Distinguishing lipid pseudomembranes from larval cestodes by morphologic and histochemical means.

Abstract

Contributors regularly submit specimens to our institute and suggest a diagnosis of cestode infection, but the structures in question are actually lipomembranous changes that produce lipid pseudomembranes. This required a reproducible method to distinguish lipid pseudomembranes from body walls of cestodes. We describe and compare the morphologic and histochemical features of specimens from 20 patients. Nine specimens represented lipid pseudomembranes, and 11 represented one of the following five entities: cysticercus, coenurus, sparganum, hydatid of Echinococcus granulosus, or metastatic solid-bodied cyclophyllidean (possibly cysticercoid) larval cestodes. Specimens were stained with hematoxylin-eosin, Gomori's methenamine-silver, and 72-hour oil red O. Nine patients with cestodes, and all with lipid pseudomembranes, presented with subcutaneous lesions. In all specimens, oil red O provided marked contrast between lipid pseudomembranes and surrounding tissue, but focal or minimal contrast between larval cestodes and surrounding tissue. Unlike hematoxylin-eosin, Gomori's methenamine-silver stain produced distinctly different staining patterns in larval cestodes and lipid pseudomembranes. This technique readily permitted a simple, reproducible, and accurate distinction between lipid pseudomembranes and cestode body walls and distinguished between body walls of different cestodes.