Primary Intradural Extramedullary Malignant Melanoma in the Thoracic Spine: Case Report and Literature Review

ABSTRACT

We present a case of primary malignant melanoma of the thoracic spine mimicking intradural extramedullary meningioma or schwannoma. In 2010, a 55-year-old man presented with hypesthesia below the T4 dermatome level and bilateral leg weakness. Magnetic resonance imaging (MRI) of the thoracic spine revealed an approximately 1.5 cm well marginated mass lesion in the intradural extramedullary area at the level of T4-5. Preoperative MRI findings suggested benign spinal cord tumor such as meningioma or calcified schwannoma. Surgery revealed a well marginated black-colored tumor. After removal of the tumor, we observed pigmented seeding along the leptomeninges. According to the pathology report, the final diagnosis was malignant melanoma. No evidence of primary malignant tumor, abnormal lymphadenopathy or distant metastatic lesion was found on the PET-CT scan. As a result, the lesion was compatible with primary spinal malignant melanoma. Even if spinal melanoma was suspected in the thoracic spine, it is easy to simply diagnosis the finding as schwannoma or meningioma based on the preoperative radiological findings. Therefore, preoperative diagnosis should be decided carefully, especially for masses in the thoracic spinal tumor.