AJR 2001; 176:695-699
© American Roentgen Ray Society
Pancreatic Parenchymal Metastases
Observations on Helical CT
John C. Scatarige1,
Karen M. Horton,
Sheila Sheth and
Elliot K. Fishman
1
All authors: Russell H. Morgan Department of Radiology and Radiological
Science, The Johns Hopkins University School of Medicine, Baltimore, MD
21287.
Received April 21, 2000;
accepted after revision June 20, 2000.
Address correspondence to E. K. Fishman, Department of Radiology, The Johns
Hopkins Hospital, 601 N. Caroline St., JHOC Rm. 3254, Baltimore, MD 21287.
Introduction
Metastases to the pancreas are rare, being found at autopsy in 3-12% of
patients with advanced malignancy
[1,
2]. Recent reports have
documented the value of CT both in showing the presence of pancreatic
metastases and in providing guidance to obtain a definitive tissue diagnosis
[1,2,3,4,5,6,7].
Several of these reports have emphasized the pivotal role of the radiologist
first in detecting the pancreatic mass and then in suggesting metastasis as
the likely diagnosis.
This pictorial essay will review the clinical features and the natural
history of pancreatic metastasis and will illustrate its varied appearance on
helical CT. In so doing, we hope to raise the radiologist's awareness of and
familiarity with this condition.
Clinical Features
Primary Tumors
Clinical and autopsy data indicate that a wide variety of nonlymphomatous
primary tumors may metastasize to the pancreas
[1,
2,
4,
5,
8]. The most frequently
reported sources are cancers of the lung, breast, kidney, gastrointestinal
tract, and thyroid; melanoma; hepatocellular carcinoma; and osteosarcoma.
Pancreatic metastases from melanoma, breast cancer, and lung cancer appear to
have a particularly high prevalence at autopsy
[9].
Symptoms
The symptoms produced by metastasis to the pancreas are variable. Most
patients (50-83%) are free of organ-specific complaints when the metastasis is
detected incidentally on CT during periodic clinical surveillance or follow-up
[2,
6].
Symptomatic patients may present with abdominal or back pain, nausea,
weight loss, jaundice, gastrointestinal bleeding, or obstruction
[2]. Pancreatic metastases can
directly invade pancreatic ductal epithelium and thus may clinically mimic
primary pancreatic adenocarcinoma or, less commonly, may induce acute
pancreatitis [1,
8].
Interval from Diagnosis
The interval from diagnosis of an extrapancreatic primary tumor to
subsequent detection of a pancreatic metastasis varies but is usually between
1 and 3 years [2]. In their
series, Klein et al. [4]
observed that the interval to diagnosis varied from as little as 2 months to
as long as 295 months; the longest intervals were associated with metastatic
renal carcinoma. Rarely, a pancreatic metastasis may be discovered before the
distant primary source is known
[2].
Treatment and Outcome
Pancreatic metastases usually develop late in the course of a generalized
malignant process and are frequently accompanied by concurrent extrapancreatic
metastases. Once a pancreatic metastasis had been detected, the mean survival
time was only 8.7 months in one series
[8]. Chemotherapy, hormonal
manipulation, or other palliative measures are usually used when appropriate.
Although most patients are treated without surgery, resection of solitary
pancreatic metastases from renal cell carcinoma may improve long-term survival
[8].
Findings on CT
The sensitivity of modern helical CT scanners in detecting pancreatic
metastasis is not known. A study published in 1989 comparing nonhelical
abdominal CT (9-sec scan time, 1-cm slice thickness) with autopsy results
found a true-positive rate of only 53.8%
[6]. The rate of detection of
pancreatic metastases will probably improve, however, as subsecond
multidetector helical CT systems become more widely deployed.
Lesion Distribution and Morphology
Metastases do not appear to show a predilection for a particular part of
the pancreas [3,
4]. Three patterns of
metastatic involvement of the pancreas have been described. The first and most
common, reported in 50-73% of cases, is that of a single localized mass
[5,6,7]
(Figs. 1 and
2A,2B).
