DOI:10.2214/AJR.05.1434
AJR 2006; 187:W357-W364
© American Roentgen Ray Society
Radiologic Findings that Mimic Malignancy
Angus R. O'Connor1 and
Charlotte Whittaker1
1 All authors: Department of Radiology, Nottingham City Hospital, Hucknall Rd.,
Nottingham, UK NG5 1PB.
Received August 16, 2005;
accepted after revision September 4, 2005.
Address correspondence to A. R. O'Connor.
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Abstract
OBJECTIVE. The purpose of this pictorial essay is to describe
selected variant anatomy, benign pathology, and posttreatment appearances that
may be incorrectly attributed to malignancy at cancer investigation.
CONCLUSION. Radiologists involved in cancer staging should be aware
of benign imaging appearances that simulate malignancy. Failure to correctly
identify these findings as such may lead to unnecessary patient anxiety,
incorrect tumor staging, and inappropriate treatment.
Keywords: benign • bone scintigraphy • cancer investigation • CT • malignancy • MRI • radiologic staging
Cancer patients routinely undergo intensive radiologic staging and
follow-up. Variant anatomy, benign pathology, or expected posttreatment
appearances may all be inadvertently attributed to tumor involvement,
resulting in overstaging of disease or erroneous diagnosis of recurrence.
Patients without a cancer diagnosis may also have imaging findings
inappropriately interpreted and undergo unnecessary surgery or percutaneous
biopsy procedures. In this pictorial essay, a selection of imaging findings
that may be mistaken for malignancy are illustrated and reviewed.
After radical orchidectomy for testicular tumors, a hematoma of the
spermatic cord may develop because of surgical handling or inappropriately
early postoperative mobilization. This can show a nodular appearance (Figs.
1A and
1B) on follow-up CT
examinations and be confused with lymphadenopathy. Carefully following the
connection with the spermatic cord should reveal its true nature and avoid
inappropriate chemotherapy.
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Fig. 1A —45-year-old man 3 months after radical orchidectomy for
malignant testicular tumor. Axial CT examination images are shown.
Inhomogeneous soft-tissue density (arrow) anterior to right external
iliac vessels is noted. Sections above and below show normal-diameter vas
deferens. This was caused by hematoma of spermatic cord.
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Fig. 1B —45-year-old man 3 months after radical orchidectomy for
malignant testicular tumor. Axial CT examination images are shown. Follow-up
examination 3 months later shows resolution of hematoma.
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A saphena varix is a focal dilatation of the saphenous vein at the junction
with the femoral vein, which can cause diagnostic confusion at CT when it
simulates an enlarged lymph node. Vascular continuity with the femoral vein
may be difficult to appreciate, especially if the varix traverses the lowest
section of the study. A recurrent varicosity with minimal vascular connection
may also be seen after varicose vein surgery (Figs.
2A and
2B).
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Fig. 2A —60-year-old man with low-grade lymphoma. Surveillance CT
examination images are shown. Lowest section of study shows oval density in
left groin (arrow), which was initially thought to represent lymph
node.
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Fig. 2B —60-year-old man with low-grade lymphoma. Surveillance CT
examination images are shown. Sonography examination shows hypoechoic oval
density, which was easily compressible and showed vascular connection with
femoral vein (arrow). Appearances are in keeping with varicosity.
Patient had undergone varicose vein surgery several years previously.
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Presacral soft-tissue masses are often seen after surgical resection of
sigmoid and rectal carcinomas. In most cases, they are caused by postoperative
granulation tissue and fibrosis. Imaging features supporting a benign cause
include symmetric shape, well-defined margins, and progressive reduction in
size on follow-up studies (Fig.
3). In the absence of symptoms and elevated tumor markers,
benign-appearing masses can usually be followed
[1]. They may persist for more
than 2 years after anterior or abdominoperineal resection; however, any
increase in size most likely indicates tumor recurrence.
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Fig. 3 —56-year-old man after anterior resection of colorectal
neoplasm. Well-defined, homogeneous soft-tissue mass (arrow) is seen
in presacral space, which remained stable on follow-up imaging. Appearances
are in keeping with fibrotic postoperative change. Density to right of rectum
is redundant bowel loop (L).
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Testicular epidermoid cysts are benign tumors accounting for only 1% of
intratesticular neoplasms. Although the appearances can be nonspecific, they
often show characteristic sonographic features
[2], including sharply defined
borders, well-demarcated acoustic shadowing, lack of internal Doppler signal,
and a markedly echogenic or hypoechoic border
(Fig. 4). When these
appearances are present, a confident preoperative diagnosis can be made, which
allows the surgeon to perform a simple enucleation of the cyst rather than
radical orchidectomy.
