MCQ5.
Which one of the listed statements is the best histologic definition of an
abscess?
a. A circumscribed collection of neutrophils with necrotic cellular debris
b. A localized defect that results from the sloughing of necrotic inflammatory tissue
from the surface of an organ
c. A localized proliferation of fibroblasts and small blood vessels
d. An aggregate of two or more activated macrophages
e. The excessive secretion of mucus from a mucosal surface
AnswerThe answer is a. (Cotran, pp 84–87.) An abscess is a localized collection
of neutrophils and necrotic debris. It is basically a localized form of
suppurative (purulent) inflammation, which is associated with pyogenic
bacteria and is characterized by edema fluid admixed with neutrophils and
necrotic cells (liquefactive necrosis or pus). S. aureus classically produces
abscesses, because it is coagulase-positive and coagulase helps to produce
fibrinous material that localizes the infection. Other morphologic patterns
of inflammation include serous inflammation, fibrinous inflammation, and
pseudomembranous inflammation. Fibrinous inflammation is associated
with the deposition of fibrin in body cavities, which subsequently stimulates
coagulation. Histologically, fibrin is seen as amorphic eosinophilic
material. Fibrinous inflammation within the pericardial cavity (fibrinous
pericarditis) produces a characteristic “bread-and-butter” appearance
grossly. Serous inflammation produces a thin fluid, such as is present in
skin blisters or body cavities. In contrast to fibrinous inflammation, there
is not enough fibrinogen present in serous inflammation to form fibrin.
Pseudomembranous inflammation refers to the formation of necrotic membranes
on mucosal surfaces. Two infections classically associated with
pseudomembrane formation are Clostridium difficile, which produces a
characteristic “mushroom-shaped” pseudomembrane in the colon of people
taking broad-spectrum antibiotics, and C. diphtheriae, which produces
a pseudomembrane in the larynx.
In contrast to an abscess, an ulcer is a defect of epithelium in which
the epithelial lining is sloughed and is replaced by inflammatory necrotic
material. A localized proliferation of fibroblasts and small blood vessels
describes granulation tissue, while an aggregate of two of more activated
macrophages refers to a granuloma. The excessive secretion of mucus from
a mucosal surface refers to catarrhal (phlegmonous or coryzal) inflammation,
such as seen with a runny nose.
