Hyperviscosity syndrome in disseminated breast adenocarcinoma

Circulation within the bloodstream of mucin derived from mucin-producing adenocarcinomas has been documented infrequently but has been associated with vascular occlusion, organ infarction, and hyperviscosity. The nature of the mucin and the therapeutic role of plasmapheresis in this condition has not been reported. A 64-yr-old female, who had undergone a mastectomy 3 yrs previously for an infiltrating mucinous breast adenocarcinoma, presented with dementia. A blood film showed marked rouleaux and a bluish background. No abnormal bands were detected on plasma protein electrophoresis. Blood, serum and plasma viscosity were above the range of readability of the viscometer. A bone marrow biopsy showed replacement with tumor similar to the original. Repeated plasmaphereses substantially reduced viscosity and temporarily improved her mental state. Post mortem revealed numerous infarcts with eosinophilic mucoid material in the lumen of many small vessels. That the offending plasma constituent was a sialomucin was suggested by mucin stains of the tumor and peripheral blood, a plasma sialic acid level 10 x normal and a substantial fall in viscosity after in vitro treatment of plasma with neuraminidase.