Mesenteric desmoid tumor (aggressive fibromatosis) is a benign but locally aggressive fibroblastic neoplasm arising from myofibroblast proliferation. Does not metastasize but has high local recurrence rate. Strong association with Gardner syndrome (FAP variant) — develops in 10-20% of FAP patients. Sporadic form may arise at surgical scar or trauma site. Appears as well-defined or infiltrative solid mesenteric mass on CT. May encase mesenteric vessels and cause bowel obstruction.
Age Range
20-55
Peak Age
35
Gender
Female predominant
Prevalence
Rare
Desmoid tumors arise from clonal proliferation of myofibroblasts and are associated with mutations in the beta-catenin/Wnt signaling pathway. In FAP patients, APC gene mutation impairs beta-catenin degradation and increases cell proliferation. Tumor produces dense collagen matrix — this fibrous tissue appears as solid mass on CT and determines T2 signal characteristics on MRI: collagen-dense areas appear T2 hypointense, cellular areas T2 hyperintense. Enhancement reflects neovascularization and vascularity of cellular areas. Mesenteric desmoids may invade bowel wall and encase mesenteric vessels causing ischemia. Locally aggressive behavior reflects tendency to infiltrate surrounding tissues without metastatic potential.
Mixed signal pattern on MR T2 with hypointense collagen bands and hyperintense cellular areas within mass. Collagen-dense bands produce low signal creating linear hypointense areas within tumor. This pattern is highly characteristic of desmoid tumor and used as reference in treatment response monitoring — collagen increases with treatment and T2 hypointensity becomes more prominent.
Well-defined or infiltrative solid mass in mesentery. Shows homogeneous or heterogeneous enhancement. Size ranges 2-20 cm. Calcification is rare. Mass may encase mesenteric vascular structures. Fat plane obliteration around mass indicates infiltrative growth.
Report Sentence
Solid mass in mesentery observed; desmoid tumor (aggressive fibromatosis) should be considered in the context of FAP/Gardner syndrome.
Heterogeneous/mixed signal on T2 — collagen-dense areas appear as distinctly hypointense bands, cellular and edematous areas appear hyperintense. This 'band-like' T2 hypointensity pattern is highly characteristic of desmoid tumor. With treatment response, collagen content increases and T2 signal decreases.
Report Sentence
Mixed signal on T2 in mesenteric mass — hypointense collagen bands and hyperintense cellular areas, consistent with desmoid tumor.
Encasement of mesenteric vessels (SMA, SMV) by tumor. Vessel lumen usually remains patent (occlusion is rare) but vessel contours become irregular. This finding is critical in surgical planning — vascular encasement determines resectability. 'Comb sign' — comb-teeth appearance of encased mesenteric vessels.
Report Sentence
Mesenteric mass encases SMA/SMV branches; vascular mapping is needed for surgical planning.
Variable diffusion restriction on DWI — cellular areas show restriction, collagen-dense areas do not. ADC values are heterogeneous. In treatment response monitoring, ADC increase (decreased cellularity) indicates favorable response.
Report Sentence
Diffusion restriction in cellular areas of the mass on DWI, consistent with active desmoid tumor.
Solid, hypoechoic or heterogeneous mass in abdomen on US. Borders may be well-defined or irregular. May show internal vascularity on Doppler. US diagnostic value is limited — CT and MRI preferred for characterization.
Report Sentence
Solid hypoechoic mass in abdomen on US; CT/MRI recommended for further characterization.
Mass iso- or slightly hypointense to muscle on T1. Homogeneous or heterogeneous enhancement on contrast-enhanced series. Post-gadolinium enhancement degree proportional to cellularity and vascularity. Late-phase enhancement increase reflects contrast accumulation in collagen matrix.
Report Sentence
Mass isointense to muscle on T1 with progressive enhancement on contrast series, consistent with desmoid tumor.
Criteria
Mesenteric desmoid developing in FAP/Gardner syndrome background. Associated with APC gene mutation. Frequently develops after colectomy. May be multiple. Important cause of morbidity and mortality in FAP patients.
Distinct Features
FAP history, post-colectomy, may be multiple, APC mutation, aggressive behavior
Criteria
Sporadic desmoid tumor without FAP association. Associated with CTNNB1 (beta-catenin) somatic mutation. May develop at surgical scar or trauma site. Usually solitary. May show estrogen receptor positivity.
Distinct Features
No FAP history, surgical scar site, solitary, CTNNB1 mutation, may be estrogen-related
Criteria
Retroperitoneally located desmoid tumor. May invade psoas muscle or retroperitoneal structures. May cause ureteral obstruction. Can be confused with retroperitoneal sarcomas — biopsy needed for differential diagnosis.
Distinct Features
Retroperitoneal location, psoas invasion, ureteral obstruction, sarcoma differential
Distinguishing Feature
Mesenteric lymphoma typically shows homogeneous hypodense mass with 'sandwich sign'; desmoid tumor is solid enhancing mass with characteristic collagen bands on T2; B symptoms (fever, night sweats, weight loss) accompany lymphoma
Distinguishing Feature
Extraintestinal GIST is heterogeneous mass with necrosis and hemorrhage areas, KIT/DOG1 positive; desmoid shows collagen bands on T2 and is beta-catenin positive; GIST responds to imatinib while desmoid requires different treatment protocol
Distinguishing Feature
Retroperitoneal liposarcoma contains fat-density components (except dedifferentiated type); desmoid tumor is homogeneous soft tissue density without fat component; liposarcoma MDM2 positive, desmoid beta-catenin positive
Distinguishing Feature
Mesenteric carcinoid shows characteristic sunburst calcification and desmoplastic reaction; desmoid tumor rarely calcifies and shows collagen bands on T2; carcinoid may have elevated 5-HIAA and carcinoid syndrome
Urgency
routineManagement
medicalBiopsy
NeededFollow-up
6-monthTreatment paradigm for desmoid tumor has shifted — active surveillance (watch-and-wait) has become first-line approach as spontaneous regression occurs in 20-30%. For progressive or symptomatic disease, pharmacological treatment (NSAIDs, tamoxifen, sorafenib) or surgery is planned. Surgery requires wide resection but careful evaluation needed due to high local recurrence rate (20-60%). Genetic counseling and family screening critical in FAP patients. 6-month MRI follow-up assesses treatment response through T2 signal changes and size.
Desmoid tumor is locally aggressive but does not metastasize. FAP/Gardner syndrome screening should be performed. High recurrence rate after surgery. Medical therapy (NSAIDs, tamoxifen) may be effective in some cases.