The lesion tends to be large when first discovered, round or ovoid, well
marginated, and either isodense or hypodense when compared with the normal
pancreas on unenhanced images
[2,
4] Figs.
(3,4,5).
Distortion, compression, or obstruction of the common bile duct or main
pancreatic duct may occur, simulating primary pancreatic adenocarcinoma
[1,
2]
(Fig. 6). Although vascular
involvement is said to be uncommon
[4], splenic vein obstruction
and varices have been observed (Fig.
7).
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Fig. 1. —37-year-old woman with small cell variant osteosarcoma of
cervical spine and vague epigastric discomfort. Portal phase contrast-enhanced
helical CT scan reveals complex mass with thick enhancing septations arising
from head of pancreas and displacing distal stomach anteriorly. Note coarse
calcification (arrow). Imaging-guided fine-needle aspiration biopsy
confirmed metastasis from high-grade osteosarcoma resected 2 years
earlier.
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Fig. 2A. —50-year-old man with melanoma of scalp and pancreatic
metastasis seen on serial imaging. Routine contrast-enhanced helical CT scan
at level of pancreatic head reveals no abnormalities.
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Fig. 2B. —50-year-old man with melanoma of scalp and pancreatic
metastasis seen on serial imaging. Follow-up contrast-enhanced helical CT scan
at same level obtained 6 months after A reveals mass in pancreatic
head. Other CT scans (not shown) showed additional mesenteric and lymph node
metastases.
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Fig. 3. —62-year-old woman with recurrent ovarian adenocarcinoma.
Contrast-enhanced helical CT scan of upper abdomen shows hypodense expansile
metastasis in pancreatic tail and ascites resulting from peritoneal
carcinomatosis. Diagnosis was surgically confirmed.
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Fig. 4. —48-year-old man with small cell carcinoma of the lung,
previously treated with chemotherapy, who now complains of epigastric pain.
Contrast-enhanced helical CT scan through upper abdomen shows metastases in
pancreatic head (arrow) and left adrenal gland, which appeared after
earlier studies.
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Fig. 5. —29-year-old man with esophageal carcinoma, treated 3 months
earlier with esophageal stent, who is currently symptom-free. Helical CT scan
reveals hypodense metastases in tail of pancreas and right lobe of liver,
which appeared in 3-month interval.
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Fig. 6. —76-year-old woman with advanced bilateral breast carcinoma.
Contrast-enhanced helical CT scan reveals mass (arrow) in body of
pancreas with associated intrapancreatic fluid collection and duct dilatation
distal to lesion. Hepatic, left paraaortic, and intraperitoneal metastases are
also noted.
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Fig. 7. —76-year-old man with previous left nephrectomy for renal
carcinoma. Arterial phase helical CT scan reveals lobulated enlargement and
intense heterogeneous enhancement of pancreatic body and tail. Varices lateral
to stomach (arrows) and near splenic hilum indicate splenic vein
obstruction. Imaging-guided percutaneous biopsy confirmed diagnosis of
metastatic renal carcinoma.
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A second pattern of diffuse pancreatic enlargement has been reported in
15-44% of cases
[5,6,7].
The contour may be smooth or lobulated (Figs.
7 and
8).
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Fig. 8. —34-year-old woman with von Hippel-Lindau disease and
surgically confirmed diffuse pancreatic metastases from carcinoma of left
kidney. Partial left nephrectomy and distal pancreatectomy were performed 6
years earlier. Contrast-enhanced helical CT scan reveals markedly enlarged and
heterogeneously enhancing pancreas (arrows) that is little changed
during several years of observation. Pancreatic cysts are likely part of von
Hippel-Lindau disease.
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Finally, in 5-10% of patients, CT reveals multiple pancreatic nodules
[3,
5,6,7]
(Figs.
9A,9B
and
10A,10B).
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Fig. 9A. —68-year-old woman with small cell lung carcinoma.
Contrast-enhanced helical CT scan through body of pancreas reveals hypodense
lobular metastases (curved arrows) that enhance peripherally. Note
ductal dilatation and parenchymal atrophy (straight arrow) in
pancreatic tail.
