PART TWO
Diagnostic Cytology
Table 14.6 Cytomorphologic Differential Diagnosis of Poorly Cohesive Cells in Gastric Cytology
Feature
Carcinoid tumor
Signet ring adenocarcinoma
Lymphoma
Stromal tumor
Intercellular cohesion
Variably preserved
Poorly preserved
Absent
Variably preserved
Cytoplasm
Granular
Single dominant vacuole
Scant, nondescript
Scant to moderate, spindled
Nuclear contou rs
Round, smooth
Variable, sharp points
characteristic
Clefts, notches, indentations
Elongated
Chromatin pattern
Salt and pepper
granularity
Coarse
Usually fine
Usually fine
Nucleoli
- or inconspicuous
+
+, may be multiple
±
N/C ratio
High
Moderate
High
Moderate to high
Fig. 14.22 Carcinoid tumor. Dyshesive small uniform cells with
plasmacytoid features characterize this specimen (Diff Quik x MP).
mass that may ulcerate the overlying mucosa. Most often, the
neoplastic cells
are histologically arranged in anastomos-
ing trabeculae. The individual cells are small and uniform, as
each possesses a single round nucleus with stippled chromatin
and a moderate volume of variably granular and eosinophilic
cytoplasm. In general, there is little or no pleomorphism, mitotic
activity, or tumoral necrosis. Often, the mucosa is attenuated
but remains intact.
Only infrequently have the cytomorphologic features of these
neoplasms been described in GI brushings.1,160 In part, this may
relate to the fact that often the mucosa is intact over the carci-
noid tumor. Neuroendocrine neoplasms can also be diagnosed
more readily in transmucosal fine-needle aspirates.21 Smears
include homogeneous, small to moderately sized neoplastic
cells in variable numbers. Even at low magnification, the neo-
plastic elements are strikingly uniform. Each possesses a solitary
round or slightly ovoid nucleus with a delicate nuclear mem-
brane, finely to moderately granular chromatin, and possibly
small chromocenters or nucleoli. The chromatin is rather darkly
stained. Only thin rims of cyanophilic cytoplasm surround the
nucleus, yielding high N/C ratios. The cells are distributed as sol-
itary elements, as well as present in aggregates; the latter include
sheets, spheres, and acini. Especially in aspirates, the tumor cells
may be intimately adherent to the surfaces of delicate and at
times branched capillary blood vessels. Although the high N/C
ratios result in crowded nuclei, molding is not well developed
(Fig. 14.22). Among conventional carcinoid tumors, it is impos-
sible to predict accurately the biologic potential based purely
on histologic characteristics. Similarly, the benign or malignant
nature of a given neoplasm cannot be determined by cytomor-
phologic features.
Key features of carcinoid tumor
• Cellular smears of uniform small cells, both single and
aggregated;
• Generally scanty volumes of delicate cyanophilic may
be adherent to capillaries cytoplasm with high N/C ra-
tios; occasional cells with greater volumes, often with
eccentric nucleus;
• Nuclei: solitary, round to slightly ovoid, finely to mod-
erately coarse, evenly dispersed chromatin; nucleoli
may be small but evident;
• Molding not well developed; and
• Clean background.
The cytomorphologic differential diagnosis includes chronic
inflammation, malignant lymphoma, and small-cell carcinoma
(Table 14.6). The presence of intercellular cohesion militates
against both benign and malignant lymphocytes. Although the
N/C ratios are high in carcinoids, they are even higher among
lymphoid elements. The absence of nucleoli and of irregular
nuclear contours helps to exclude lymphoma. Much greater
levels of pleomorphism, prominent nucleoli, and loss of cohe-
sion would be expected in adenocarcinoma. Furthermore, it
would be most unusual for a carcinoid tumor to show evidence
of cytoplasmic mucin. Small-cell carcinomas are composed of
smaller tumor cells with higher N/Cs, more irregular nuclear
outlines, more obvious hyperchromasia, and molding. If immu-
nocytochemistry is performed, only the carcinoid tumor (and
small-cell carcinoma)
demonstrates diffuse neuroendocrine
differentiation.
Miscellaneous Lesions
In addition to
Helicobacter,
other organisms may be identified
in gastric cytologic specimens. These include
Candida,
CMV, and
various parasites.60,61,127
Candida
is probably not a primary path-
ogen, but rather secondarily colonizes preexisting ulcers, both
benign and malignant. CMV virocytes are usually associated
with systemic infection, most frequently with AIDS. Deposition
of amyloid, also as part of a systemic disorder, may occur in the
stomach and rarely be diagnosed in brushings.19 Very uncom-
monly, unusual neoplasms are recognized.161
394
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