The Pathology of Lumbosacral Lipomas: Macroscopic and Microscopic Disparity Have Implications for Embryogenesis and Mode of Clinical Deterioration

Abstract

Aims

Lumbosacral lipomas (LSL) are congenital disorders of the terminal spinal cord region that have the potential to cause significant spinal cord dysfunction in children. They are of unknown embryogenesis with variable clinical presentation and natural history. It is unclear whether the spinal cord dysfunction reflects a primary developmental dysplasia or whether it occurs secondarily to mechanical traction (spinal cord tethering) with growth. Whilst different anatomical subtypes are recognised and classified according to radiological criteria, these subtypes correlate poorly with clinical prognosis. We have undertaken an analysis of surgical specimens in order to describe the spectrum of histological changes that occur and have correlated the histology with the anatomical type of LSL to determine if there are distinct histological sub-types.

Methods and results

The histopathology was reviewed of 64 patients who had undergone surgical resection of LSL. The presence of additional tissues and cells types were recorded. LSLs were classified from pre-operative MRI scans according to Chapman classification.

95% of the specimens consisted predominantly of mature adipocytes with all containing thickened bands of connective tissue and peripheral nerve fibres. 91% of samples contained ectatic blood vessels with thickened walls, whilst 22% contained CNS glial tissue. Additional tissue was identified of both mesodermal and neuroectodermal origin.

Conclusions

Our analysis highlights the heterogeneity of tissue types within all samples, not reflected in the nomenclature. The diversity of tissue types, consistent across all subtypes, challenges currently held notions regarding the embryogenesis of LSLs and the assumption that clinical deterioration is simply due to tethering.

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