Choroid plexus papilloma with stromal deposition of amyloid and elastic material

Congophilic birefringent amyloid deposits, with immunostaining for transthyretin (TTR) and amyloid P, associated with numerous coarse, enlarged and thick elastic fibres, are reported in the stroma of two choroid plexus papillomas, a finding not previously described in choroid plexus tumours. TTR was expressed as aggregates of 'doughnut-shaped' bodies, in which the TTR-positive peripheral area encircled the elastic fibre (TTR-negative core). Ultrastructurally, the amyloid microfibrils surrounded the elastic fibres and appeared to continue into the microfibrillar mantle of the latter. The stromal TTR-amyloid deposits associated with abundant elastic fibres in tumours that occur in the choroid plexus may be related to the alteration (production/accumulation, insufficient breakdown and/or extracellular matrix modifications) of some of the choroid plexus functions (removal, target and source of polypeptides, including TTR synthesis) and may be of interest for future studies on choroid plexus polypeptide activity and on protein development into elastomeric and amyloidogenic microfibrils.