Long-term polyvinylpyrrolidone storage. Histochemical and ultrastructural observations in two biopsy cases

Biopsy specimens of lymph nodes or bone marrow taken from two cases, which seemed to have received intravenous infusions of polyvinylpyrrolidone (PVP) more than 15 years ago, were examined histopathologically, histochemically or electron microscopically. In the lymph nodes, proliferation of foam cells, often with multinuclear giant cells, and basophilic vacuolar massive deposition were found markedly in the lymphatic sinuses and sporadically in the parenchyma. In the bone marrow, basophilic foam cells predominated, together with infrequent appearance of multinuclear giant cells and basophilic vacuolar deposits. The basophilic materials stored in the foam cells and multinuclear giant cells, as well as basophilic vacuolar massive deposits, were histochemically proved to stain with the special stains for demonstration of PVP. Electron microscopically, storage inclusions observed in the cytoplasm of PVP-storing macrophages were comprised of electrondense, amorphous substances or of vacuolar, fine reticulogranular, flocculent materials and were bounded by a single delimitating membrane. Most of the inclusions, particularly osmiophilic ones, showed intense acid phosphatase activity, while larger, vacuolar inclusions had a reduced or no enzyme activity. Extracellularly, vacuolar storage inclusions with no enzyme activity were found. The possible mechanism of long-term PVP storage in the tissues was briefly discussed.