MR findings of a primary intramedullary malignant melanoma: case report and literature review

Abstract

A case of primary malignant melanoma of the conus medullaris depicted at MR imaging is presented. Tumoral histoimmunologic analysis revealed features of malignant melanoma. Because findings for primary melanoma outside the spinal cord were negative, the diagnosis of primary intramedullary malignant melanoma was established. This rare tumor should be suspected when T1-weighted images show signal hyperintensity and T2-weighted images show signal iso- or hypointensity, with mild contrast enhancement of the lesion. However, these features may vary depending on intratumoral bleeding and melanin content.

fig 1.

Sagittal T1-weighted MR image shows the spinal cord tumor at the level of the conus medullaris, which has a slight and homogeneous signal hyperintensity relative to that of the cord. fig 2. Sagittal T2-weighted MR image shows that the mass, compared with the spinal cord, is somewhat hypointense. fig 3. Sagittal contrast-enhanced T1-weighted MR image shows mild homogeneous enhancement in the tumor

fig 4.

Axial T1-weighted images demonstrate the intramedullary position of the tumor, which occupies nearly the entire spinal canal. A, Nonenhanced image. B, Gadolinium-enhanced image shows mild homogeneous enhancement in the lesion

fig 5.

Low-magnification photomicrograph shows that the tumor is highly cellular. Nuclear anaplasia has a tendency to form clusters of cells resembling the structure of a nevus (hematoxylin-eosin, magnification × 250). The inset shows the tumor invading the nervous structures (stars)

fig 6.

Photomicrograph shows that some nuclei of the epitheloid malignant cells contain nuclear inclusions (arrows) (hematoxylin-eosin, magnification × 1000). The inset shows that a large amount of melanin pigment masks the spindle-shaped malignant cells