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Fig. 4 —34-year-old man complaining of painless lump. Transverse
sonogram through right testicle shows sharply defined mass with echogenic
border and acoustic shadowing. Appearances are those of epidermoid cyst.
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Bone graft harvesting sites at the iliac crest after spinal or
reconstructive head and neck surgery should be correctly identified as such
(Figs. 5A and
5B). A surgical tract is
usually seen in the overlying soft tissues, and consulting the operative notes
will make the findings conclusive.
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Fig. 5B —60-year-old man with preoperative CT scan obtained before
spinal decompression for liposarcoma metastatic to thoracic spine.
Postoperative imaging shows bone defect in posterior right ilium with
overlying linear high attenuation in subcutaneous fat. This was initially
interpreted as new metastatic deposit but was actually donor site of bone
graft.
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Pubic osteolysis is a rare destructive condition affecting the pubic bone
[3]. It has been reported in
postmenopausal women with underlying osteoporosis and, often, a history of
trauma. Radiographically, lytic bone abnormality is seen in the body or rami
of the pubic bone. Involvement of the symphysis pubis has been reported.
Histologic features may suggest chondrosarcoma or other primary bone
malignancy, compounding erroneous radiologic interpretation. Symptoms improve
with conservative management, and sclerotic interval change may be seen
radiographically (Figs. 6A and
6B).
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Fig. 6A —83-year-old woman complaining of diffuse pelvic pain after
fall. Pelvic radiographs are shown. Destructive lesion is seen in body of
right pubis with preserved cortex at symphysis. Sacral and rib fractures were
seen on bone scintigram (not shown). Because no clinical features were seen to
suggest systemic malignancy or infection, lesion was observed.
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Fig. 6B —83-year-old woman complaining of diffuse pelvic pain after
fall. Pelvic radiographs are shown. Follow-up radiography 2 months later shows
sclerosis of lesion. Patient's symptoms had resolved. Appearances are in
keeping with pubic osteolysis.
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Insufficiency fractures of the sacrum are easily confused with tumor
involvement because this is a frequent site of metastatic disease. Pain may
prompt investigation with bone scintigraphy or MRI. Increased scintigraphic
activity with fracture classically has the pattern of vertical bands through
the sacral alae, sometimes joined by a transverse fracture through the body
("Honda" sign) (Fig.
7A). Appearances may, however, be unilateral and have a more
rounded configuration, simulating metastasis
(Fig. 7B). On MRI, diffuse low
signal changes on T1 imaging with high signal on STIR sequences are seen. This
nonspecific appearance can be clarified by scrutinizing images for a linear
low-signal fracture line (Fig.
7C).
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Fig. 7A —Classic and atypical patterns of sacral insufficiency
fracture. 83-year-old woman with classical appearances of sacral insufficiency
fracture at bone scintigraphy. Squat view shows bilateral bands of increased
activity (fractures) in sacral alae, joined through further transverse
fracture ("Honda" sign).
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Fig. 7B —Classic and atypical patterns of sacral insufficiency
fracture. Bone scintigraphy, posterior view, in 70-year-old man previously
treated for prostate cancer with radical radiation therapy and antiandrogen
medication. Diffusely increased activity is seen in right sacroiliac region
with focus of markedly increased activity at lower right sacral ala
(arrow).
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Fig. 7C —Classic and atypical patterns of sacral insufficiency
fracture. Coronal T1-weighted MRI in same patient as B shows subtle
linear low-signal band (arrow) medial to sacroiliac joint in keeping
with stress fracture.
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External beam radiation therapy induces cytotoxic effects in bone,
resulting in photopenic defects on scintigraphy within the radiation field.
Such defects may be misinterpreted as lytic metastatic deposits and also may
disturb the symmetric appearance of the scintigram, leading the radiologist to
erroneously ascribe pathology to an area of normal activity that contrasts
with the appearances of the irradiated bone (Figs.
8A and
8B).
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Fig. 8A —28-year-old woman previously treated with radiation therapy
for synovial sarcoma in region of right iliac wing. Bone scintigraphy images
are shown. Posterior view shows diffuse photopenia from radiation therapy
effect in right iliac region altering usually symmetric distribution of
radionuclide in pelvis. Normal activity in left sacroiliac region should not
be mistaken for metastatic deposit or stress fracture.
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Fig. 8B —28-year-old woman previously treated with radiation therapy
for synovial sarcoma in region of right iliac wing. Bone scintigraphy images
are shown. Anterior view confirms diffuse reduction in activity throughout
right ilium with preserved anatomic contours.
