PMC4531604_01
Measurement of serum glucose on 72-hour fasting test. The arrow indicates the time-point of glucose administration
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The plasma insulin-to-glucose ratio was 1.41 (Table 1) and symptoms were immediately relieved following glucose administration (Figure 1).
Abdominal CT showed a single, round, well-enhanced mass in the tail of the pancreas, measuring 6 cm in diameter. Neither lymph node enlargement nor metastatic lesion was visible.
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A hypoechoic, heterogeneous echoic mass was discovered at the tail of the pancreas (Figure 2, 3).
Hypoechoic, heterogeneous with multiple anechoic spots and a smooth delineation without other intra-pancreatic occult mass were detected by EUS at a frequency of 7.5 MHz (G: stomach, M: mass, P: pancreas, S: superior mesenteric artery, V: splenic vein).
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A hypoechoic, heterogeneous echoic mass was discovered at the tail of the pancreas (Figure 2, 3).
The tumor mass was oval, well-demarcated solid, measuring 5.8x4.7x4.5 cm in dimension. Two foci of capsular invasion (arrowheads) were observed in the cut surface.
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The mass measuring 5.8x4.7x4.5 cm in dimension (Figure 4) was composed of uniform bland cuboidal cells with granular eosinophilic cytoplasm and round nuclei (Figure 5A).
The tumor demonstrated small nests of uniform bland cells septated by thin fibrovascular stroma (A). A peripancreatic lymph node was metastasized by tumor cells (asterisk) (B), (H&E. x100).
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The mass measuring 5.8x4.7x4.5 cm in dimension (Figure 4) was composed of uniform bland cuboidal cells with granular eosinophilic cytoplasm and round nuclei (Figure 5A). Two of four peripancreatic lymph nodes were metastasized (Figure 5B).
The cytoplasm of the tumor cells was strongly immunoreactive (dark-brown) for the insulin (A). A few tumor nuclei showed immunoreactive (dark-brown) for Ki-67 (B), (x200).
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Immunohistochemically, cytoplasm of tumor cells were strongly immunoreactive to insulin (Figure 6A) but not to somatostatin and glucagon. The Ki-67 labeling index (LI) was approximately 13% (Figure 6B).
EM demonstrated well-developed, membranous, electron-dense atypical secretory granules (SG) in the cytoplasm measuring 120 to 400 nm (A). There were wisps of non-branching intermediate amyloid filaments (asterisk) in the extracellular spaces (B). (M: mitochondria. Scale bar: 0.5 mum).
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On ultrastructural study, atypical secretory granules were easily found in the cytoplasm (Figure 7A). Amyloid deposits were showed both by electron microscopy (EM, Figure 7B) and congo red stain under polarizing microscopy (Figure 8).
Amyloid deposits near the vessels were exhibited yellow-green birefringence under polarizing microscopy (Congo red stain, x200).
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Amyloid deposits were showed both by electron microscopy (EM, Figure 7B) and congo red stain under polarizing microscopy (Figure 8).