13
Respiratory Tract
Table 13.8 Histologic Classification and Relative Incidence of Lung Cancer
Histologic type
Percent distribution
Armed Forces
Institute of Pathology72
Roswell Park572
Mayo Clinic602
Memorial Sloan-
Kettering157361
Duke University
Squamous cell carcinoma
40
38
30
33
39
Adenocarcinoma
(20)
(27)
24
45
(27)
Acinar
17
24
22
Bronchioloalveolar
3
3
5
Large-cell carcinoma
20
9
19
6
17
Small-cell carcinoma
20
19
26
16
16
Adenosquamous carcinoma
1
1
1
Fig. 13.73 Squamous cell carcinoma in situ. Sputum (Papanicolaou x OI).
cytology (3-day pooled sputum) three times per year. To date,
these studies have led to the detection of 58 in situ or early inva-
sive carcinomas. The investigators conclude from such studies
that cytologic techniques are of proven value in screening pro-
grams for the detection of in situ squamous cell carcinomas and
that conservative surgical resection of such lesions is associated
with a remarkably high cure rate for the disease.367
In specimens of sputum, the cells shed from in situ squa-
mous cell carcinoma appear as single small cells of round-
to-oval shape. The cytoplasm frequently is densely keratinized,
and the nuclei show obvious malignant features including
nuclear enlargement with increased nucleocytoplasmic ratios,
irregularity of the nuclear membranes, and dense hyperchro-
masia. Nucleoli may be present. Although some variation
in cell size and shape occurs, it is much less striking than the
bizarre extremes in pleomorphism seen in invasive squamous
cell carcinoma. Most cases also fail to show the necrosis and
inflammatory exudate more frequently observed in advanced
invasive lesions (Fig. 13.73). One may occasionally encounter
a population of uniform cells possessing a densely granular
chromatin and thin rim of cytoplasm virtually indistinguishable
from those cells shedding from carcinoma in situ of the uter-
ine cervix. It is agreed by most investigators, however, that in
situ squamous cancers of the lung do not shed a population
of cells that would permit an accurate distinction from invasive
cancer. Bronchial brushings may yield small tissue fragments or
Fig. 13.74 Keratinizing squamous cell carcinoma. Numerous ghost cells
and other cells with bizarre shapes are seen. Note the striking hyperchromasia
of the nuclei, the dyscohesion, and the hard-appearing cytoplasm. Sputum
(Papanicolaou x OI).
microbiopsy specimens of carcinoma in situ. The cytology of
squamous cell carcinoma in situ has been described in detail by
Woolner,367 Erozan and Frost,368 Koss,17 Kato and associates,369
Hayata,62 and Koprowska and associates.370
Invasive Squamous Cell Carcinoma
Invasive squamous cell carcinomas usually exfoliate large num-
bers of diagnostic neoplastic cells into the sputum, washings,
or brushings. In sputum, the neoplastic cells occur singly and
in loose clusters (Fig. 13.74). Tissue fragments are rare. Intact
keratin pearls and intercellular bridges, although important
in the histologic diagnosis of squamous cell carcinoma, are
uncommonly observed. Marked cellular pleomorphism is char-
acteristic of these tumors. Bizarre cytoplasmic shapes of almost
infinite variety may occur. Classic forms such as the caudate or
tadpole cell (Fig. 13.75), the fiber or spindle cell (Fig. 13.76),
and the "third-type" cell similar in morphology to that seen in
squamous cell carcinoma of the cervix are present (Fig 13.77).
The nuclei exhibit enlargement and marked hyperchromasia
with a tendency toward pyknosis. When the chromatin pattern
is preserved, it is arranged into irregular, sharp-bordered clumps
with abnormal clearing of the parachromatin. As a result of the
densely staining chromatin, nucleoli are observed less frequently
335
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