Diagnostic ultrasound ( PDFDrive )

CHAPTER 7 The Pancreas 249
TABLE 7.5 Pancreatic Endocrine Tumors (PETs)
Tumor Type Located in Pancreas Size All PETs
Hyperfunctioning
Insulinoma 90%-100% 2-3 cm 45%
Gastrinoma 40%-60% 1-2 cm 35%
Others 10%
VIPoma 90%
Glucagonoma 100%
Somatostatinoma 50%-60%
Carcinoid PET 100%
Nonhyperfunctioning
All tumors >5 cm 10%
VIP, Vasoactive intestinal polypeptide.
SMV
SMA
Ao
Stent
IVC
FIG. 7.84 Pancreatic Endocrine Tumor, Nonhyperfunctioning. Longitudinal
oblique color Doppler sonogram shows 5-cm, hypoechoic
malignant tumor large enough to cause bile duct obstruction, requiring
stenting. Internal color low is typical with pancreatic endocrine tumors.
Ao, Aorta; IVC, interior vena cava; SMA, superior mesenteric artery;
SMV, superior mesenteric vein.
FIG. 7.83 Insulinoma on Intraoperative Ultrasound. This 10-mm
lesion was discovered because of hyperinsulinism. (Courtesy of Dr.
Hisham Tchelepi.)
clinically—because of pain, 185 mass efect, or, if malignant, invasion
and metastasis 119 (Fig. 7.84). Incidental detection of smaller,
nonhyperfunctioning tumors is becoming more frequent (Fig.
7.85). hese tumors are usually well deined and round or oval.
hey generally appear hypoechoic compared to the normal
parenchyma. hese tumors may have cystic changes and calciication.
187 he larger, nonhyperfunctioning pancreatic endocrine
tumors may be diicult to diferentiate from the more common
pancreatic ductal adenocarcinoma. Sonographic indings that
suggest the diagnosis are (1) prominent internal color low (rare
in carcinoma), (2) lack of biliary or pancreatic ductal dilation
in a pancreatic head lesion, and (3) lack of progression or
metastasis on serial imaging.
Unusual and Rare Neoplasms
On ultrasound, many histologic variants of pancreatic ductal
adenocarcinoma are indistinguishable from tumors with the
usual histologic features. hese include adenosquamous cell
carcinoma, anaplastic carcinoma, and pleomorphic giant
cell carcinoma. Acinar cell carcinoma and pleomorphic
giant cell carcinoma, although oten indistinguishable from ductal
adenocarcinoma, may be larger and may exhibit central necrosis.
Primary pancreatic lymphoma is prohibitively rare, although
adenopathy or difuse involvement from more generalized
disease occurs with some frequency. 120 Other rare pancreatic
tumors include connective tissue–origin tumors (sarcomas),
pancreaticoblastomas, dysontogenetic cysts, and metastases. 190,191
Lipoma
In contrast to the usual echogenic appearance of fat and fatty
lesions, pancreatic lipomas are usually hypoechoic 192,193 (Fig.
7.86). Other lipomas may have a mixed appearance, with a variable
amount of internal echoes, or they may appear hyperechoic. he
cause of hypoechoic fat is not known but may involve the number