AJR 2005; 184:1910-1914
© American Roentgen Ray Society
Desmoplastic Small Round Cell Tumor in the Abdomen and Pelvis: Report of CT Findings in 11 Affected Children and Young Adults
Richard Bellah1,
Lisa Suzuki-Bordalo1,
Eric Brecher1,
Jill P. Ginsberg2,
John Maris2 and
Bruce R. Pawel3
1 Department of Radiology, The Children's Hospital of Philadelphia, 34th and
Civic Center Blvd., Philadelphia, PA 19104.
2 Division of Oncology, The Children's Hospital of Philadelphia, University of
Pennsylvania School of Medicine, Philadelphia, PA.
3 Department of Pathology, The Children's Hospital of Philadelphia, University
of Pennsylvania School of Medicine, Philadelphia, PA.
Received February 13, 2004;
accepted after revision September 15, 2004.
Address correspondence to R. Bellah.
Abstract
OBJECTIVE. Our objective was to evaluate the CT features of
desmoplastic small round cell tumor (DSRCT) of the abdomen and pelvis in
pediatric and young adult patients.
CONCLUSION. Characteristic CT features of DSRCT include bulky
intraabdominal soft-tissue masses that involve omental and serosal surfaces,
without a distinct organ of origin; solid, dominant, heterogeneous pelvic
masses in the retrovesical or rectouterine spaces; and concurrent metastases,
common at the time of diagnosis, particularly those involving lymph nodes and
liver.
Introduction
Desmoplastic small round cell tumor (DSRCT) is a rare but highly
aggressive neoplasm that afflicts mainly adolescents and young adults. The
most common location is the peritoneal cavity, although tumors arising from
other sites have been described. Fewer than 200 cases have been reported in
the literature, and only a few have included a description of radiologic
findings
[1-6].
We describe the CT findings and pattern of metastases in 11 children,
adolescents, and young adults with abdominopelvic DSRCT and discuss
differential diagnoses in this age group.
Subjects and Methods
Institutional review board approval was obtained for this study. Between
1994 and 2003, 13 patients with DSRCT were diagnosed or treated at The
Children's Hospital. Two patients were excluded from this series; one patient
had undergone initial imaging at another institution and the imaging studies
were not available for review, and one patient had extraabdominal
(paratesticular) DSRCT as the primary manifestation. All remaining 11 patients
underwent abdominopelvic CT at presentation, before treatment. Eight patients
also underwent chest CT before treatment. Contrast-enhanced abdominopelvic CT
had been performed with Siemens Somatom and Philips MX8000 scanners. Two
authors retrospectively reviewed clinical presentations and all imaging
studies for tumor size, location (including location of the largest mass), and
characteristics (enhancement and calcification). Secondary abdominal findings
(lymphadenopathy, liver metastases, ascites, urinary tract obstruction, and
bowel obstruction) and secondary thoracic involvement (lymphadenopathy,
pulmonary nodules, pleural effusion, and pericardial effusion) were also
analyzed. Findings were correlated to the outcome of the patients. DSRCT was
diagnosed with pathologic confirmation by surgical biopsy in all 11 patients
and by excisional biopsy in one patient.
Results
Eight of the patients were male, and three were female (age range, 10-20
years; mean, 14.5 years; median, 14 years). Common clinical presentations
included abdominal pain and weight loss (six patients [55%]), change in bowel
habits (four patients [36%]), and back pain and abdominal mass (three patients
[27%]). One patient presented with nausea and vomiting, and one patient
presented with abdominal distention.
Abdominopelvic CT findings and follow-up are summarized in
Table 1. All patients had
multiple omental, serosal, or mesenteric masses (Figs.
1A,
1B, and
1C). Nine patients (81.8%) had
dominant masses in the retrovesical or rectouterine spaces, with dimensions
that varied from 6 to 25 cm (mean, 14.3 cm) (Figs.
1A,
1B, and
1C). Isolated dominant masses
in the upper and mid abdomen were seen in only two patients (18.2%) (Figs.
2A,
2B, and
2C). Ten patients (91%)
presented with masses larger than 10 cm. All dominant tumors displayed
heterogeneous enhancement after IV contrast administration. Scattered
amorphous or punctuate tumor calcification was seen in six patients (54.5%)
(Fig. 2A). Six patients (54.5%)
had associated lymphadenopathy, either in the retroperitoneum or in the
mesentery. Small amounts of ascites were present in seven patients (63.6%).
Liver metastases were found in six patients (54.5%). These metastases appeared
as hypoattenuating nodules with variable sizes (ranging from 0.8 to 12.7 cm)
and number (solitary to multiple). Pelvic tumor involvement caused partial
urinary tract obstruction in five patients (45.5%) and variable bowel
dilatation due to partial bowel obstruction in two patients (18.2%).
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Fig. 1A. —13-year-old boy with abdominal pain and distention.
Contrast-enhanced abdominopelvic CT scan shows diffuse studding of peritoneal
surfaces and omentum by multiple soft-tissue masses (arrowheads) and
lymphadenopathy (n).
