Desmoplastic small round cell tumor (DSRCT) is a rare but aggressive peritoneal neoplasm typically seen in young males (15-35 years). Characterized by multifocal peritoneal/omental masses, massive ascites, and early widespread peritoneal dissemination. EWS-WT1 fusion transcript is pathognomonic. Prognosis is very poor — 5-year survival approximately 15-25%. CT shows multifocal peritoneal and omental solid masses, heterogeneous enhancement, and calcification. Treatment involves multi-agent chemotherapy + aggressive surgery + radiotherapy combination.
Age Range
10-35
Peak Age
22
Gender
Male predominant
Prevalence
Rare
DSRCT is an aggressive tumor carrying EWS-WT1 translocation t(11;22)(p13;q12). This fusion protein simultaneously activates tumor suppressor and oncogenic pathways. Tumor cells show small round cell morphology and reside within dense desmoplastic stroma — this stroma creates solid mass appearance on CT. Multifocal peritoneal growth pattern reflects tumor's affinity for peritoneal surfaces and transperitoneal dissemination tendency. Heterogeneous enhancement reflects tumor neovascularization and central necrosis areas. Calcification seen in 20-40% of cases from dystrophic calcification or osteoid metaplasia. Ascites results from increased vascular permeability from peritoneal irritation and lymphatic obstruction.
Calcification within multifocal peritoneal/omental solid masses in young male patient (15-35 years). As calcification is rare in peritoneal tumors, this combination strongly suggests DSRCT. Diagnostic value is high when clinical context (age, gender) and imaging findings (calcification, multifocality) are evaluated together.
Multifocal peritoneal and omental solid masses — numerous (5-50+), varying sizes (1-20 cm), dominant mass usually pelvic in location. Heterogeneous enhancement — peripheral solid component enhances, center remains necrotic. Masses adherent to peritoneal surfaces with widespread distribution involving mesentery and omentum.
Report Sentence
Multifocal heterogeneously enhancing solid masses on peritoneal and omental surfaces; DSRCT should be considered in young male patient context.
Coarse or punctate calcification within mass — seen in 20-40% of DSRCT cases. As calcification is rare in peritoneal tumors, this finding strongly suggests DSRCT. Calcification pattern is heterogeneous with scattered distribution within mass.
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Calcifications within peritoneal mass, supporting DSRCT diagnosis in young male patient context.
Heterogeneous signal on T2 — solid component intermediate-high signal, necrotic areas markedly hyperintense, desmoplastic stroma hypointense. Mixed signal pattern of masses reflects heterogeneous histological composition of DSRCT.
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Heterogeneous T2 signal in peritoneal masses on MRI, reflecting solid, necrotic, and desmoplastic components.
Avid FDG uptake in multifocal masses on PET-CT (SUVmax typically >5). Metabolic activity change is critical parameter in treatment response monitoring. PET-CT valuable for detecting extraperitoneal metastases (liver, lung, bone).
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Avid FDG uptake in multifocal peritoneal masses on PET-CT, high metabolic activity suggesting aggressive tumor.
Marked diffusion restriction in solid components on DWI — hyperintense on high b-value, hypointense on ADC. Low ADC values (<0.8 × 10⁻³ mm²/s) reflect high cellularity. No diffusion restriction in necrotic areas.
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Marked diffusion restriction in solid components of peritoneal masses on DWI, suggesting high cellularity.
Hepatic metastases seen in 30-50% of DSRCT cases. Multiple, heterogeneously enhancing solid lesions. Hepatic metastases together with peritoneal disease indicate disease extent and advanced stage.
Report Sentence
Multiple heterogeneously enhancing lesions in liver, consistent with metastases in context of peritoneal disease.
Criteria
Dominant peritoneal/omental involvement, massive ascites, multifocal masses. Most common presentation. No primary organ involvement — peritoneum is primary site.
Distinct Features
Multifocal peritoneal masses, omental cake-like involvement, massive ascites
Criteria
Liver, lung, bone, or lymph node metastases in addition to peritoneal disease. More advanced stage and worse prognosis. Extraperitoneal disease present in 30-50% at diagnosis.
Distinct Features
Liver/lung/bone metastases, widespread disease, poor prognosis
Criteria
Rare extra-abdominal locations — paratesticular, pleural, sinonasal, CNS, or other sites. Same histological and molecular features (EWS-WT1). Rarer than intra-abdominal form.
Distinct Features
Extra-peritoneal location, same molecular profile, rare
Distinguishing Feature
Peritoneal carcinomatosis typically in older patients with known primary tumor; DSRCT shows primary peritoneal involvement in young males with calcification
Distinguishing Feature
Peritoneal lymphomatosis shows homogeneous soft tissue thickening while DSRCT shows distinct solid masses with calcification; lymphoma has B symptoms and retroperitoneal lymphadenopathy
Distinguishing Feature
Extragonadal germ cell tumor usually single retroperitoneal or mediastinal mass with elevated AFP/β-hCG; DSRCT characterized by multifocal peritoneal masses and EWS-WT1 fusion
Distinguishing Feature
Extraintestinal GIST usually solitary large mass, KIT/DOG1 positive responding to imatinib; DSRCT multifocal masses with EWS-WT1 fusion
Urgency
emergentManagement
medicalBiopsy
NeededFollow-up
specialist-referralDSRCT is a rare aggressively behaving tumor — early biopsy and multidisciplinary approach are critical. Definitive diagnosis made by EWS-WT1 fusion transcript. Treatment involves P6 protocol (multi-agent chemotherapy) + aggressive cytoreductive surgery + whole abdominal radiation therapy (WART). Prognosis is poor but aggressive multimodal treatment can extend median survival to 2-3 years. Clinical trial referral recommended.
DSRCT is an extremely aggressive tumor with poor prognosis (5-year survival 15-25%). Multimodal treatment (chemotherapy + debulking surgery + radiotherapy) is applied. EWSR1-WT1 gene fusion confirms diagnosis. New targeted therapies and immunotherapy are under investigation.