Diagnostic Ultrasound - Abdomen and Pelvis

Pancreatic Neuroendocrine Tumor
Diagnoses: Pancreas
• Encapsulated lesion that more typically shows necrotic and
hemorrhagic features
Pancreatic Ductal Carcinoma (PDC)
• Infiltrative, solid mass, with ductal obstruction
• Poorly differentiated NET can be infiltrative
• PDC rarely shows necrotic change or calcification
Pancreatic Metastases
• Single/multiple small, well-defined, hypervascular lesion(s)
• Common primaries: Renal cell carcinoma and melanoma
Pancreatic Lymphoma
• Solid hypoechoic mass with intraabdominal
lymphadenopathy
Serous Cystadenoma of Pancreas
• Honeycomb lesion that can have heterogeneous echogenic
appearance on US
• Cystic components tend to be peripherally located with
enhancing septa and central scar
○ As opposed to central cystic area and solid enhancing
peripheral tissue with cystic NET
PATHOLOGY
General Features
• Etiology
○ Most are sporadic
• Genetics
○ 1-2% associated with familial syndromes: Multiple
endocrine neoplasia, type I (MEN1); von Hippel-Lindau
syndrome (VHL), neurofibromatosis, type I (NF1);
tuberous sclerosis complex (TSC1 and TSC2)
– Typically multiple, and present at younger age
Staging, Grading, & Classification
• Classification: Nonfunctional (60-80%) vs. functional
○ Nonfunctional tumors tend to be larger with poor
prognosis
• Functional tumors: Most commonly insulinomas
○ Insulinoma: Typically solitary and benign (90%)
○ Gastrinoma: ~ 60% demonstrate malignant behavior
○ Glucagonoma, vipoma, somatostatinoma: Rare and
most are malignant
• WHO grading of pETs (2010): Based on mitotic rate and
cell proliferation
○ Well-differentiated endocrine tumor
– Low and Intermediate grades
○ Poorly differentiated endocrine carcinoma
– High grade
○ Majority are well differentiated (97%)
○ No histologic criteria differentiates benign and
malignant tumors (except metastases)
– All tumors > 5 mm considered malignant
• TNM staging: Size (2 cm); extrapancreatic extension;
invasion of adjacent structure
Gross Pathologic & Surgical Features
• Round, well differentiated without capsule
• Large lesions: Small areas of degenerative
necrosis/hemorrhage are common
○ Usually central uniloculated area ± calcifications in 20%
○ 5-10% have extensive degeneration
Microscopic Features
• Sheets of small round cells, uniform nuclei/cytoplasm
resemble normal islet cells (uniform polygonal cells)
• Stippled salt and pepper chromatin; Eosinophilic granular
cytoplasm
• Electron microscopy: Positive neuron specific enolase
• ↑ serum chromogranin A (regardless of functional status)
○ 70% sensitive for detection of pETs
CLINICAL ISSUES
Presentation
• Most common signs/symptoms
○ May be incidentally detected if < 2 cm
○ Nonfunctional tumor: Usually asymptomatic; may
present with abdominal pain or mass effect
○ Insulinoma (Whipple triad)
– Hypoglycemia, palpitations, sweating, tremors,
headache, coma → IV glucose relief
○ Gastrinoma (Zollinger-Ellison syndrome)
– Peptic ulcer, esophagitis, and diarrhea
○ Glucagonoma (4D syndrome)
– Dermatitis, diabetes, DVT, and depression
Demographics
• Age
○ Peak: 4th-6th decades, younger in familial cases
• Gender
○ Overall no gender predilection, but subtypes do
– Insulinoma (F > M); gastrinoma (M > F)
• Epidemiology
○ Prevalence of 1/100,000 people
○ Account for 2-3% of all pancreatic neoplasms
Natural History & Prognosis
• All tumors > 5 mm considered malignant
• Cystic change/necrosis and calcification → poorer prognosis
• Indolent growth; metastasizes to nodes, liver, bone
• Insulinomas: Best prognosis, survival rate similar to general
population
○ Usually small and nonmetastatic at time of presentation
• Noninsulinoma NETs recur or metastasize in 50-80% cases
○ 5-year survival rate of 50-65%
Treatment
• Surgical resection is only curative treatment for NETs
○ Enucleation vs. partial pancreatectomy
• Chemotherapy: Poorly differentiated tumors
• Radionuclidetherapy: Tumors with somatostatin receptors
• Transarterial chemoembolization or radiofrequency
ablation for liver metastases
SELECTED REFERENCES
1. Sahani DV et al: Gastroenteropancreatic neuroendocrine tumors: role of
imaging in diagnosis and management. Radiology. 266(1):38-61, 2013
2. Klimstra DS et al: The pathologic classification of neuroendocrine tumors: a
review of nomenclature, grading, and staging systems. Pancreas. 39(6):707-
12, 2010
3. Lewis RB et al: Pancreatic endocrine tumors: radiologic-clinicopathologic
correlation. Radiographics. 30(6):1445-64, 2010
386