Primary intramedullary malignant melanoma: can imaging lead to the correct diagnosis?

Abstract

Melanoma is a malignant neoplasm of melanin-producing cells. Melanoma usually occurs in the skin, but can also arise in any anatomical site that contains melanocytes, such as mucous membranes, the eyes, and the central nervous system (CNS). Primary CNS malignant melanoma most often develops in the leptomeninges. We report a case of a rare intramedullary melanoma of the thoracic spinal cord. A 78-year-old man was treated with surgery, radiotherapy, and immunotherapy for leptomeningeal spread. We also discuss the role of imaging methods in diagnosis and follow-up. Medullary melanoma occurs more frequently in adults. The most common presenting symptoms are the insidious onset of lower extremity weakness and paresthesia. Magnetic resonance imaging is the method of choice for evaluation. Although there are no imaging features to accurately distinguish primary malignant melanoma from other melanocytic or hemorrhagic tumors, hyperintensity on T1-weighted magnetic resonance imaging should lead to inclusion of this neoplasm in differential diagnosis of spinal cord tumors. Positron emission tomography-computed tomography is a useful auxiliary examination to evaluate the extent of local and metastatic disease. Surgical resection is the primary treatment for intramedullary melanoma. However, the efficacy of adjunctive radiotherapy and chemotherapy for primary spinal cord malignant melanoma is still controversial.

Keywords: Spinal cord tumor; central nervous system; intramedullary melanoma; leptomeninges; magnetic resonance imaging; positron emission tomography-computed tomography.

Figure 1.

Primary intramedullary malignant melanoma of the thoracic spinal cord. Spinal magnetic resonance imaging shows an intradural and intramedullary expansive lesion at the T9–T10 level. There is a hyperintense signal on T1-weighted imaging without (arrow in a) and with fat saturation (arrow in b), and a hypointense signal on T2-weighted imaging (arrow in c), which is associated with discrete perilesional edema. (d) Positron emission tomography with 2-deoxy-2-[fluorine-18]fluoro-D-glucose integrated with computed tomography shows considerable uptake by the spinal cord lesion (arrow). There were no other suspected lesions.

Figure 2.

Post-treatment magnetic resonance images. Thoracic spinal magnetic resonance imaging, which was performed in the immediate post-treatment period, shows postoperative changes without suspected lesions on T1-weighted imaging with fat suppression before (a) and after intravenous gadolinium injection (b), and short tau inversion recovery (c).

Figure 3.

Recurrent melanoma in the surgical bed. Magnetic resonance imaging performed 6 months after completion of radiotherapy shows an expansive lesion with a hyperintense signal on T1-weighted imaging with fat suppression (arrow in a). This is associated with contrast enhancement and minimal leptomeningeal enhancement (arrow in b), which suggest recurrent melanoma.

Figure 4.

Recurrent melanoma and leptomeningeal spread. Magnetic resonance imaging performed 1 year after recurrence of the tumor and immunotherapy shows multiple leptomeningeal lesions. There is a hyperintense T1 signal in the interpeduncular cistern (arrow in a) and cervical (arrows in b) and thoracic (arrows in c) spinal cord segments, with contrast enhancement (arrows in d–f). These findings suggest advanced disease with progressive leptomeningeal dissemination.