Primary intramedullary melanocytoma in the thoracic cord: a case report and literature review

BACKGROUND: Primary intramedullary melanocytoma (PIM) is extremely rare, only 25 cases of PIM have been reported previously. Herein we report a case of PIM in the thoracic cord and reviewed its clinicopathological features, imaging features, therapeutic strategies and prognosis to provide helpful information in the diagnosis and treatment of PIM. CASE DESCRIPTION: A 56-year-old man presented with weakness and numbness in both legs for several years. Contrast-enhanced magnetic resonance imaging (MRI) of the spinal cord was performed. Based on the imaging examination, cavernous malformation with subacute hematoma was considered as the initial diagnosis. However, histopathological and immunohistochemical analyses confirmed the final diagnosis of PIM in the thoracic cord after surgical resection. The patient had no signs of recurrence or metastasis during a 17-month follow-up. CONCLUSIONS: MRI is the preferred method for the evaluation of PIM. PIM is characterized by a high signal on T1WI and a low signal on T2WI. It is difficult to make the differential diagnosis from cavernous malformation with hematoma before surgery due to its rarity. However, the symptom is not sudden but gradually worsened over a relatively long period in the PIM patients, which is an important difference from the cavernous malformation with hematoma. Therefore, PIM should receive diagnostic con¬sideration for an intramedullary lesion that is high signal on T1WI and low signal on T2WI in a patient with gradually worsened symptoms rather than sudden onset. It is of great importance for neurosurgeons and radiologists to recognize the characteristics of this disease, make the correct diagnosis in time and avoid delayed treatment.