The physical examination findings and histopathologic changes were consistent with superficial necrolytic dermatitis, and
the plasma glucagon concentration strongly suggested that a glucagon-secreting pancreatic tumor was present. An exploratory
laparotomy was scheduled for 18 days after presentation. The dog's bacterial cystitis was treated.
LAPAROTOMY
5. The surgically removed mass and adjacent pancreatic tissue from the caudal pole of the right lobe of the pancreas (the
hemostat tip is adjacent to the mass).
After routine intravenous anesthetic induction, intubation, and establishment of a surgical plane of anesthesia with isoflurane,
a ventral midline laparotomy was performed. A 1-cm diameter multilobular mass was identified on the caudal pole of the right
lobe of the pancreas. The mass was removed (Figure 5) and submitted for cytologic and histologic evaluation. Postoperative recovery was uneventful.
CYTOLOGIC EXAMINATION
6. Cytologic examination of a scraping from the pancreatic mass revealed a monomorphic population of neoplastic mononuclear
cells in small cohesive groups with many cell-free nuclei typical of an endocrine neoplasm (modified Wright's stain, 500X).
The cytologic examination revealed that the scrapings of the pancreatic mass were highly cellular. The scrapings consisted
primarily of individual and small cohesive groups of neoplastic mononuclear cells mixed with many cell-free nuclei and erythrocytes
(Figure 6). The mononuclear cells also had round nuclei with coarsely stippled nuclear chromatin, and many of the cells had a single,
small prominent nucleolus. The mononuclear cells also had moderate amounts of light-blue to gray, indistinct cytoplasm; mild
anisocytosis, anisokaryosis, and a variation in the nuclear:cytoplasmic ratios were present. A few small cohesive clusters
of exocrine pancreatic glandular epithelial cells and low to moderate numbers of cytologically normal small lymphocytes were
also identified. The scrapings were cytologically consistent with an endocrine neoplasm.
HISTOLOGIC EXAMINATION
7. Histologic examination of tissue from the resected pancreatic mass revealed a discrete population of pale uniform neoplastic
cells adjacent to normal exocrine pancreatic glandular tissue (upper left and entrapped within the neoplasm) (hematoxylin-eosin
stain, 100X).
The histologic examination revealed that the section of pancreatic tissue consisted of a single, approximately 0.6-cm diameter,
nonencapsulated, poorly delineated neoplastic mass that had infiltrated the adjacent normal exocrine pancreatic glandular
tissue (Figure 7). The nodule was composed of round to polygonal neoplastic cells with lightly basophilic granular cytoplasm and round to
slightly oval vesicular nuclei with a single prominent nucleolus (Figure 8). Mild anisocytosis, anisokaryosis, and a variation in the nuclear:cytoplasmic ratios were present. Mitotic figures were
not seen, and no obvious vascular invasion was identified. A mild, multifocal lymphohistiocytic inflammatory infiltrate within
the tumor was also identified. Small groups of atrophic exocrine pancreatic glandular epithelial cells were trapped within
the neoplastic mass. The histologic examination results were consistent with a pancreatic islet cell tumor. The dog's prognosis
was poor because of the local invasion.
IMMUNOHISTOCHEMICAL ANALYSIS
8. Histologic examination of tissue from the resected pancreatic mass revealed round to polygonal neoplastic cells with lightly
basophilic granular cytoplasm and round to slightly oval vesicular nuclei with single prominent nucleoli, consistent with
a pancreatic islet cell tumor (hematoxylin-eosin stain, 400X).
The results of an immunohistochemical analysis performed at The University of Minnesota showed that the neoplastic cells were
immunoreactive for insulin, glucagon, and islet amyloid polypeptide. No neoplastic cells stained positively for pancreatic
polypeptide, somatostatin, or gastrin. These findings indicated that the pancreatic islet cell tumor was best characterized
as a glucagonoma of alpha pancreatic islet cell origin.
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