Diagnostic ultrasound ( PDFDrive )

CHAPTER 7 The Pancreas 243
TABLE 7.4 Estimated Prevalence of
Cystic Pancreatic Lesions a
SMV
Rank
Neoplasm
C
SMA
1 Intraductal papillary mucinous neoplasm
2 Serous cystic neoplasm (microcystic adenoma)
3 Mucinous cystic neoplasm
4 Solid-pseudopapillary tumor
5 Other cystic tumors
a Subjective estimate based on the authors’ experience.
IVC
LRV
FIG. 7.74 Benign Pancreatic Cyst (Presumed). Transverse color
Doppler sonogram shows 2-cm cyst discovered incidentally on abdominal
sonogram and followed for 4 years without a change in size. It is generally
safe to follow small completely simple pancreatic cysts (please see
text). Ao, Aorta; C, cyst; IVC, inferior vena cava; LRV, left renal vein;
SMA, superior mesenteric artery; SMV, superior mesenteric vein.
including symptomatic patients, growth of the cyst on serial
studies, tumor greater than 3 cm in diameter, internal sot tissue,
and mural or septal thickening. Multiple societies have proposed
algorithms to follow incidentally detected pancreatic cysts, 155
but there is a great deal of uncertainty in this process, 156,157 and
future assessment may rely on novel tumor markers and molecular
analysis rather than cross-sectional imaging morphology. 158 Data
from 2015 suggest that pancreatic cysts found incidentally by
using CT or MRI may be associated with increased mortality
for patients younger than 65 years and an overall increased risk
of pancreatic adenocarcinoma. 159
Simple Pancreatic Cysts
Simple pancreatic cysts are rare in the general population, with
a prevalence of 0.2% 160 to 1.2%. 151 hese low percentages may
underestimate true prevalence because imaging 161 and autopsy 162
studies have recorded a substantially higher prevalence, about
20% and 24.3%, respectively. Our experience suggests that the
lower prevalence rates are closer to the actual experience in
clinical imaging. Detecting a simple pancreatic cyst should raise
suspicion of an inherited disease that has a high prevalence of
Ao
High-Risk Features of Cystic Pancreatic
Lesions
Symptomatic patients
Growth on serial examinations
Diameter > 3 cm
Internal soft tissue
Mural or septal thickening
cysts, such as autosomal dominant polycystic kidney disease
(ADPKD) 163 or von Hippel–Lindau (VHL) disease. 164 Multiple
pancreatic cysts can also occur in individuals with cystic
ibrosis. 165
Multiple pancreatic cysts are more common in VHL disease
than in ADPKD. Prevalence of pancreatic cysts in patients with
VHL ranges from 50% to 90%, making pancreatic cysts the most
common type of lesion in VHL disease. 164 hus multiple simple
pancreatic cysts should suggest the diagnosis of VHL (Fig. 7.75).
In addition to simple cysts, other pancreatic lesions associated with
VHL include serous cystic neoplasm and pancreatic endocrine
tumors, with a slightly increased risk of ductal adenocarcinoma. 164
Cystic Neoplasms
Cystic tumors of the pancreas account for about 10% of cystic
pancreatic lesions. Although most solid tumors are ductal adenocarcinomas
with a poor prognosis, cystic tumors are usually
either benign lesions or low-grade malignancies. Malignant cystic
tumors account for about 1% of all pancreatic malignancies. 73
Mucinous tumors such as intraductal papillary mucinous neoplasm
and mucinous cystic neoplasm are oten malignant. he
risk of malignancy is greater in older individuals. Reliable
prevalence data are diicult to ind 166 but are estimated in
Table 7.4.
Serous Cystic Neoplasm
Serous cystic neoplasm, previously known as microcystic
adenoma, is typically a benign tumor, although a few invasive,
malignant examples have been reported. 73,166 Serous cystic
neoplasm occurs more frequently in women and is most oten
found in the pancreatic head. 154 hese lesions are composed of
myriad tiny cysts, generally too small to be individually resolved
sonographically (Fig. 7.76). he multiple relective interfaces
caused by the walls of the tiny cysts leads to an echogenic
appearance, analogous to that of autosomal recessive polycystic
kidney disease. hrough transmission is usual. Larger cysts
(1-3 cm in diameter) oten are present at the periphery of the
lesion. A radially oriented, ibrous pattern occurs in a minority
of patients, 149 and a central calciication is oten present (30%-
50%) (Fig. 7.77). Small lesions (<2 cm) may appear identical to
simple cysts. his pattern is common in the serous oligocystic
adenoma variant. 154