Extradural vascular lesion of the spine mimicking a nerve sheath tumour

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Benign vascular lesions located in the spinal extradural space are rare, representing up to 4% of all spinal neoplasms. They are often misdiagnosed as nerve sheath tumours or meningiomas, based on their clinical and radiological features. In particular, only two cases of angioleiomyoma in the posterior mediastinum have ever been reported in the literature. We present the case of a 60-year-old man with a 12 month history of lower thoracic back pain radiating around the front of his ribcage to his epigastrium. MRI showed a solid, homogenous left para-spinal mass adjacent to the T11 vertebra, with no evidence of destructive changes or bony infiltration. Based on MRI, CT and FDG-PET studies this lesion was provisionally diagnosed as a benign nerve sheath tumour. He underwent successful surgical resection with remission of symptoms. Histological examination corroborated with immunohistochemis-try and special stains revealed a complex vascular lesion which, according to our knowledge has never been described before. Microscopic examination showed a circumscribed nodular lesion with vascular spaces of varying size. There were large muscular arteries with adjacent bundles of smooth muscle in the stroma. Other areas showed ectatic vascular spaces lacking a smooth muscle layer, lined by flattened endothelial cells, in myxoid stroma. These features clearly indicate the presence of an arteriovenous malformation with an extensive cavernous component, as well as a prominent angioleiomyomatous component. Besides highlighting the importance of histopathology in the diagnosis of these rare mimickers and the pitfalls of the differential diagnosis, we believe this case sheds relevant light on the hamartomatous nature of these rare and poorly understood entities.