13
Respiratory Tract
Evidence exists that infection of the respiratory tract with
S. stercoralis
was rare before the introduction of steroid therapy.
Although migration through the respiratory tract is a part of the
life cycle of
Strongyloides,
the larvae ordinarily do not linger in
the lungs and produce, at most, minor irritation. In an immuno-
suppressed patient, hyperinfection in the gastrointestinal tract
occurs, and the organism apparently is capable of causing a
respiratory tract infection. In autopsies performed at our institu-
tion between 1930 and 1975, only two instances occurred of
respiratory tract infection with
S. stercoralis.
One was in a prema-
ture, debilitated infant. The second was in a patient with leuke-
mia treated with steroid therapy. Gocek and associates have
reported one case of unsuspected pulmonary strongyloidiasis
coexisting with adenocarcinoma of the lung.247 Vieyra-Herrera
and associates from Mexico have reported a fatal pulmonary
infection from the parasite in a patient with AIDS.250
Pulmonary Dirofilariasis
Dirofilaria immitis
is the dog heartworm. Mosquitoes feeding on
the blood of infected dogs ingest the infectious microfilariae. If a
human is bitten by such a mosquito, the infective larvae migrate
to the heart and die and are then carried into pulmonary arter-
ies. There they produce luminal obstruction and infarction. The
lesion produced appears on a radiograph as a 2- to 3-cm periph-
eral nodule. An FNA may show the worm with granulomatous
reaction. Seven cases (one diagnosed by FNA) were reported by
Ro and associates.251 Hawkins and associates have also reported
one case diagnosed by FNA.252
The infection has been reported by Akaogi and associates as
producing atypical cells mimicking lung cancer.253
Other Parasites
Also described in the respiratory cytologic literature are diag-
noses of pulmonary echinococcosis,254-260
Paragonimus kelli-
cotti,261,262 trichomoniasis,263
Entamoeba gingibalis,264 Entamoeba
histolytiea,
265
Paragonimus
westermani,266,267
microfilaria,268-270
Toxoplasma gondii,
and
Cryptosporidium.271
Inconclusive Cytologic Specimen
In prior sections of this chapter, emphasis has been placed on
those cytologic changes likely to become pitfalls for false-positive
cancer diagnoses. Another major issue that must be addressed in
the laboratory control of diagnostic accuracy is that regarding
the significance of inconclusive cytologic diagnoses, or those
diagnoses in which cytologic study is unable to confirm conclu-
sively the presence of cancer or to rule it out in the specimen.
The scientific literature on cytology of the respiratory tract is
ambiguous on this subject. Some investigators in the past have
chosen either to ignore these inconclusive diagnoses in their
studies or to group them together with positive cancer diag-
noses. Others have recorded them but did not evaluate them.
One of us (WWJ) has studied 205 patients in whose cytologic
specimens of sputum or bronchial material some variety of
an inconclusive diagnosis had been made.109 These data are
summarized in Tables 13.1 through 13.3. The most frequent
inconclusive diagnoses made were either atypical squamous
metaplasia or atypical cells suspicious for malignancy. In 70
patients, a cytologic diagnosis of atypical metaplasia was made.
In 28 of these patients, or 40% of the group, this diagnosis was
followed by a tissue confirmation of cancer (see Table 13.2).
In nearly one-third of these, the cancer was a squamous cell
carcinoma, with the other neoplasms scattered through various
other tumor types. In the remaining 42 patients, the follow-up
studies revealed the presence of some variety of non-neoplastic
disease, usually inflammatory in origin (see Table 13.3). In these
patients, various types of pneumonias composed the most fre-
quently associated category of disease. Some 135 patients had
originally been given a cytologic diagnosis of atypical cells sus-
picious for malignancy. In 92, or approximately 68% of these
patients, this suspicion of cancer was confirmed by tissue exami-
nation. In 43 patients, or approximately 32%, no cancer was
found. In this last group of patients, the most common underly-
ing disease process was pneumonia (see Table 13.1).
Risse and associates evaluated the significance of severe dys-
plasia in sputum samples.272 They defined dysplasia as the pres-
ence of atypical squamous metaplastic cells with an increased
nucleocytoplasmic ratio, hyperchromasia, and irregular nuclear
shape. In a group of 46 patients with diagnoses of severe
dysplasia on sputum, follow-up showed a malignant process in
21 patients (46%).
In 1964, Koss and associates reported cytologic results
obtained on 1886 patients for two 1-month periods.273 Of
these, 362 patients were proved to have cancer. A total of 63
diagnoses of "suspicious" (for cancer) were rendered. Of these,
38, or 60.3%, were among the proven cancer group. Among the
possible sources for diagnostic error, these investigators noted
viral pneumonitis, prior radiation, hyperplasia of the bronchial
lining, aspergilloma, and human error or judgment based on
insufficient evidence.
Williamson and associates have described a case of pulmo-
nary Wegener's granulomatosis in which markedly atypical
squamous cells present in specimens of bronchial washings
and brushings were erroneously interpreted as diagnostic for
squamous cell carcinoma.274
In a more recent study of 563 specimens from our labora-
tory, a diagnosis of atypical cells suspicious for malignancy was
found to have a positive predictive value of 85%.275
Pathology of Lung Cancer
The major focus of respiratory cytology is the diagnosis of lung
cancer. Thus, a chapter of this type would not be complete with-
out a discussion of this all too common disease. Although the
information provided in this section is but a brief overview of
the vast literature on carcinoma of the lung, the clinical, epi-
demiologic, and morphologic features discussed here should
provide a useful context within which the cytologic diagnosis of
lung cancer may be considered.
Carcinoma of the lung continues to be the most commonly
diagnosed noncutaneous malignancy in the world.276,277 In the
United States, it has long been recognized as the leading cause
of death due to cancer in males,278 and it has more recently
emerged as the most common cause of death due to malig-
nancy in females.279 The overall incidence of carcinoma of the
lung in some regions of the world including the United States
and much of western Europe has declined in recent years, largely
as a result of a decline in cigarette smoking among males in
these areas.277 Nevertheless, it is estimated that for the next year,
more than 213,000 new cases of lung cancer will be diagnosed
in the United States, and over 160,000 patients will die of the
disease.279
329
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