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Fig. 2A. —10-year-old girl with large mass in left upper quadrant.
Axial unenhanced abdominopelvic CT shows large, solid heterogeneous mass with
scattered calcifications (arrowheads) within lesser sac.
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Fig. 2C. —10-year-old girl with large mass in left upper quadrant.
Photomicrograph shows nests and cords of small, round undifferentiated cells
(arrowheads) separated by myxomatous desmoplastic stroma.
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Among eight patients who underwent chest CT at the time of initial
presentation, four (50%) showed lymph node enlargement measuring 1.0-4.0 cm in
the shortest axis. The lymph node groups most commonly involved were the
internal mammary and paracardiac lymph nodes, seen in three patients (37.5%).
Mediastinal nodal groups that were less commonly involved included right
paratracheal, subcarinal, prevascular (two patients), aortopulmonary window,
left paratracheal, right hilar, and retrocrural (one patient). Pleural
effusion was seen in two patients (25%). Pericardial effusion and thickening
were seen in one patient. Eight of 11 patients died from the disease. Three
patients are alive; one is in treatment without a favorable response, one is
in treatment for relapsed disease (32 months after diagnosis), and one is free
of disease (9 years after diagnosis). Abdominopelvic or chest CT findings had
no significant correlation with the outcome of patients.
Discussion
DSRCT belongs to the family of "small round blue cell tumors"
commonly found in the pediatric population. These include neuroblastoma,
malignant lymphoma, rhabdomyosarcoma, Ewing's sarcoma, Wilms' tumor, and
primitive neuroectodermal tumor (PNET). Previous reports indicated that DSRCT
most commonly affects male adolescents and young adults. In our study,
distribution by sex confirmed this male preponderance (male-female ratio of
3.8:1). The typical age range at diagnosis is 18-25 years, although DSRCT has
been described in older patients
[7,
8]. In our series, the mean age
at diagnosis was 14.5 years (range, 10-20 years). The younger mean age seen in
our series likely reflects the referral pattern of younger patients to The
Children's Hospital.
Gerald and Rosai [9] first
described DSRCT in 1989. In 1991, Gerald et al.
[7] proposed DSCRT as a
distinct entity when specific histologic, immunohistochemical, and karyotypic
features of the tumor were realized. Before that time, DSCRT might have been
classified as an atypical variety of small round cell tumors or as an unusual
form of malignant mesothelioma, adenocarcinoma, carcinoid tumor, or germ cell
tumor. The most striking histologic feature of DSCRT is the desmoplastic
stroma that envelops the tumor cells. This stroma is generally densely
collagenous or fibromyxoid and encases well-defined nests of primitive
undifferentiated cells (Fig.
2C). Focal areas of nonenhancement or low attenuation noted on
contrast-enhanced abdominopelvic CT possibly represent fibrous components of
these tumors, in addition to necrosis. These tumors are strikingly
polyphenotypic when analyzed with immunohistochemistry. They often display
reactivity for mesenchymal, epithelial, and neural markers, a feature that is
useful in distinguishing them from PNETs, lymphomas, rhabdomyosarcoma, and
other pediatric tumors with a small round blue cell appearance. From the
standpoint of karyotype, DSRCT shows a characteristic balanced translocation
involving chromosomes 11 and 22, similar to PNET and Ewing's sarcomas. In the
case of DSRCT, the translocation creates a unique fusion chimeric transcript
involving the WT1 (Wilms' tumor) and EWS (Ewing's sarcoma) genes.
The histopathogenesis of DSRCT remains unknown. Because most DSRCT arise in
the peritoneal cavity without a primary visceral site of origin, most
investigators believe that the tumor originates from the mesothelium (or from
submesothelial or subserosal mesenchyme), which is most extensive in the
peritoneum [7]. DSCRT has also
been described at other sites, including the paratesticular region, pleural
region, lung, ovary, sinus cavity, central nervous system, and stomach. All
patients in our series presented with masses in the peritoneal cavity.
Most patients with DSRCT come to clinical attention because of vague
gastrointestinal or genitourinary discomfort secondary to extrinsic
compression by the tumor. Because patients often initially present with
abdominal pain or large, palpable abdominal masses, CT is most often used for
initial diagnosis. Because, at the time of initial diagnosis, disseminated
tumor with multiple abdominopelvic masses and metastases (liver or lymph node)
often exists, CT is also most often used for staging and follow-up. Similar to
others
[1-3,
5,
6], we found the most common
abdominopelvic findings to be multiple, low-attenuation soft-tissue masses in
the omentum or mesentery or along abdominopelvic peritoneal surfaces, without
a distinct organ of origin. Tumor calcification, liver metastases, abdominal
lymphadenopathy, ascites, urinary tract obstruction, and bowel obstruction
also have been documented in previous studies
[1-3,
5,
6]. A striking feature of our
study, not emphasized in previous reports, was the presence of a dominant mass
in the retrovesical or rectouterine space (seen in 82% of our patients). We
speculate that the dynamics of the natural flow of peritoneal fluid, and the
dependent location of the pouch of Douglas, account for the prevalence of
malignant implants in this location. It is also not surprising that tumor
deposits were frequently noted in other known sites of peritoneal fluid
pooling, such as the paracolic, perihepatic, and infracolic spaces.
