Diagnostic Cytology
Key features of poorly-differentiated squamous cell
• Mixture of single pleomorphic cells and tissue
• Tissue fragments arranged in "crab-like" clusters;
• Chromatin irregularly dispersed and hyperchromatic;
• Prominent nucleoli;
• Cytoplasm occasionally hyaline and cyanophilic; and
• Occasional keratinization.
A rare variant of squamous cell carcinoma, basal cell carci-
noma, may easily be confused with small-cell undifferentiated
carcinoma. Dugan has reviewed its cytologic characteristics in
two cases. He identified two features that he observed only infre-
quently in small-cell undifferentiated carcinoma: large, tightly
cohesive sheets and three-dimensional cell clusters, and cell
groups with a spindle cell pattern.371
Fig. 13.81 Poorly differentiated squamous cell carcinoma. Sputum
(Papanicolaou x OI).
In FNAs from squamous cell carcinomas, the specimen
reflects the degree of differentiation and tissue preservation
present at the site of the needle tip. When necrotic tumor with
large masses of keratinized squamous ghosts dominates the
cytologic picture, aspiration of a more peripheral portion of the
tumor increases the chance of obtaining diagnostic tumor cells.
A unique cytologic profile may be produced in sputum when
a keratinizing squamous cell carcinoma cavitates by extrud-
ing its necrotic core into the bronchial lumen. This picture has
been described in detail by Lavoie and associates.372 The back-
ground is extremely necrotic, with keratinized ghosts and an
intense inflammatory reaction. Markedly pleomorphic degen-
erating tumor cells with karyopyknosis are abundant. Cavitary
squamous cell carcinoma must be differentiated from a cavitary
fungus ball as discussed earlier in the infectious disease section
of this chapter. In the fungus ball, the specimen reveals atypi-
cal metaplastic cells, some severely atypical, rather than truly
malignant cells. Careful search of the specimen may reveal
the causative organism. It must be remembered, however, that
fungus balls may also arise in cavitary squamous carcinomas.
Squamous metaplasia with dysplasia is distinguished from
keratinizing squamous cell carcinoma by the lesser degree of
atypia in the former. In sputum, plant cells (see Figs. 13.41 and
13.43) may occasionally mimic keratinizing squamous cell car-
cinoma. Sheets of reactive or reparative epithelium exhibiting
prominent nucleoli and variation in nuclear size can be distin-
guished from poorly differentiated squamous cell carcinoma
by the more uniform chromatin and nuclear membranes, the
maintenance of cell polarity within groups, and the paucity or
absence of single cells in the reactive cases.
Depending on their location and size, adenocarcinomas may
exfoliate large numbers of diagnostic cells, few cells, or no cells
at all. Small peripheral tumors are least likely to provide diag-
nostic material in sputum or bronchial specimens. Although the
cellular pattern reflective of the adenocarcinoma group is readily
Table 13.10 Poorly Differentiated Squamous Cell Carcinoma
Cytologic feature
Bronchial wash
Bronchial brush
Mixture of single
pleomorphic cells and
tissue fragments
Chromatin irregularly
dispersed and
Prominent nucleoli
Cytoplasm hyaline but
Some tendency of
cytoplasm to form
refractile ringing
Large irregular sheets
Occasional cell may
show orangeophilia
BAL = bronchoalveolar lavage; FNA=fine-needle aspiration.
previous page 335 ComprehensiveCytopathology 1104p 2008 read online next page 337 ComprehensiveCytopathology 1104p 2008 read online Home Toggle text on/off