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Colon tumor

Mesenchymal tumors

Fibromatosis of colon

Reviewers: Charanjeet Singh, M.D. (see Reviewers page)
Revised: 26 March 2012, last major update March 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
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● Also called intraabdominal desmoid tumor
● Uncommon, usually in mesentery or retroperitoneum
● Rarely adheres to or penetrates colonic wall
● Mean age 34 years (younger than GIST patients)
● May be associated with trauma, familial adenomatous polyposis, Gardner’s syndrome, Lynch syndrome (Cancer 1992;69:2049) and hormonal stimulation
● Locally aggressive (benign, but may recur)

Molecular genetics:
● Associated with mutations in APC gene, therefore leads to alteration of beta-catenin pathway
● This manifests as aberrant nuclear expression of beta-catenin rather than its usual membranous positivity

Case reports
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● 6 day old boy with solitary colonic tumor (Eur J Pediatr Surg 2002;12:337)
● 9 year old boy with intraabdominal tumor with invasion of colonic wall (Eur J Pediatr Surg 2005;15:196)
● 22 year old woman with inoperable recurrence causing death (Vojnosanit Pregl 2006;63:839)
● 38 year old woman with Turner’s syndrome (Kurume Med J 1999;46:181)
● 72 year old man with colonic mesenteric tumor causing acute abdomen (Indian J Gastroenterol 2002;21:199)

Treatment
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● Surgical excision, radiation therapy and possibly chemotherapy

Gross description
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● Firm, tan and homogenous
● Usually large (6 to 25 cm) with infiltrative margins

Micro description
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● Broad, sweeping fascicles of bland spindle cells with overall minimal mitotic activity (mean 4 mitoses / 50 HPF), bland nuclear features and finely collagenous stroma
● Infiltrative borders, evenly spaced blood vessels
● May involve muscularis propria but no necrosis, no hemorrhage, no myxoid degeneration, no epithelioid cells, no pleomorphism, no foam cells
● Periphery may show prominent lymphoid aggregates, but no inflammatory cells within tumor or around vessels

Micro images
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Bland spindle cells with evenly spaced blood vessels

Positive stains
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● Vimentin, CD117 (some antibodies), smooth muscle actin, desmin (50%) and beta-catenin (nuclear staining)

Negative stains
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● CD34, S100

Electron microscopy description
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● Myofibroblastic / fibroblastic differentiation

Differential diagnosis
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● GIST: positive for CD117, negative for beta-catenin (Am J Surg Pathol 2000;24:947)
● Post-surgical nodular fasciitis: short fascicles with extravasation of red cells, positive for desmin
● Sclerosing mesenteritis: areas of fat necrosis and perivascular infiltrates of lymphoid cells

End of Colon tumor > Mesenchymal tumors > Fibromatosis of colon

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