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incidence) and almost regularly involves the
common pancreatic duct (Fig. 34). Since
inflammation occurs around the hyperplastic
areas, it is hard to decide whether the
inflammation is the cause or sequence of
hyperplasia. In other strains, a lower incidence
(1%) of this type of lesion has been reported 133 . It
must be pointed out that in small laboratory
animals such as SGH, the "relative" incidence of
specific tumors depends on the histological
methods employed. The serial sectioning
technique, of course, guarantees an approach
more likely to determine the "real" value.
Figure 34. Papillary hyperplasia of the common
pancreatic duct. Note the mild peri-ductal
inflammatory reaction. H&E, X 50.
In contrast to endocrine tumors, which occur
predominantly in males, spontaneous tumors of
the exocrine parenchyma do not show significant
sex preferences. Although they have been found
only in males in some colonies, the lower
incidence of these spontaneous tumors
invalidates any conclusions as to sex preference.
Nevertheless, under experimental conditions,
females and males respond similarly, although
males are relatively more sensitive to the toxic
effects of the carcinogen, which is expressed by
their earlier death during the experiment.
Ductular tumors are within the range of
spontaneously occurring tumors in many hamster
colonies. They are definitely age-related lesions
and do not develop before 90 weeks in the Eppley
colony or 78 weeks in the Hannover colony 79 . The
incidence of ductular adenomas in the Eppley
32
colony was around 1%; in the Hannover colony,
1.5% 79 and in the Lakeview colony, around 2% 133,
134 . We observed local or multi-focal cystic
ductular tumors ranging between 1 to 3-mm nodules
(Fig. 35). Most of these tumors were located
in the tail of the splenic lobe, the largest
pancreatic segment in SGH.
Figure 35. Ductular adenoma in a 65-week-old
female hamster. The lesions are encircled by a thin
fibrous capsule. The involved islets (I) are cystic
with the rest of the islet cells fragmented. Note the
presence of inflammation (arrowhead) and ganglia
(arrow). H&E, X 32.
Spontaneous pancreatic adenocarcinomas were
not found in either the Eppley or Hannover
colonies. However, these tumors have been
reported in the Lakeview colony in a 0.3 to 1%
incidence 133, 134 . Adenocarcinomas are described
as a solid gray-white or hemorrhagic nodule of
variable sizes.
Most observed and reported endocrine tumors in
hamsters are of a spontaneous nature 78, 133-136 .
They develop occasionally in association with
ductular neoplasms, either as solid or more
frequently as mixed, ductular-insular cell tumors 87,
101 (Fig. 36). Islet cell tumors are characterized by
an immense vascularity that results in grayish red
or brownish-red nodules ranging in size between
1 to 30 mm. They can be of multi-focal origin (up
to four tumors), especially in the case of induced
lesions, 67% of which were multi-centric 137, 138 .
Adenomas can coincide with carcinomas in the
same animal. In analogy to the human situation,
most tumors (either spontaneous or induced)
arise in the tail region of the splenic lobe. The