It is rare to see such activity on the part of the epithelium as that
frequently encountered in influenza. The alveoli may be lined by newly
formed cubical cells (Figs. IV, XI, XLVII), and mitotic figures in the
injured bronchiolar lining occur in abundance. This might lead to the
supposition that, if the epithelium were restricted in its path of
development, it would pile up to form a typical nest, just as the
epithelium at the edge of a healing chronic ulcer of the skin may pile
up and extend fairly deep into the tissue. In a number of cases,
epithelial proliferation has been so extensive that it could not be
differentiated histologically from an invasive, malignant neoplasm (47)
(Figs. XLVIII and XLIX). There is no reason to believe that malignancy
might not result from the continuous stimulation of the epithelium to
proliferate, in the chronic inflammatory process of the lung in
influenza, just as chronic infection in the lung of a mouse results in a
much higher percentage of spontaneous neoplasms of the respiratory tract
in this species (132) than in those animals where chronic pulmonary
inflammatory processes are uncommon. It will be interesting, indeed, to
see whether, as a late manifestation, there is an increase in the number
of now relatively rare epithelial new growths in the respiratory tract
of man.
[Illustration:
FIG. XLVI. AUTOPSY NO. 128. THE ORGANIZATION IS HERE LARGELY CONFINED
TO THE INTERSTITIAL TISSUE. THE ALVEOLI ARE DISTORTED AND
COMPRESSED, AND THEIR EPITHELIUM HAS ASSUMED A CUBICAL FORM.
]
[Illustration:
FIG. XLVIII. AUTOPSY NO. 183. THIS DRAWING SHOWS A DILATED BRONCHUS
UNDERGOING OBLITERATIVE BRONCHIOLITIS. THE EXUDATE IN THE
SURROUNDING LUNG TISSUE IS BEING ORGANIZED. THE EPITHELIUM OF THE
BRONCHUS IS MANY LAYERS THICK AND HAS INVADED THE SURROUNDING LUNG
TISSUE. IT HAS THE APPEARANCE OF AN INFILTRATING EPITHELIAL
NEOPLASM. COMPARE FIGURES XI AND XLI.
]