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Hepatic hemangiomas typically have well-defined echogenic sonographic
appearances. In the presence of a background fatty liver, however, this
characteristic pattern may not be present; instead, a hypoechoic
[4] or target lesion
(Fig. 9A) can be seen that
could be incorrectly attributed to a metastatic deposit. In this situation, CT
shows the hemangioma to be isointense with fatty parenchyma on early
contrast-enhanced imaging. The usual delayed phase filling in or homogeneous
enhancement of the lesion is still seen (Figs.
9B and
9C). On an unenhanced study,
the hemangioma will be of increased attenuation relative to the background
fatty liver.
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Fig. 9A —76-year-old woman under investigation because of abnormal
liver function test results. Transverse sonogram of liver shows 16-mm target
lesion in right lobe (arrow). Note background parenchymal
echogenicity in keeping with fatty infiltration.
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Fig. 9B —76-year-old woman under investigation because of abnormal
liver function test results. Portal venous phase CT shows no obvious lesion.
Cluster of vessels (arrow) is seen in right lobe of liver.
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Fig. 10A —Atypical appearances of cysterna chyli. 79-year-old woman
with carcinoma of vulva who underwent staging CT scan. Round water density
lesion (arrow) is seen posterior to right crus at T11. No iliac or
paraaortic lymphadenopathy was seen, and lesion was unchanged on follow-up
study. Appearances are of prominent cisterna chyli.
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Fig. 10B —Atypical appearances of cysterna chyli. 44-year-old woman
with colorectal carcinoma. Well-defined left retrocrural density of water
attenuation (arrow) is noted, which remained unchanged on CT
examination. Appearances are of left-sided cysterna chyli.
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Fig. 11 —31-year-old woman in whom coronal whole-body FDG PET
examination shows symmetrically increased uptake in supraclavicular regions
(white arrows), in keeping with activity in brown fat. Increased
uptake is also seen in mediastinum (black arrow). This corresponded
with areas of mediastinal adipose tissue on coregistered CT images (not
shown), again in keeping with brown fat rather than lymphadenopathy. (Courtesy
of B. Franc, University of California, San Francisco, CA)
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Fig. 12A —76-year-old man with CT of thorax performed 6 months after
radical gastrectomy for carcinoma of stomach. Well-defined mass is seen in
left lung posteriorly, closely related to oblique fissure (arrow).
Appearances are in keeping with encysted effusion. Note right pleural
effusion.
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The cisterna chyli is a prominent retroperitoneal lymphatic channel behind
the right crus, at the T11-L1 level, which is visualized in less than 2% of
routine abdominal CT examinations
[5]. Characteristic features
include its location and well-defined homogeneous appearances of water
attenuation. It is usually small, but can measure up to 2 cm and should not be
confused with a lymph node (Fig.
10A). A left-sided cisterna chyli has also been described
[6]
(Fig. 10B).
Increased FDG activity of brown fat in the neck and supraclavicular regions
is a well-known variant at PET imaging
(Fig. 11). Less commonly seen
is mediastinal brown fat activity
[7], which can be mistaken for
lymphadenopathy unless corresponding CT images are inspected.
Encysted pleural fluid within the oblique fissure is well known to simulate
an intrapulmonary mass lesion on chest radiography, but it can be equally
deceptive on CT when only subtle connection with the fissure occurs (Figs.
12A and
12B). Although pleural
metastases in this location do occur, they are usually irregular or
asymmetric.
Carotid body tumors are rare benign neoplasms arising from the
chemoreceptor zone at the carotid bifurcation that usually present as a
palpable anterior triangular mass. Their characteristic imaging appearances
[8] include splaying of the
carotid vessels (because of their site of origin at the bifurcation), internal
vascular signal voids, and marked contrast enhancement (Figs.
13A and
13B). An incorrect diagnosis
of lymphadenopathy can lead to excision biopsy to exclude lymphoma, resulting
in severe hemorrhage and neurologic deficit.
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Fig. 13A —40-year-old man complaining of painless neck lump, which was
shown to be carotid body tumor. Axial unenhanced T1-weighted MR image of lower
neck shows soft-tissue mass (arrow), isointense with muscle, which
splays surrounding vessels.
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Fig. 13B —40-year-old man complaining of painless neck lump, which was
shown to be carotid body tumor. Enhanced sagittal T1-weighted image shows
marked enhancement. Characteristic site of origin of this tumor
(arrow) at carotid bifurcation is clearly shown.
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