We noted a correlation between the presence of a retrovesical mass,
lymphadenopathy, and ascites. All patients who had ascites and lymphadenopathy
also had masses in the retrovesical or rectouterine spaces; two patients with
no ascites and lymphadenopathy had no masses in the retrovesical spaces. Liver
metastases also correlated strongly with the presence of a retrovesical mass.
In five (83.4%) of six patients with liver metastases, dominant retrovesical
masses were present. Although one could speculate that the presence of a
retrovesical mass might indicate an advanced stage of disease, we could not
find any correlation between a retrovesical mass and survival rate
(Table 1).
Previous descriptions of initial chest CT findings in DSRCT at the time of
diagnosis are limited [4]. Most
chest CT findings have been described on follow-up studies
[7,
8]. Unlike reports by Tateishi
et al. [4], pleural
dissemination was a relatively uncommon finding (25%) in our series. Four
(50%) of the eight patients displayed chest lymph node involvement, usually
internal mammary or paracardiac. Paracardiac lymph node involvement has also
been known to occur from dissemination of other abdominal tumors, such as
colon and ovary carcinomas. Contrary to previous reports, no pulmonary
parenchymal nodules were seen in our patients. Hematogenic dissemination in
DSRCT thus seems to occur less often within the chest than within the abdomen.
Lack of pathologic confirmation of findings on chest CT limits the study;
however, recognizing the aggressiveness of the abdominopelvic tumor, we
presume that those findings in the chest likely represent metastatic disease.
Metastases to bones, adrenal glands, kidneys, and spleen did not occur.
The differential diagnosis for DSRCT includes tumors, often malignant, that
produce bulky mesenteric masses, such as rhabdomyosarcoma, lymphoma,
neuroblastoma, PNET, mesothelioma, peritoneal leiomyosarcomatosis, and
intraabdominal desmoid tumor. A diagnosis of DSRCT usually can be favored by a
combination of factors, including adolescent age at presentation; frequent
tumor calcification; extensive peritoneal involvement at the time of
diagnosis; absence of an organ of origin; and, from our experience, a
proclivity to involve the retrovesical region. Rhabdomyosarcoma usually
affects younger children (70% are younger than 10 years old), and although
intraperitoneal involvement can be seen (in approximately 10%), mesenteric
nodules and intraperitoneal masses are typically smaller than those seen in
DSRCT; tumor calcification is uncommon
[10]. Burkitt's lymphoma,
unlike DSRCT, shows a predilection to the ileocecal region; omental or serosal
nodules and calcification are not common features
[11]. Neuroblastoma can
present as a pelvic mass but typically affects younger children (mean age at
time of diagnosis is 22 months, with 79% of diagnoses occurring before the age
of 4 years). PNET can appear like DSRCT if it arises in the pelvis,
retroperitoneum, or abdomen. Like DSCRT, PNET is an aggressive tumor with a
predilection for adolescents and young adults. The imaging findings of PNET
are similar to those of DSRCT, although fine tumor calcification is rarely
seen. Malignant mesothelioma rarely occurs during the first two decades of
life, and only approximately 15% of cases originate in the peritoneum
[12]. Peritoneal
leiomyosarcomatosis tends to occur in patients older than 24 years, with
multiple well-defined peritoneal nodules or mesenteric masses. Because a known
primary gastrointestinal leiomyosarcoma is not always apparent,
differentiation from DSRCT might be difficult. Intraabdominal desmoid tumors
are a rare, benign proliferation of musculoaponeurotic fibrous tissue that can
present in isolation or in association with Gardner's syndrome. The usual
presentation is isolated or multiple masses with attenuation less than or
similar to that of muscle tissue in the mesentery, abdominal wall,
retroperitoneum, and pelvis. The absence of metastases and association with
Gardner's syndrome should assist in this differential diagnosis.
Despite aggressive treatment, including surgical debulking, radiation
therapy, and multiagent chemotherapy, the prognosis in DSRCT is poor. The mean
survival is 17 months [7]. In
our series, eight patients died between 12 and 48 months after the initial
diagnosis (mean survival, 23 months).
In conclusion, DSRCT is a rare tumor, most commonly presenting in
adolescence, with significant radiologic features that can allow the
radiologist to suggest the diagnosis and differentiate it from other
intraperitoneal tumors. In particular, the presence of a dominant,
heterogeneous solid mass in the retrovesical space, along with omental,
mesenteric, or peritoneal surface masses, is a striking characteristic feature
of DSRCT. Unfortunately, most patients come to clinical attention when the
disease is at an advanced stage and has disseminated, especially to the liver
and to the retroperitoneal and mediastinal lymph nodes.
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Abstract
Introduction
