Recurrent Thoracic Intradural Extramedullary Calcifying Pseudoneoplasm.

A case of calcifying pseudoneoplasm of the neuraxis (CAPNON) that arose as an intradural mass of the thoracic spinal cord of a 53-year-old man, a motorcycle mechanic, is reported. The mass showed regrowth after the subtotal removal and was resected again 8 years later. Both primary and regrowth lesions consisted of calcified round nodules of the myxochondroid matrix rimmed by polygonal or short spindle cells. Fibrous tissue showing chronic inflammatory cell infiltration intervened between the nodules. Lamellar or woven bone tissue was also observed. In the regrowth lesion, the myxochondroid matrix was reduced in amount and partly replaced by fibrous tissue. Cells rimming the myxochondroid matrix were immunoreactive to epithelial membrane antigen and somatostatin receptor Type 2A, supporting the meningothelial origin. The pathogenesis of CAPNON remains obscure, but it is a nonneoplastic, probably reactive disorder to some unknown causes, and its close histopathological resemblance to tumoral calcinosis of somatic soft tissue suggests that both disorders share a common pathogenesis. Meningothelial cells surrounding myxochondroid nodules in the present lesions probably represent reactive meningothelial hyperplasia and reflect the locoregional specificity of the lesions. In the present case, some chronological changes of histopathological findings could be observed by comparing the specimens of two operations. Occupational mechanical overload to the vertebral column for a long term might have contributed to the pathogenesis of CAPNON.