Atypical indifferent (reserve) cells in the cervical epithelium and their exfoliative pattern

The ultrastructure of light microscopically selected atypical indifferent (reserve) cells in cervical smear preparations is described and compared with their ultrastructure in histologic sections. These atypical indifferent cells have a blastlike chromatin pattern and an intact nuclear membrane. The cytoplasm, however, was often damaged or absent; if present, it showed no sign of differentiation. In the histologic sections, these atypical indifferent cells were found in reserve-cell hyperplasia, in small numbers in squamoid dysplasia and as basally located cells in atypical endocervical epithelium. In contrast to the indifferent cells, the squamoid dysplastic cells and atypical endocervical cells in smear preparations had intact cytoplasm; however, the nuclear membrane of the squamoid dysplastic cells was often interrupted. This study indicates that atypical indifferent (reserve) cells can be recognized by light microscopy in smear preparations and that the fact that the cytoplasm is often damaged or absent is probably due to its undifferentiated nature. These cells can originate in pure atypical reserve-cell hyperplasia, dysplasia or atypical endocervical epithelium. In view of the great importance of these cells in the morphogenesis of squamoid and adenomatous carcinoma of the cervix, it seems of paramount importance that they be identified in cervical smears.