There was prominent palisading of cells at the periphery of the epithelial nests
, giving the lesion a "basaloid" appearance (Figure).
Ki-67 labeled less than 5% of nuclei within the epithelial nests
, and nuclear p53 staining was seen in approximately 5% to 10% of tumor cells.
The possible pluripotential character of the embryonic epithelial nests
and the transformation of respiratory to squamous epithelium have been proposed to explain the various types of epithelial lining.
There were areas in which epithelial nests
were mainly composed of large clear or faintly granular cells, and peripheral palisading and reversed nuclear polarity were essentially absent (Figure 3).
The epithelial nests
displayed focal acantholysis and lacked any significant cytologic atypia (Figure 2).
In the center of the epithelial nests
were laminated layers and whorls of squames recognized as "wet keratin.