Fig. 13.75 Keratinizing squamous cell carcinoma. Tadpole cells (caudate
cells). Sputum (Papanicolaou x OI).
Fig. 13.77 Keratinizing squamous cell carcinoma. "Third-type" cell.
Sputum (Papanicolaou x OI).
Fig. 13.76 Keratinizing squamous cell carcinoma. Fiber cells. Sputum
(Papanicolaou x OI).
Fig. 13.78 Keratinizing squamous cell carcinoma. Depicted is a
twisting between the keratinized and nonkeratinized cytoplasmic interface
(Herxheimer spiral). Sputum (Papanicolaou x OI).
than in other types of malignant neoplasms. They may, however,
be conspicuously large in some cells. Their presence is more
frequently associated with squamous cell carcinomas of a lesser
degree of differentiation. Nucleocytoplasmic ratios may range
from extremely high to very low owing to the marked variabil-
ity in the amount of cytoplasm produced by these neoplastic
cells. Keratinization of the cytoplasm is indicated by an intense
hyaline appearance with either a bright orangeophilic staining
or a deep cyanophilia. Ectoendoplasmic ringing or Herxheimer
spirals (Fig. 13.78), as described by Frost,24 are another striking
feature of abnormal keratinization in the cytoplasm. These
cytologic features are summarized in Table 13.9. In bronchial
specimens and FNAs, keratinizing squamous cell carcinomas
exhibit findings similar to those observed in sputum, although
tissue fragments are more common.
Key features of well-differentiated squamous cell
• Single cells;
• Striking pleomorphism with sharp cell outlines;
• Chromatin irregularly dispersed and densely
• Irregular keratinization;
• Irregular cytoplasmic thinning manisfested as caudate
and spindle cells;
• Ghost cells; and
• Keratin pearls.
As the differentiation of the squamous cell carcinoma
decreases, nuclear and cytoplasmic features of squamous differ-
entiation are less apparent (Figs 13.79 to 13.81). In sputum,
poorly differentiated squamous cell carcinomas appear as single
cells and cell clusters, whereas in bronchial brushing specimens
and FNAs, there is a noticeable tendency toward formation of
large irregular sheets of cells. The only cytologic evidence of
squamous differentiation may lie in the sharp appearance of the
cytoplasmic borders and in the tendency of the cells to form a
monolayer. The cytoplasm of these cells is generally cyanophilic.
Because of sampling, cells of squamous cell carcinoma obtained
by bronchial brushing or FNA may exhibit less differentiation
than those observed in sputum from the same patient. Cytologic
features of poorly differentiated squamous cell carcinoma are
listed in Table 13.10.