Diagnostic ultrasound ( PDFDrive )

248 PART II Abdominal and Pelvic Sonography
presence of ovarian stroma in mucinous cystic neoplasm, these
tumors are now rarely diagnosed in men. 166,171 Mucinous tumors,
previously classiied as mucinous cystic neoplasms in men, would
likely now be considered IPMNs. Mucinous cystic neoplasms
may be benign, may have “low malignant potential,” or may be
overtly malignant. hus these tumors are generally managed as
malignant lesions.
Solid-Pseudopapillary Tumor
Solid-pseudopapillary tumor is the most recent name advocated
by the World Health Organization 172,173 and is found most frequently
in young female patients. Previous names include solid
and cystic tumor, solid and papillary epithelial neoplasm,
papillary-cystic neoplasm, papillary cystic epithelial neoplasm,
papillary cystic tumor, and Frantz tumor. About 15% of solidpseudopapillary
tumors are malignant. he likelihood of
malignancy increases with patient age. 154 Resection is generally
curative.
Solid-pseudopapillary tumors occur most oten in the tail
of the pancreas. hey are usually round, encapsulated masses 174
with variable amounts of necrotic, cystic-appearing areas and sot
tissue foci (Fig. 7.82). he cavities in solid-pseudopapillary tumors
are not “true” cysts but rather necrotic regions containing blood
and debris. 166 Central and rim calciications have been reported
FIG. 7.82 Large Solid-Pseudopapillary Tumor. Transverse sonogram
shows a large lesion in the pancreatic tail, the most common location
for these tumors.
Rare Cystic Pancreatic Tumors
Acinar cell cystadenocarcinoma
Cystic choriocarcinoma
Cystic lymphangioma
Cystic teratoma
Cystic pancreatic endocrine tumor
Metastases
in 29% of patients. 154 Buetow et al. 175 described 31 cases studied
with ultrasound, CT, and MRI and noted variable echotexture;
anechoic and hypoechoic areas were seen centrally. hrough
transmission was seen in all cases in which internal cystic areas
were grossly depicted, regardless of the echotexture.
Rare Cystic Tumors
Virtually any imaginable histology has been reported as a
“necrotic” or “cystic” lesion of the pancreas. 165,176-178 In general,
there is no characteristic ultrasound appearance for these rare
tumors.
OTHER PANCREATIC MASSES
Endocrine Tumors
Pancreatic endocrine tumors are a small but important group
of pancreatic neoplasms, previously called islet cell tumors or
neuroendocrine tumors; the current suggested terminology is
gastroenteropancreatic neuroendocrine tumors (GEP-NETs). 179
Formerly thought to arise from pancreatic islets, these tumors
are now believed to originate from neuroendocrine stem cells
in the duct epithelium. 180 hese tumors are rare, with an annual
incidence of approximately 5 cases per million. 181 Pancreatic
endocrine tumors constitute 1% to 5% of pancreatic neoplasms. 182
he two diferent presentations depend on whether there is
endocrine hyperfunction. 183 Hyperfunctioning lesions, about
90% of pancreatic endocrine tumors tend to present clinically
when the tumor is small. he endocrine manifestations cause
clinical symptoms before the tumor grows enough to cause
problems because of its size, invasion, or metastasis.
Insulinomas and gastrinomas are the most common hyperfunctioning
pancreatic endocrine tumors (about 80% of all
pancreatic endocrine tumors); others are rare (Table 7.5).
Hyperfunctioning pancreatic endocrine tumors tend to be
small, 1- to 3-cm (see Fig. 7.83), round or oval, hypoechoic
masses with smooth margins and, with the exception of insulinoma,
malignant. When a hyperfunctioning pancreatic endocrine
tumor is suspected, preoperative localization is appropriate.
Choice of modality depends on institutional preference and
includes transabdominal ultrasound, CT, or endoscopic ultrasound.
184 MDCT is superior to sonography in detecting small
endocrine tumors, 185 but sometimes ultrasound shows lesions
that are occult on CT. It is diicult to image pancreatic endocrine
tumors with conventional transabdominal sonography; they are
usually small when the patient presents with hormonal abnormalities.
Sensitivity of detection with ultrasound varies. Detection
rates for insulinomas range from 9% 186 to 65%. 184 he sensitivity
of ultrasound in the detection of gastrinoma is only 20% to
30%. 187 Sonographically, most hyperfunctioning pancreatic
endocrine tumors are small. Serotonin-secreting pancreatic
endocrine tumors may be associated with marked dilation of
the pancreatic duct. 188,189 Intraoperative sonography is the most
sensitive and accurate means of evaluating these neoplasms 184
(Fig. 7.83).
Nonhyperfunctioning tumors cause no endocrine-related
symptoms. herefore these tumors must be larger to present