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Fig. 10A. —37-year-old woman with metastatic small cell carcinoma of
uterine cervix established on biopsy and serial imaging. Contrast-enhanced
helical CT scan through pancreatic tail reveals hypodense metastasis
(arrow).
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Fig. 10B. —37-year-old woman with metastatic small cell carcinoma of
uterine cervix established on biopsy and serial imaging. Contrast-enhanced CT
scan through body of pancreas shows additional metastases (arrows).
Liver metastases were evident on other images.
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Several authors have observed that the morphologic and enhancement features
of a pancreatic metastasis on CT may closely resemble those of the distant
primary neoplastic source
[3,4,5]
(Fig. 11).
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Fig. 11. —50-year-old man with hepatocellular carcinoma diagnosed 9
years earlier and treated with hepatic resection. Pulmonary metastases were
recently diagnosed at lung biopsy. Contrast-enhanced helical CT scan through
pancreas reveals hypervascular metastases in tail of pancreas (white
arrow), portacaval space, and left lobe of liver (black arrow)
that were not present on earlier studies.
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IV Contrast Enhancement
Klein et al. [4] reported
the CT enhancement characteristics of pancreatic metastases in a series of 66
patients. Renal cell carcinoma and bronchogenic carcinoma accounted for 30%
and 23% of the primary sites, respectively. More than 75% of metastases
exhibited enhancement. The larger lesions enhanced peripherally, leaving a
central hypodense zone (Fig.
9A,9B),
whereas masses smaller than 1.5 cm in diameter enhanced more homogeneously
(Fig.
12A,12B).
Renal carcinoma metastatic to the pancreas merits additional comment because
it is both well studied and relatively common. Ng et al.
[3] recently reported a series
of nine patients who were examined with a three-phase contrast-enhanced
helical CT protocol. They detected 34 pancreatic metastases from 0.6 to 11 cm
in diameter. All metastases exhibited rapid enhancement on the arterial phase
beginning 25 sec from the start of injection (Fig.
12A,12B).
Lesion conspicuity was less dramatic on the 60-sec portal phase images and
diminished even further on the 120-sec delayed phase images.
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Fig. 12A. —63-year-old man with left renal cell carcinoma that was
treated 7 years earlier with left nephrectomy. Arterial phase of biphasic
helical CT scan reveals 2.5-cm mass (arrow) that exhibits early
enhancement in tail of pancreas.
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Fig. 12B. —63-year-old man with left renal cell carcinoma that was
treated 7 years earlier with left nephrectomy. Contrast enhancement of mass
(arrow) is less dramatic on later portal phase scan. Subsequent
distal pancreatectomy confirmed a solitary metastasis from renal cell
carcinoma.
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Extrapancreatic Metastases
Other sites of metastasis frequently accompany pancreatic metastases that
are discovered on CT (Figs. 4,
5, and
11). In one series of 20
patients with proven pancreatic metastases, 19 (95%) had one or more
additional extrapancreatic metastases
[5]. Indeed, the presence of
other metastases reinforces the likelihood that a pancreatic mass discovered
on CT represents metastasis.
The Radiologist's Role
Diagnostic radiologists performing body CT examinations on oncology
patients will encounter pancreatic metastases in their practices. The
diagnosis requires knowledge of the patient's primary neoplasm and familiarity
with the spectrum of CT appearances we have illustrated and described. At
times, pancreatic metastases may mimic primary pancreatic ductal carcinoma,
islet cell tumors, and pancreatitis. Rarely, the metastases may be discovered
before the primary site is known. When renal carcinoma metastasizes to the
pancreas, the findings on contrast-enhanced helical CT may be fairly specific
in the proper clinical context. Definitive tissue diagnosis is still necessary
in occasional cases when precise knowledge of the histology will alter patient
treatment.
Acknowledgments
We thank David M. Steinberg, Assistant in pathology and Clinical Fellow in
Cytopathology at The Johns Hopkins Hospital, for his invaluable assistance in
reviewing the pathologic material.
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Introduction
Clinical Features
