Melanotic cyst of L5 spinal root: A case report and review of literature

Abstract

Till date, 85 cases of melanotic schwannoma and 11 cases of spinal root melanoma have been reported in literature. We are reporting a case of a 45-year-old lady who presented with primary low back pain, and magnetic resonance imaging of lumbo-sacral spine showed at left L5-S1 foraminal lesion extending to the para-spinal compartment. Hemi-laminectomy, facetectomy, and excision of the lesion were done. It was primarily a cystic lesion with attachment to the exiting spinal nerve root. Histopathology of the cyst wall showed a fibro-collagenous stroma with no specific cell lining containing melanin pigment suggestive of a melanotic cyst. The patient was completely relieved of the back pain, and had no recurrence over a follow-up period of one and half years. This case is probably the first reported predominantly cystic, pigmented lesion, affecting the spinal root.

Keywords: Melanoma; melanotic; nerve sheath tumor; paraspinal; schwannoma.

Figure 1

MRI lumbo-sacral (a) axial contrast image, shows an extra-spinal heterogeneously contrast enhancing globular lesion with foraminal extension and widening, (b) MRI T1WI sagittal section at the level of left neural foramen shows a hypointense lesion arising at that level, (c) MRI T1WI contrast image of coronal section at the level of neural foramen shows heterogeneously enhancing lesion arising from the left L5 nerve root

Figure 2

Piece of the pseudo-cyst wall covered with jet-black shimmering coating

Figure 3

(a) H & E staining of the cyst wall shows fibro-collagenous stroma with interspersed ganglion cells and melanin pigmentation in the cyst, (b) pearls stain was negative for iron, (c) melanin bleach showed fibrocollagenous cyst wall devoid of pigmentation