Respiratory Tract
Fig. 13.106 Small-cell carcinoma
in bronchial brushing. Note the dual
cell population produced by a mixture of well-preserved and necrotic tumor
cells. This is a helpful feature in differentiating this lesion from atypical
carcinoid. Bronchial brushing (Papanicolaou x OI).
Fig. 13.107 Small-cell carcinoma, intermediate cell type.
The nuclei,
on average, are somewhat larger than those of the oat cell type, and some
exhibit distinct nucleoli. Sputum (H&E x MP).
frequently misclassified ranged from 12 to 85%. The reviewers
concluded that misclassification correlated strongly with the
presence of cytoplasmic features that may suggest non-small-cell
In most cases, large numbers of tumor cells may be present.
The finding of tissue fragments is of diagnostic importance to
preclude lymphoma, but this differential may be more difficult
to determine than that in sputum. Most cells are well preserved,
with discernible nuclear chromatin pattern and occasional
nucleoli. They usually appear larger and show less molding than
when seen in sputum. A tumor diathesis is helpful in preclud-
ing carcinoid tumors, although the rarely encountered atypical
carcinoids may cause exceptional difficulty in the differential
diagnosis (Fig. 13.106). The tumors previously classified as
intermediate cell carcinomas in the experience of our laboratory
have caused the greatest interpretative difficulty, being at times
suggestive of poorly differentiated squamous cell carcinomas
(Fig. 13.107).
Table 13.16
Predictability of Cytologic Diagnosis of Small-Cell Carcinoma
in Histologically Confirmed Cases
of patients
of patients
Small-cell carcinoma
malignant neoplasm
Squamous cell
aTwo cases of intermediate cell carcinoma histologically; two cases of possible
atypical carcinoid histologically.
Reproduced with permission from Johnston WW. Cytologic correlations. In: Dail
DH, Hammar SP (eds)
Puim onaryPathoiogy.
New York: Springer-Verlag, 1987.
The ability of cytology to predict correctly the histology
of small-cell undifferentiated carcinoma is summarized in
Table 13.16 in a review of histologically confirmed small-cell
undifferentiated carcinoma in our laboratory. In no case did the
cytology incorrectly predict that a small-cell undifferentiated
carcinoma would be found; however, in five cases the cytology
revealed only squamous cell carcinoma components of tumors
later shown by histologic examination to be combined types of
small-cell carcinoma.
Adenosquamous Carcinoma
As discussed, the reported incidence of adenosquamous carci-
noma is related to the diligence with which histologic sections,
cytologic specimens, and electron microscopic preparations are
examined. The duality of differentiation of these neoplasms
may be reflected in the cytologic specimens. A diagnosis of
adenosquamous carcinoma should be entertained when a sin-
gle cytologic specimen of sputum, a bronchial brushing, or an
FNA exhibits malignant tumor cells in which there is evidence
of both keratin production and secretory activity.
Kamiya and associates compared the cytologic features of
32 peripheral squamous cell carcinomas with those of 31 hilar
squamous cell carcinomas. Most of the tumor cells in the periph-
eral neoplasms were arranged in irregular tissue fragments com-
posed of relatively small cells. Keratinization was seen in a small
number of isolated cells. In contrast the tumor cells in the hilar
neoplasms exhibited frequent keratinized cells and only a few
scattered small cells. Glandular characteristics were observed in
60% of the peripheral neoplasms but in only 10% of the hilar
ones. From these observations it was concluded that greater
than 50% of these peripheral tumors were adenosquamous
The majority of primary carcinoid tumors of the lung occur
within the walls of larger bronchi and probably originate in
bronchial submucosal glands. Although carcinoids typically
appear as exophytic endobronchial lesions, tumor cells are rarely
observed in sputum, because of the intact bronchial mucosa
overlying the tumor. In tissue sections, the tumor cells may
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