Histopathology of Synovial Cysts of the Spine

Abstract

Aims

Cystic lesions derived from the synovial and ligamentous structures of the spine have varied histologic appearances. Not uncommonly, there is discrepancy between the clinico-radiologic diagnosis and histology. Therefore, we sought to characterize the histologic features of tissue submitted as "synovial cysts" of the spine.

Methods

Resected specimens of the spine labeled "synovial cysts" and "lumbar cysts" were histologically evaluated and classified based on histopathologic features.

Results

75 histologic samples of spinal cysts were identified. 31 were classified as synovial cysts (definite synovial lining), 28 showed pseudocystic degeneration of the ligamentum flavum, 7 showed pseudocyst formation without evidence of synovial lining or degeneration of the ligamentum flavum, 8 showed cyst contents only or no histologic evidence of cyst wall for evaluation. Twenty-five cases (33%), especially those showing pseudocystic degeneration of the ligamentum flavum were associated with very characteristic tumor calcinosis-like calcium deposition with surrounding foreign-body giant cell reaction.

Conclusion

Histology of "synovial cysts" of the spine shows varied types of cysts; a large proportion are not synovial lined cysts but rather show pseudocystic degenerative changes of the ligamentum flavum often associated with very characteristic finely granular calcifications and foreign body giant cell reaction. This may have implications, not only in understanding the pathogenesis of these lesions, but also in their varied response to non-surgical interventions.

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