Malignant melanotic nerve sheath tumors in the spinal canal of psammomatous and non-psammomatous type: Two case reports

Figure 1 A 58-year-old female with psammomatous melanotic schwannoma. A: Axial T1-weighted image of 11-12^th thoracic spine level shows low signal mass lesion (arrows) located in the intradural space; B: Axial T2-weighted image shows the mass lesion (arrows) with heterogeneously high signal intensity and the spinal cord (thick arrow) is displaced and compressed by the mass lesion; C: The mass lesion (arrows) represents heterogeneously strong enhancement containing necrotic portion on sagittal fat-suppressed, contrast-enhanced T1-weighted image; D: Amorphous linear calcification (black arrow) is noted in the peripheral margin of the mass on the computed tomography scan; E: Section shows spindle-shaped Schwann cells with brownish pigments, psammoma bodies (hematoxylin and eosin, × 100); F: Positive immunoactivity for S-100 protein that are characteristic features of psammomatous melanotic schwannoma (× 100).

Figure 2 A 72-year-old male with non-psammomatous melanotic schwannoma located in the spinal cord. A: Sagittal T1-weighted image of thoracolumbar spine shows a well-defined round-shaped nodular mass lesion (arrow) with increased signal intensity in the spinal cord of T11 level; B: The mass reveals dark signal intensity (arrow) such as a signal void on a sagittal T2-weighted image; C: On the corresponding axial T2-weighted image, high signal edema adjacent to dark signal intensity lesion (arrows) is noted in the spinal cord; D: The mass shows uniform homogenous enhancement (arrows) after gadolinium-contrast injection. It is eccentrically located on the right side within the distal spinal cord; E and F: On diffusion-weighted imaging and an apparent diffusion coefficient map, signal void (arrows) is noted within the mass without diffusion restriction; G: Section reveals a spindle cell lesion with dense melanin pigmentation that covers the nucleus and cytoplasm (hematoxylin and eosin, × 200); H: Immunostaining shows diffuse red staining for S100 protein (× 200).