Desmoid tumor pathophysiology

Desmoid tumor Microchapters
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Case #1

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Sara Mohsin, M.D.[2]Faizan Sheraz, M.D. [3]

Overview

Desmoid tumor may occur as part of Gardner syndrome. A minority of desmoid tumors are associated with Turcot syndrome, Familial adenomatous polyposis, and estrogen therapy.

Pathophysiology

Their exact aetiology remains uncertain, although they are frequently associated with previous trauma or surgical incision. On the molecular level, desmoids are characterised by mutations in the β-catenin gene, CTNNB1, or the adenomatous polyposis coli gene, APC.

Associated Diseases

• Some cases have been associated with estrogen therapy
• Turcot syndrome
• Gardner syndrome
• Familial adenomatous polyposis
  • In the case of mesenteric desmoid they are seen either sporadically or in association with familial polyposis coli syndrome(FAP)

Gross Pathology

• Abdominal wall desmoid tumors arise from:

• Musculoaponeurotic structures of the abdominal wall (especially the rectus and internal oblique muscles and their fascial coverings)
• External oblique muscle and the transversalis muscle or fascia

• These masses have a firm, gritty texture. On the cut surface, they are glistening white and coarsely trabeculated, resembling scar tissue

Location

Frequent locations in the abdomen are:

• Abdominal wall
• Root of the mesentery
• Retroperitoneum

Microscopic Pathology

Histologically, desmoid tumors consist of:

• Elongated fibroblasts.
• Myofibroblasts characterized by elongated, tapered cytoplasm; elongated, vesicular, typical-appearing nuclei; and multiple small nucleoli. The cells are linearly arranged and are surrounded and separated from each other by collagen.
• These tumors show a tendency to evolve over time.
• Vandevenne et al described three stages of evolution of desmoid tumors:

• In the first stage, lesions are more cellular and have fewer areas of hyalinized collagen.
• In the second stage, there is an increasing amount of collagen deposition in the central and peripheral areas of the tumor.
• In the third stage, there is an increase in the fibrous composition with a decrease in cellularity and water content.