Histologic evidence of absorption of sequestration-type herniated disc

The reactions to sequestrated disc fragments, which were removed surgically from 35 patients, were examined histologically. To elucidate whether or not there is histologic evidence of absorption of sequestrated discs. Spontaneous disappearance or diminution of lumbar herniated discs in the spinal canal has been recognized, and this could be a possible explanation for relief of symptoms without surgery. The mechanism of this phenomenon is unclear. Sequestrated discs removed surgically from 35 patients were examined histologically. In 30 cases, neovascularization was observed at the periphery of the sequestrated discs. Many foamy cells (macrophages) were present in the vascularized areas. In addition, immunohistochemistry revealed that many spindle-shaped, fibroblast-like cells were positive for CD68, a marker of macrophages. No fibrous scar formation was observed in any region. These findings suggest that organization is not a main course for this type of herniated disc and that a kind of "absorption" process occurs predominantly in the healing stage.