13
Respiratory Tract
opaqueness. Cells previously classified as derived from the inter-
mediate cell subtype of small-cell undifferentiated carcinoma
possess slightly larger nuclei with a larger rim of cytoplasm and,
on occasion, conspicuous nucleoli.
Key features of small cell undifferentiated carcinoma
• Very small cells arranged in loose clusters with some
single cells;
• Individual cell about 1% times the size of a lymphocyte;
Table 13.14
Classification of Small-Cell Carcinoma
• Nuclei round to irregular in shape with very dense,
hyperchromatic chromatin;
• Karyopyknosis;
• Extremely scanty cytoplasm;
• Intercellular molding; and
• Necrosis.
In the combined type of small-cell undifferentiated car-
cinoma, the cellular specimen may reveal several morpho-
logic possibilities: It may show a combination of malignant
cells diagnostic for small-cell undifferentiated carcinoma and
malignant cells diagnostic for either squamous cell carcinoma
or adenocarcinoma,394,395 it may reveal malignant cells from
Cases
Percent
malignant cells from squamous cell carcinoma or adenocar-
cinoma only.
The cytologic presentation of small-cell undifferentiated car-
cinoma in bronchial brushings and FNAs can vary from one that
is characteristic to one that produces a significant problem in
differential diagnosis.396,397 (See also Fig. 13.105.)
Renshaw and associates reviewed 1185 interpretations of 23
different cases of small-cell undifferentiated carcinoma of the
lung in FNA specimens from the College of American Patholo-
gists Non-gynecologic Peer Comparison Cytology Program to
determine the frequency with which these neoplasms had been
misclassified as non-small-cell carcinomas. Those that were
Oat cell carcinoma
179
88.6
Intermediate cell
carcinoma
10
5.0
Combined“
13
6.4
Total
202
100.0
aSmall-cell carcinoma with foci of squamous cell carcinoma or adenocarcinoma.
Reproduced with permission from Johnston WW. Cytologic correlations. In: Dail
DH, Hammar SP (eds)
Pulmonary Pathology.
New York: Springer-Verlag, 1987.
Table 13.15
Small-Cell Undifferentiated Carcinoma
Cytologic feature
Sputum
Bronchial wash
Bronchial brush
BAL
FNA
Very small cells
arranged in loose
clusters with some
single cells
+
+
+
+
+
Cells arranged along
mucus threads
+
-
-
-
-
Individual cell is about
110 times the size of a
lymphocyte
+
+
+
+
+
Nuclei may vary from
round to very irregular;
chromatin is uniformly
dispersed but hyper-
chromatic to pyknotic
+
+
+
+
+
Nucleoli may be
present but are usu-
ally inconspicuous or
absent
+
+
+
+
+
Cytoplasm is extremely
scanty, presenting only
as a thin cyanophilic
rim
+
+
+
+
+
Intercellular mold-
ing is striking and an
important diagnostic
feature
+
A tumor diathesis may
be present
+
+
+
+
+
BAL = bronchoalveolar lavage; FNA=fine-needle aspiration.
345
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