Surgical Pathology Criteria–

Mesenteric Fibromatosis

Differential Diagnosis

Fibromatosis, Abdominal Desmoid, Extra-abdominal Desmoid, Mesenteric, Retroperitoneal and Pelvic Scar
Uniform Multiple stages of organization
Hemosiderin rare Hemosiderin common
Rare under 3 cm Rare over 3 cm
Inflammation not prominent Inflammation may be prominent
Usually infiltrates muscle Infiltration of muscle uncommon

 

Fibromatosis, Mesenteric, Retroperitoneal and Pelvic Sclerosing Mesenteritis
Scant inflammation Prominent inflammatory component
Fibrous mass with peripheral infiltration Surrounds and entraps fat
Fat necrosis infrequent Fat necrosis frequent
Beta-catenin positive (nuclear) Beta-catenin negative

 

Fibromatosis, Mesenteric, Retroperitoneal and Pelvic Retroperitoneal Fibrosis
Scant inflammation Prominent inflammatory component
Forms a mass Diffuse, usually no mass lesion
Rarely involves both ureters Medial deviation of both ureters
Stroma diffusely collagenous Broad bands of hyalinized collagen

 

Fibromatosis, Mesenteric or Retroperitoneal and Pelvic Gastrointestinal Stromal Tumor
CD34 negative CD34 60-70% positive
CD117 frequently negative, variable reports of focal/weak staining CD117 74-95% positive
DOG1 negative DOG1 87-94%
Beta-catenin positive 90% (nuclear) Beta-catenin negative
Low to moderate cellularity Moderate to high cellularity
Cytologically bland May be cytologically atypical
Prominent thin walled dilated veins Lacks prominent veins
Infiltrative margin Usually circumscribed, pushing margin
No cystic degeneration or necrosis May have cystic degeneration or necrosis
GIST with epithelioid or abundant spindled cytoplasm can be distinguished morphologically

 

Fibromatosis, Mesenteric or Retroperitoneal and Pelvic Gastric Plexiform Fibromyxoma
Long fascicles of cells No fascicles
Myxoid pattern rare Myxoid pattern predominates
Areas of dense collagen frequent Lacks dense collagen
Usually extrinisc mass invading bowel wall Intrinsic to bowel wall
CD117 frequently negative, variable reports of focal/weak staining CD117 74-95% positive
DOG1 negative DOG1 87-94%

 

Fibromatosis, Abdominal Desmoid, Extra-abdominal Desmoid, Mesenteric, Retroperitoneal and Pelvic Inflammatory Myofibroblastic Tumor
Rare <12 years of age Age usually <14, rare >30
Inflammation not prominent Prominent inflammation, particularly plasma cells
Alk1 negative Alk1 frequently positive
Beta catenin 80-90% Beta catenin negative

 

Fibromatosis, Mesenteric, Retroperitoneal and Pelvic Adult Fibrosarcoma
Intra-abdominal Very rare in abdominal cavity
Mild to moderate cellularity Usually more cellular
Fine chromatin Usually clumped chromatin
Rarely >5 mitotic figures / hpf Usually >5 mitotic figures / hpf
Rarely necrotic Frequent necrosis
Distinction between grade I fibrosarcoma and fibromatosis may not always be clear

 

Fibromatosis, Abdominal Desmoid, Extra-abdominal Desmoid, Mesenteric, Retroperitoneal and Pelvic Myxofibrosarcoma
No pleomorphism Cytologic pleomorphism present
Usually dense stroma but focally may be myxoid No dense stroma
Vessels lack arching pattern Arching vessels

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