CT and MR imaging of melanocytic schwannomas; report of three cases.

Melanocytic Schwannomas are rare tumours which can arise in soft tissues, spinal nerve roots and in the central nervous system. The literature suggests that they have a malignant behaviour with local recurrence after surgery. We present three patients with this lesion, two in the thoracic spine and one in the head of the pancreas. The clinical outcome in these cases has been disappointing, since two patients died from complications due to local spreading of the tumour in spite of surgery and radiotherapy. CT could not distinguish these tumours from other neurogenic neoplasms. When these tumours occur near the vertebral body, CT could only detect early bone erosion. MR findings show promising features, with a high signal on T1-weighted images, due to melanin. However, more experience is necessary to establish the possible specific features of melanocytic Schwannomas in MRI.