Colon
Mesenchymal tumors
Reactive nodular fibrous pseudotumor
Author: Raul S. Gonzalez, M.D.
Last author update: 17 February 2021
Last staff update: 10 May 2022
Copyright: 2003-2024, PathologyOutlines.com, Inc.
PubMed Search: reactive nodular fibrous pseudotumor
Table of Contents
Definition / general | Essential features | Sites | Etiology | Clinical features | Case reports | Treatment | Clinical images | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Negative stains | Molecular / cytogenetics description | Sample pathology report | Differential diagnosis | Board review style question #1 | Board review style answer #1Cite this page: Gonzalez RS. Reactive nodular fibrous pseudotumor. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/colontumorreactivenodular.html. Accessed April 23rd, 2024.
Definition / general
- Reactive fibroinflammatory process involving the gastrointestinal tract and mesentery (Am J Surg Pathol 2003;27:532)
Essential features
- Benign fibroinflammatory mass more common in men
- Stains for AE1 / AE3, CD117 and muscle specific actin
- Does not appear to recur
Sites
- Usually arises in mesentery; may involve colon or small bowel
Etiology
- May be related to a proliferation of multipotential subserosal cells (Int J Surg Pathol 2004;12:365)
- Possibly linked to endometriosis and ergotamine use (Virchows Arch 2005;447:879)
Clinical features
- Usually occurs in patients aged 40 - 60; more common in men
- Associated with prior abdominal surgery
- Can cause acute abdominal pain but sometimes discovered incidentally
Case reports
- 71 year old man with history of abdominal surgery and a 19.5 cm abdominal mass (Iran J Pathol 2015;10:149)
Treatment
- Complete resection appears curative
Clinical images
Images hosted on other servers:
Protruding lesion on back wall of gastric cardia
Gross description
- Solitary or multiple tumors, usually involving outer wall of small intestine or colon
- Firm, tan white, well circumscribed
- Usually around 6 cm but may measure up to 20 cm
Gross images
Images hosted on other servers:
Cut surface of lesion
Excised specimen in cut section
Fibrotic nodules in pouch of Douglas
Microscopic (histologic) description
- Mildly to moderately cellular lesion composed of stellate or spindled fibroblasts arranged haphazardly or in intersecting fascicles
- Stroma rich in collagen (wire-like, keloidal or hyalinized)
- Sparse intralesional mononuclear cells and peripheral lymphoid aggregates usually present
- May have infiltrative borders
Microscopic (histologic) images
Contributed by Raul S. Gonzalez, M.D.
Low power
Intermediate power
Interaction with adjacent fat
Entrapped nerves
Positive stains
Molecular / cytogenetics description
- No substitutions, deletions or insertions in exons 9 or 11 of KIT gene
Sample pathology report
- Mesentery, resection:
- Reactive fibrotic nodule, most consistent with reactive nodular fibrous pseudotumor (2.2 cm)
- Negative for malignancy.
- Margins of resection unremarkable.
Differential diagnosis
- Fibromatosis:
- Positive for beta catenin, negative for CD117
- Retroperitoneal fibrosis:
- Disease of retroperitoneum, associated with Riedel thyroiditis and methylsergine, negative for CD117
- Sclerosing mesenteritis:
- Involves mesentery or mesocolon, usually no prior trauma, thick collagen bands dissecting lobules of mesenteric fat with fat necrosis, negative for CD117
Board review style question #1
Which of the following abdominal lesions stains positive for CD117 by immunohistochemistry?
- Desmoid fibromatosis
- Inflammatory myofibroblastic tumor
- Reactive nodular fibrous pseudotumor
- Retroperitoneal fibrosis
- Sclerosing mesenteritis
Board review style answer #1
C. Reactive nodular fibrous pseudotumor
Comment here
Reference: Reactive nodular fibrous pseudotumor
Comment here
Reference: Reactive nodular fibrous pseudotumor
