary neurofibroma of the psoas muscle, but not associated with von Recklinghausen's disease. MRI showed a well-defined lobulated retroperitoneal lesion noted within the right psoas muscle. Complete surgical excision of the tumour was performed, and the diagnosis of neurofibroma was made through histological and immunohistochemical examination.