Colon tumor
Mesenchymal tumors
Reactive nodular fibrous pseudotumor

Author: Charanjeet Singh, M.D. (see Authors page)

Revised: 4 January 2017, last major update May 2012

Copyright: (c) 2003-2017,, Inc.

PubMed search: reactive nodular fibrous [title] pseudotumor colon

Cite this page: Reactive nodular fibrous pseudotumor. website. Accessed July 23rd, 2017.
Definition / general
  • First described in 2003 in 5 patients (Am J Surg Pathol 2003;27:532)
  • Mean age 56 years, range 48 to 71 years
  • Associated with prior abdominal surgery
  • At other sites, associated with endometriosis and ergotamine derivatives (Virchows Arch 2005;447:879)
  • May be related to a proliferation of multipotential subserosal cells (Int J Surg Pathol 2004;12:365)
  • Symptoms: acute abdominal pain, abdominal mass or incidental lesion
  • Genetics: despite staining for CD117, there are no substitutions, deletions or insertions in exon 11 or exon 9 of c-kit
Case reports
  • Complete resection appears curative
Gross description
  • Multiple or solitary tumors, usually involving outer wall of small intestine or colon
  • Firm, tannish white, 3 - 10 cm and well circumscribed
Microscopic (histologic) description
  • Low to moderately cellular, composed of stellate or spindled fibroblasts arranged haphazardly or in intersecting fascicles
  • May have infiltrative borders
  • Stroma rich in collagen (wire-like, keloidal or hyalinized)
  • Sparse intralesional mononuclear cells and peripheral lymphoid aggregates are usually present
Negative stains
Electron microscopy description
  • Myofibroblasts
Differential diagnosis
  • Retroperitoneal fibrosis: disease of retroperitoneum, associated with Reidel's sclerosing thyroiditis, methylsergine
  • Sclerosing mesenteritis: involves mesentery or mesocolon, mean 10 cm but up to 40 cm, usually no prior trauma, thick collagen bands dissecting lobules of mesenteric fat with fat necrosis