Abdominal Desmoid Fibromatosis
Differential Diagnosis
- Scar
- Nodular fasciitis
- Proliferative myositis
- Desmoplastic fibroblastoma
- Intramuscular myxoma
- Plexiform fibrohistiocytic tumor
- Inflammatory myofibroblastic tumor
- Fibrosarcoma
- Low grade myxofibrosarcoma
- Desmoplastic melanoma
- Calcifying fibrous pseudotumor
Fibromatosis, Abdominal Desmoid, Extra-abdominal Desmoid, Mesenteric, Retroperitoneal and Pelvic | Scar |
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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, Abdominal Desmoid and Extra-abdominal Desmoid | Nodular Fasciitis |
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Usually dense collagenous stroma | Collagenous stroma focal or rare |
Linear fascicles of cells | Undulating bundles of cells |
Infrequent mitotic figures | Frequent mitotic figures |
Usually >3 cm | Usually <4 cm |
Beta-catenin 80-90% | Beta-catenin negative |
Fibromatosis, Abdominal Desmoid and Extra-abdominal Desmoid | Proliferative Myositis |
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Muscle fibers damaged or obliterated | Muscle fibers not damaged |
Muscle fibers at edge of lesion | Muscle fibers throughout |
No ganglion-like cells | Ganglion-like cells present |
Predominantly collagenous | Predominantly myxoid |
Usually >3 cm | Usually <4 cm |
Fibromatosis, Abdominal Desmoid and Extra-abdominal Desmoid | Desmoplastic Fibroblastoma |
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Mild to moderate cellularity | Paucicellular |
Moderate vascularity | Hypovascular |
Extensive infiltration of muscle | Only focal muscle infiltration |
Spindle cells usually in fascicular pattern | Spindle and stellate cells randomly aranged |
Fibromatosis, Abdominal Desmoid and Extra-abdominal Desmoid | Intramuscular Myxoma |
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Mild to moderate cellularity | Markedly hypocellular |
Areas with collagen | No collagen |
Prominent vessels | Sparse vessels |
Fibromatosis, Abdominal Desmoid and Extra-abdominal Desmoid | Plexiform Fibrohistiocytic Tumor |
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Deep to subcutis, in muscle | Superficial |
Generally solid mass | Plexiform architecture |
Rare under 3 cm | Rare over 3 cm |
Giant cells and histiocytes rare | Nodules of giant cells and histiocytes |
Fibromatosis, Abdominal Desmoid, Extra-abdominal Desmoid, Mesenteric, Retroperitoneal and Pelvic | Inflammatory Myofibroblastic Tumor |
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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, Abdominal Desmoid and Extra-abdominal Desmoid | Adult Fibrosarcoma |
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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 |
Fibromatosis, Abdominal Desmoid, Extra-abdominal Desmoid, Mesenteric, Retroperitoneal and Pelvic | Myxofibrosarcoma |
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No pleomorphism | Cytologic pleomorphism present |
Usually dense stroma but focally may be myxoid | No dense stroma |
Vessels lack arching pattern | Arching vessels |
Fibromatosis, Abdominal Desmoid and Extra-abdominal Desmoid | Desmoplastic Melanoma |
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Based below subcutis, involves muscle | Usually based in dermis |
S100 negative | S100 positive |
Fibromatosis, Abdominal Desmoid and Extra-abdominal Desmoid | Calcifying Fibrous Pseudotumor |
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Nearly always has cellular areas | Uniformly paucicellular |
Infiltrative pattern prominent | Microscopically infiltrative at most |
No calcification | Calcification present |
Inflammation uncommon | Chronic inflammation present |