Nose, Epithelium - Accumulation, Hyaline Droplet
comment:The presence of hyaline droplets ( Figure 1 , Figure 2 , Figure 3 , and Figure 4 ), which is seen in both mice and rats, is characterized by the accumulation of eosinophilic, homogeneous, globular, hyaline material in the cytoplasm of cells of the respiratory epithelium, sustentacular cells of the olfactory epithelium, or epithelial cells of seromucous glands. The droplets may be subnuclear or supranuclear and can distort the cells. They are occasionally accompanied by intra- or extracellular eosinophilic crystals. The junction of the olfactory and respiratory epithelia is a very common site to see this change, particularly on the nasal septum of the level II section and in the dorsal meatus. The material has not been definitively identified, but it has been reported to react to antibodies for carboxylesterase and the Ym1 sequence of the Ym2 protein. The droplets are found in low numbers in control rats and mice and increase with age. The number and size of droplets can be exacerbated by treatment, but it is not considered a degenerative change.
recommendation:Because the hyaline droplets can be found in control animals, diagnosis of this as a lesion ("Accumulation, Hyaline droplet") should generally represent an increase in the size and/or number of droplets relative to controls. If there is no difference between the control and treated animals, this change need not be diagnosed. When diagnosed this lesion should be assigned a severity grade, and the epithelial type should be included in the diagnosis as the site modifier. Since this is not considered a degenerative change, any concurrent cellular degeneration should be diagnosed and graded separately.
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