14
Alimentary Tract (Esophagus, Stomach, Small Intestine, colon, Rectum, Anus, Biliary Tract)
Fig. 14.19 Gastric signet ring cell carcinoma. Small loosely cohesive cells are characterized by hyperchromatic, irregular nuclei, prominent nucleoli, and a
large mucin vacuole that abuts the nucleus, producing a signet ring cell-like configuration. The nuclear distortion frequently results in sharply pointed tips and
angles at the nuclear membrane rim (Papanicolaou x HP).
Fig. 14.20 Gastric lymphoma, large-cell type. Individually dispersed
large malignant lymphoid cells appear entrapped within a streak of
mucin. They have solitary nuclei with thick membranes, coarse chromatin,
and prominent nucleoli. The N/C ratios are high. There is no evidence of
intercellular cohesion (Papanicolaou x HP).
sharply pointed tips or long flat surfaces. Although histiocytic
nuclei may be bean-shaped, this does not result from distor-
tion by mucin vacuoles. Rather, cytoplasmic vacuoles in mac-
rophages tend to be small, multiple, and indistinct, conferring
a foamy appearance. The N/C ratio of carcinoma cells is higher
than those of either benign glandular elements or histiocytes.
If numerous (six or more) biopsies are obtained endoscopi-
cally, the vast majority of adenocarcinomas can be diagnosed
without the need for cytology. Several studies have shown
higher levels of diagnostic sensitivity and specificity of biopsies
over those of brushings.130,141,142 This is a reverse of the statistical
association in the esophagus. However, in both sites, the two
diagnostic modalities are complementary.
Malignant Lymphoma
Extranodal non-Hodgkin's malignant lymphomas arise most
often within the GI tract, with at least half of them occurring
within the stomach.143 Conversely, approximately 5% of all
gastric malignancies are lymphomas. Histologically, many of
these lymphomas fully resemble those seen as primary neo-
plasms of lymph nodes. In addition, there are types of lym-
phoid neoplasms unique to mucosa-associated lymphoid tissue
(MALT). Hodgkin's disease, especially as a primary neoplasm, is
exceptional in the alimentary tract. Most patients with primary
GI lymphomas are adults who may present with clinical pic-
tures referable to gastric ulcers, obstruction, or bleeding. In the
stomach, these most often occur as a solitary mass with focal
or diffuse involvement. Gross appearances include a polypoid
lesion, a mural nodule that is variably ulcerated, and massive
rugal enlargement. Although the endoscopic impression may be
that of a malignant tumor, its distinction from the more com-
mon carcinoma cannot be made reliably by the naked eye. Inter-
estingly Layfield et al. reported the value of FNA cytology for
excluding malignant lymphoma when prominent gastric folds
are present endoscopically.25 Histologically, almost any form of
malignant lymphoma may be encountered in the stomach, with
the diffuse large-cell type the most common. The vast majority
of gastric lymphomas have a B-cell lineage.
In cytologic brushings, smears contain numerous individually
dispersed monomorphic atypical lymphocytes.1,144-146 Although
the tumor cells may appear crowded, there is no evidence of
true cohesion or an organoid arrangement (Fig. 14.20). In
many instances, the lymphoma cells appear concentrated
within streaks of mucus. In large-cell lymphoma, each tumor
cell has a solitary nucleus with a thick and at times irregularly
shaped membrane, vesicular chromatin, and one or more well-
developed nucleoli. Cytoplasm is scanty, resulting in high N/C
ratios. In small cleaved cell lymphomas of follicular center cell
origin, the neoplastic elements are smaller with even higher N/
C ratios. Their chromatin is more darkly stained, nucleoli are
smaller, and well-defined indentations of the nuclear mem-
brane are evident in many cells. Although neutrophils may
be admixed with the tumoral elements, only very rare small
mature-appearing lymphocytes should be present. That is, as
in tissue, monomorphism of the lymphoid cells is crucial for
the cytologic diagnosis of lymphoma. It is difficult to diagnose
small lymphocytic lymphoma and the low-grade MALT-omas in
brushings.1,144
391
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