Respiratory Tract
Fig. 13.24 Reserve cell hyperplasia. The nuclei are small and
hyperchromatic, with areas of striking nuclear molding. Bronchial brushing
(Papanicolaou x OI).
Fig. 13.26 Squamous metaplasia. The cells have sharp cytoplasmic
borders and nuclei that are not enlarged and that show uniformity of size
and fine chromatin. Sputum (Papanicolaou x MP).
Fig. 13.25 Squamous metaplasia. Sputum (Papanicolaou x MP).
be intensely karyopyknotic. Squamous metaplasias are capable
of undergoing changes characterized by increasing degrees of
nuclear abnormality. These metaplasias exhibit an increase in
nucleocytoplasmic ratio, a thickening of the nuclear membrane,
an increase in granularity and hyperchromasia of the chromatin,
and the appearance of nucleoli (Fig. 13.27). These abnormalities
have been called by various names, including atypical squamous
metaplasia and squamous metaplasia dysplasia.105-108 They have
been observed in the presence of long-standing chronic irrita-
tion of the tracheobronchial tree, particularly that caused by cig-
arette smoking, and they are believed by many investigators to
antedate the appearance of carcinoma of the lung. In about 60%
of patients, however, these atypical metaplastic cells are associ-
ated with non-neoplastic conditions of the lung, most notably
pneumonia (Tables 13.2 and 13.3).109 Figures 13.28 to 13.30
illustrate a particularly severe atypical metaplasia and hyperpla-
sia of type II pneumocytes occurring in a young adult. Atypical
metaplasia is discussed further in the section "Inconclusive
Cytologic Specimen."
Fig. 13.27 Squamous metaplasia with mild dysplasia. Sputum
(Papanicolaou x MP).
A special morphologic type of cell probably originating in
atypical squamous metaplasia is the so-called Pap cell, originally
seen by Dr. Papanicolaou in a specimen of his own sputum. He
described these cells as follows:
Cells with atypical features, which in some instances may
cause a suspicion of malignancy, are often seen in cases
of chronic inflammatory conditions including pneumonia,
tuberculosis and bronchiectasis. Some of these cells have a
distinctive form and therefore a diagnostic value, such as
the cell known in our laboratory as the “Pap" cell because it
was first noted 7 years ago in the author's sputum during an
exacerbation of a chronic inflammatory condition of the upper
respiratory tract. It is a relatively small acidophilic cell with
an elliptic form and an ovoid pyknotic nucleus. Dense clusters
of cells of this type have been seen in many cases of chronic
respiratory infections. In such cases a characteristic fading of
the nucleus is often noted, particularly in the later resolving
stages of the inflammatory process.
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